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Open Access Highly Accessed Research article

Psychopathic traits and offender characteristics – a nationwide consecutive sample of homicidal male adolescents

Nina Lindberg14*, Taina Laajasalo2, Matti Holi3, Hanna Putkonen4, Ghitta Weizmann-Henelius4 and Helinä Häkkänen-Nyholm25

Author Affiliations

1 Helsinki University Central Hospital, Department of Adolescent Psychiatry, PO Box 590, 00029 HUS/HYKS, Helsinki, Finland

2 Department of Psychology, PO Box 9, 00014 University of Helsinki, Finland

3 Kellokoski Hospital, 04500 Kellokoski, Finland

4 Vanha Vaasa Hospital, PO Box 13, 65381 Vaasa, Finland

5 Forensic Laboratory, National Bureau of Investigation, PO Box 285, 01301 Vantaa, Finland

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BMC Psychiatry 2009, 9:18  doi:10.1186/1471-244X-9-18


The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1471-244X/9/18


Received:26 January 2009
Accepted:6 May 2009
Published:6 May 2009

© 2009 Lindberg et al; licensee BioMed Central Ltd.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background

The aim of the study was to evaluate psychopathy-like personality traits in a nationwide consecutive sample of adolescent male homicide offenders and to compare the findings with those of a randomly sampled adult male homicide offender group. A further aim was to investigate associations between psychopathic traits and offender and offence characteristics in adolescent homicides.

Methods

Forensic psychiatric examination reports and crime reports of all 15 to19- year- old male Finnish offenders who had been subjected to a forensic psychiatric examination and convicted for a homicide during 1995–2004 were collected (n = 57). A random sample of 57 adult male homicide offenders was selected as a comparison group. Offence and offender characteristics were collected from the files and a file-based assessment of psychopathic traits was performed using the Hare Psychopathy Checklist-Revised (PCL-R) by trained raters.

Results

No significant differences existed between the adolescents and adults in PCL-R total scores, factor 2 (social deviance) scores, or in facets 3 (lifestyle) and 4 (antisocial). Adults scored significantly higher on factor 1 (interpersonal/affective) and facets 1 (interpersonal) and 2 (affective). The adolescent group was divided into two subgroups according to PCL-R total scores. One in five homicidal male adolescents met criteria for psychopathic personality using a PCL-R total score of 26 or higher. These boys significantly more often had a crime history before the index homicide, more frequently used excessive violence during the index homicide, more rarely lived with both parents until 16 years of age, had more institutional or foster home placements in childhood, had more school difficulties, more often had received special education, and, more often had contact with mental health services prior to age 18 years than boys scoring low on the PCL-R. They also more often had parental criminal history as well as homicide history of parents or near relatives than the group scoring low on the PCL-R.

Conclusion

Homicidal boys behaved as antisocially as the homicidal adults. The adults, however, showed more both affective and interpersonal features of psychopathy. Homicidal adolescents with psychopathy-like personality character form a special subgroup among other homicidal youngsters. Recognizing their characteristics, especially in life course development, would facilitate effective prevention and intervention efforts.

Background

Among Western European nations, Finland has an exceptionally high rate of homicide. In 2006, the total rate per 100,000 inhabitants of homicidal crimes reported to the police was 2.6 [1] in a population of 5.3 million [2]. The annual number of police-reported homicides has varied between 100 and 155 during the last ten years [3]. The rates per capita have for decades been about double the rate of the most of the other West European democracies and triple the rate of the other Nordic countries [4]. Approximately 9% of homicides each year are committed by individuals aged less than 20 years [5]. As many as 92% of the young homicidal offenders are boys [6].

According to a recent study on Finnish homicidal adolescents [7], approximately 50% were diagnosed as having a conduct disorder or a personality disorder, while 7% of these offenders suffered from schizophrenia. Sixty-four percent of the adolescents were intoxicated by alcohol and 21% were under the influence of drugs at the time of the killing; however, as many as 32% of the offenders were considered not to suffer from a mental illness or substance abuse. The motive "robbery" was high [7] suggesting that among adolescent homicide offenders acts of instrumental violence are more frequent. About one-third of homicides committed by adolescents are carried out by two or more perpetrators [6]. Excessive violence has been shown to be related to adolescent homicides, suggesting an unambivalent need to maximize injuries [8] or a tendency to show off to peers [7].

Psychopathy is defined as a constellation of affective, interpersonal, and behavioral characteristics including impulsivity, irresponsibility, shallow emotions, lack of empathy, guilt, or remorse, pathological lying, and persistent violation of social norms and expectations [9-11]. At the interpersonal level, psychopathic individuals have been described as grandiose, arrogant, callous, dominant, superficial, and manipulative. Affectively, they are short-tempered, unable to form strong emotional bonds with others, and lacking in guilt or anxiety. These interpersonal and affective features are associated with a socially deviant lifestyle that includes irresponsible behavior and a tendency to ignore or violate social conventions and mores [10]. Although not all persons with psychopathy come into contact with the criminal system, their defining features place them at high risk for aggression and violence [12]. Offenders with psychopathy typically begin their antisocial and criminal activities at a relatively young age and continue to engage in these activities throughout their lifespan [13]. In addition, their use of violence tends to be more instrumental, dispassionate, and predatory than that of other offenders [14]. Psychopathy has also been repeatedly associated with sadistic and sexual violence [15]. Psychopathic criminals re-offend more quickly, more often, and more violently following release from custody than do other offenders [16]. Victims of offenders with psychopathy are less often family members and more often strangers than is the case with other nonpsychopathic violent offenders [17]. In addition to antisocial personality disorder, psychopathy is associated with alcohol and drug abuse and dependency [18,19]. Usually, a negative correlation or no correlation with the presence of a major mental disorder is recorded [18,20]. However, prevalence of psychopathy among seriously violent offenders with schizophrenia is elevated, being as high as 20% [21-23].

Most authors consider adult psychopathy to stem from conduct problems exhibited earlier in life [24], and childhood traumatization has repeatedly been associated with psychopathic development [25-27], but the utility of the psychopathy construct has been questioned for youths by some researchers because of its likelihood to be less stable, the weight that the label carries for poor prognosis, and the lack of prospective longitudinal research [28-30]. A recent follow-up study has, however, found that adolescent psychopathic features are quite stable [31], and depending on the nature of the sample and the instrument used to assess psychopathy, as many as 9–59% of adolescent offenders have been reported to have psychopathy- like personality character [26]. Youngsters with psychopathic traits commit more violent acts [32], re-offend more quickly than other antisocial adolescents [33], and their offences are more serious than in other antisocial youths [34]. So, in this sense, juvenile psychopathy resembles adult psychopathy [35].

The aim of this study was to evaluate psychopathy-like personality traits in a nationwide consecutive sample of adolescent male homicide offenders and to compare these findings with a randomly sampled adult gender-matched homicide offender group. Our hypothesis was that despite the difference in age, in the perspective of psychopathy these two groups would not differ from each other. The other aim of the study was to investigate associations between adolescent psychopathic traits and offender and offence characteristics. Our hypotheses were that adolescents with psychopathy-like personality character would more often have previous crime history, more often suffer from conduct disorder/antisocial personality disorder and drug problems, significantly more frequently use excessive violence in their killing, more often act with co-offenders, more often direct violence to strangers, and, that motive for violence would more often be instrumental. We also examined connections between adolescent psychopathic traits and life course development. We hypothesised that homicidal adolescents with psychopathic personality character would report more childhood trauma.

Methods

Sample

The material of the present study was register-based and nationwide. In Finland, the mean clearance rate for homicide was 92% during 1995–2004 [2]. Information concerning homicides and the offenders was obtained from the Finnish National Authority for Medicolegal Affairs (NAMA), which organizes the forensic psychiatric examinations in Finland. According to Finnish law, courts decide whether a forensic examination is needed. After deciding on the examination, the court asks NAMA to arrange it. Forensic psychiatric examinations are inpatient evaluations lasting six weeks on average, and include data gathered from various sources (family members, relatives, and medical, criminal, school, and military records), psychiatric evaluation, standardized psychological tests, interviews conducted by a multiprofessional team, evaluation of the offender's physical condition and continuous observation of the offender by hospital staff. The final forensic psychiatric report includes an opinion on the level of criminal responsibility, a possible psychiatric diagnosis, and an assessment as to whether or not the offender fulfils the criteria for involuntary psychiatric care. As part of a large research project on Finnish homicides led by author HH, forensic psychiatric examination reports of all offenders prosecuted for a homicide perpetrated in 1995–2004 and who had been subjected to a forensic psychiatric examination were collected from the archives of NAMA. Between 1995–2004 a total of 1046 people were charged with homicide offences [2], 749 of whom were referred to a forensic psychiatric examination. These 749 offenders were prosecuted for 700 homicidal events with a total of 757 victims. Of these offenders, 66 (9%) were 15–19-years old at the time of the killing (note: in Finland, the minimum age of criminal liability is 15 years). Later, collection of subjects' criminal records from the Legal Register Center showed that six of these 15- to 19- year-olds were eventually not convicted for the homicide (but rather for aggravated assault, for instance) or did not have a criminal record (e.g. due to being deceased). These cases were excluded from the data leaving us with a sample of 57 boys and 3 girls. After excluding the girls (due to an extremely small number) the final data comprised 57 male adolescents (mean age 17.6 years, SD 1.25). Of the remaining offenders in the national data, a random sample of 57 adult males (mean age 37.6 years, range 20–59, SD 10.81) convicted of a homicide served as the comparison group. NAMA, the Legal Register Center and the Ministry of the Interior approved the study protocol.

Measures

Assessment of psychopathy-like personality character was performed using the 20-item Hare Psychopathy Checklist-Revised (PCL-R) [10], which has become the standard for assessing psychopathy in forensic settings. The PCL-R is thus a reliable and valid instrument for measuring psychopathy [36-40], and its psychometric properties appear to be much the same across countries [39]. Although the PCL-R was originally constructed for use with adult male criminal offenders, it has been shown to be functional in the assessment of male juvenile delinquents as well [41,42]. Due to the comparison with an adult sample, the youth version of PCL-R (PCL-R:YV) [43] was not applicable here. Specific scoring criteria were used to rate each PCL-R item on a three-point scale (0 = absent,1 = possibly or partially present, 2 = definitely present) according to the extent to which it applies to a given individual. The PCL-R items are summed to yield total scores ranging from zero to 40; scores of 30 and higher are considered diagnostic of psychopathy [44]. In line with recommendations of a lower cut-off score for European populations [40,45,46], a cut-off score of 26 has often been used in studies performed in Scandinavian countries [47,48]. The PCL-R is underpinned by two factors that tap affective-interpersonal features (factor 1: glibness and superficial charm, grandiose sense of self-worth, pathological lying, manipulative behavior, lack of remorse or guilt, shallow affect, lack of empathy, failure to accept responsibility) and socially deviant lifestyle and behaviors (factor 2: proneness to boredom, parasitic lifestyle, poor behavioral controls, lack of realistic, long-term goals, impulsivity, irresponsibility, juvenile delinquency, revocation of conditional release). Factor 1 can be separated into two facets; interpersonal (facet 1) and affective (facet 2), as can factor 2; lifestyle (facet 3) and antisocial (facet 4). Although PCL-R assessments are recommended to be based on both a review of file information and an semistructured interview with the offender, research has consistently shown that assessments based solely on file information are highly similar to those including an interview, and, provided that there is sufficient file information, are appropriate in the absence of an interview, especially for research purposes [36,49-51].

Procedure

Forensic psychiatric examination reports were retrospectively reviewed. As PCL-R/PCL-R:YV is not applied in the standard hospital examinations, the reports were retrospectively scored using the PCL-R by trained raters, all of whom were either forensic psychiatrists or psychologists. Further, to evaluate inter-rater agreement on PCL-R ratings, 20 reports were randomly chosen from the total national data and rated by all raters after workshop attendance and several training sessions. The inter-rater agreement was assessed using intraclass correlation (ICC). The ICC was 0.898 for PCL-R total score, 0.735 for factor 1 score and 0.920 for factor 2 score. All correlations were significant (p < 0.001). The internal consistency, as measured by Cronbach's alpha, was 0.89 for all items, 0.86 for factor 1, and 0.79 for factor 2, 0.84 for facet 1, 0.83 for facet 2, 0.87 for facet 3, and 0.64 for facet 4.

Demographic data, family related characteristics, problems related to school, information on psychiatric and criminal history as well as the index offences were gathered from the Finnish police computerized Criminal Index File and the forensic psychiatric evaluation reports. Diagnoses were made according to DSM-III-R [52] criteria until 1996, after which ICD-10 [53] was used together with DSM-IV [54]. According to Cloninger and Svrakic [55] diagnosis of specific personality disorder may be made in children and adolescents when observed maladaptive personality traits are pervasive, persistent, and unlikely to be limited to a particular developmental stage or an episode of an axis I disorder. Diagnosis of a personality disorder in an individual under 18 years of age requires that the features be present for more than 1 year. The only exception to this is antisocial personality disorder, which can not be diagnosed in individuals under 18 years of age. The overall quality and reliability of Finnish forensic psyhiatric examinations are considered high by both courts and scientists [56]. With regard to index violence, the cases needed to be coded for excessive violence. There is currently no uniform operational definition for excessive violence. However, excessive violence has been operationalised in two of our previous studies on homicides in reference to the mean number of stab wounds in the data as well as sadistic or sexual features [7,57]. Similar operational definition was used in the present study to allow comparison to our previous studies. Thus, with regard to index violence, the cases were classified as excessively violent if sadistic or sexual features, mutilation, more than three forms of violence, or more than 13 stab wounds (which was the mean number of stab wounds with a s.d. of 23.4) were present. Inter-rater reliability of the offence, victim, and offender related variables has been assessed in our previous studies, where the same data collection procedure and partly the same data were used [58,59]. Thus, only variables with substantial or perfect agreement [60] were included in this data.

Statistics

Data analyses were conducted with the SPSS 11.0.1. statistical software package. Chi-square analysis and Fisher's Exact Test were used to compare differences in frequencies between the groups. Differences in mean PCL-R scores were assessed by Mann-Whitney U-test. Findings were considered significant when p < 0.05. The Bonferroni correction was not used to control Type I errors due to the multiple comparisons, as it has been criticized for dramatically increasing the risk of Type II errors [61-63]. Instead, effect sizes are reported. For chi square analysis, the magnitudes of effect size phi were interpreted following the guidelines by Rea and Parker: 0.00 to under 0.10 – negligible association, 0.10 to under 0.20 – weak association, 0.20 to under 0.40 – moderate association, 0.40 to under 0.60 – relatively strong association, 0.60 to under 0.80 – strong association, and 0.80 to 1.00 – very strong association [64]. To assist in determining the meaningfulness of group effects, correlational effect size statistics were calculated by diving the z score by the square root of the number of participants contributing to the analyses. An effect size of r = 0.10 was defined as small, r = 0.30 as medium, and r = 0.50 as large [65].

Results

The mean age of victims of the adolescent group was 38.3 years (range 10–78, SD 19.01) and of the adult comparison group 40.3 years (range 3–85, SD 13.65). The difference between the groups was not significant.

The PCL-R total scores, factor scores, facet scores, and item-by-item scores are presented in Table 1. Because of the young age of the adolescents, the item " many short-term marital relationships" was excluded from the analyses.

Table 1. PCL-R mean (SD) total scores, factor scores, facet scores, and item-by-item scores of the homicidal male adolescents (n = 57) and the adult male comparison group (n = 57).

No significant differences existed between the adolescents and adults in PCL-R total scores, factor 2 (social deviance) scores, or in facets 3 (lifestyle) and 4 (antisocial). Adults scored significantly higher on factor 1 (interpersonal/affective) and facets 1 (interpersonal) and 2 (affective). No significant correlation existed between offender's age and PCL-R in adolescents. A negative correlation between offender's age and PCL-R total score in the comparison group was observed (Pearson r = -0.323, p = 0.014).

The adolescent sample was divided into two groups according to PCL-R total scores. 45 boys scored less than 26 points and 12 boys scored 26 or more points on the PCL-R. In order to analyse whether the two groups differ in terms of all of the PCL-R factors and facets, Table 2 presents the mean PCL-R scores for both groups. In addition, results are presented for the two groups with regard to diagnoses, crime scene behavior, victim-offender relationship, crime history, and life course development.

Table 2. Mean (SD) Factors, facets, clinical diagnoses, crime history, crime characteristics, victim-offender relationship, and life course development in homicidal male adolescents scoring low (total score < 26; n= 45) and high (total score ≥ 26; n= 12) on the PCL-R.

The boys scoring high on the PCL-R differed markedly from those scoring low on the PCL-R on both factors and all four facets. They significantly more often had a crime history before the index homicide, more frequently used excessive violence during the index homicide, more rarely lived with both parents until 16 years of age, had more institutional or foster home placements in childhood, had more school difficulties, more often had received special education, and, more often had contact with mental health services prior to age 18 years than boys scoring low on the PCL-R. They also more often had parental criminal history as well as homicide history of parents or near relatives than the group scoring low on the PCL-R.

Discussion

The aim of this study was to evaluate psychopathy-like personality traits in a nationwide consecutive sample of adolescent male homicide offenders and to compare these findings with a randomly sampled adult gender-matched homicide offender group. According to our hypothesis PCL-R total scores did not differ between the two groups. Homicidal boys as a group displayed highly antisocial behavior, and despite being approximately 20 years younger than the adult offenders, were as antisocial as the adult group. The adults, however, showed more both affective and interpersonal features of psychopathy. Many authors contend that psychopathic personality features – such as dishonesty, lack of guilt, or manipulativeness – are often present already in childhood [9,10,66,67], but interpersonal and affective features typically develop and strengthen over time in connection with other people [67]. This might explain why they were not as prominent in youths, with fairly limited social interaction networks, as in adults. In addition, this may explain the recent reports that young offenders with psychopathy-like personality character might be more malleable than adults and benefit more from treatment [68]. Another explanation for the difference could be that the affective-interpersonal features were similarly present in adolescents and adults, but were not noticed equally well by forensic investigators, who typically work in the field of adult psychiatry and are not experts in adolescent psychiatry. It is also noteworthy that in Finland approximately only one-tenth of forensic psychiatric examinations are performed on under-aged offenders. The affective-interpersonal aspects of psychopathy are typically more difficult to recognize than the behavioral ones and the difficulty may be even greater in youngsters. To better understand the transition from psychopathic features to adult psychopathy, more prospective longitudinal research is needed.

In line with the previous Finnish study [7], the mean age of the victims did not differ between the adolescents and the adult comparison group. This has been explained by two main reasons. Firstly, parents, stepparents as well as other adult quardians are often victims of under-aged homicide offenders, and, secondly, robbery is one of the most frequent motives among adolescent killers [6]. Among Finnish adults, a typical homicide victim is an adult drinking partner [5]. The other aim of the present study was to investigate associations between adolescent psychopathic traits and offender and offence characteristics. The adolescent sample was divided into two groups according to PCL-R total scores. Approximately one in five Finnish homicidal male adolescents showed psychopathy-like personality character using the PCL-R with the recommended cut-off score of 26 for Scandinavian populations. There is continuous ongoing discussion on whether antisocial and criminal behaviors are parts of the psychopathy syndrome. In a recent study by Andershed et al. [69], the three-factor model of psychopathy by Cooke and Michie [70], which excludes aspects of criminal behavior, was shown to be useful in identifying a problematic subgroup of young offenders. In the present study, boys with psychopathy-like personality character differed markedly from those scoring low on the PCL-R on both factors and all four facets. Thus, differences between the groups cannot be explained only by differences in antisocial and criminal behaviors but also by both affective and interpersonal features, which are often known as the "core" of psychopathy [9]. Many studies among children and adolescents indicate that these affective-interpersonal traits foreshadow the greatest risk of long-term maladjustment [71-73].

Boys with psychopathy-like personality character significantly more often had a previous crime history than boys scoring low on the PCL-R. This result is in agreement with many previous reports showing that adolescents with psychopathic traits differ from other antisocial youths in age of onset of criminal career and likelihood of recidivism [33-35,74,75].

In line with previous studies on Finnish adolescent homicide offenders, our results suggest that abuse of alcohol or drugs, personality disorders, and social maladjustment characterize young offenders [6,7]. In accordance with the results for adult populations and for some earlier studies among young offenders [41,70,76], adolescents scoring high on the PCL-R seemed to have a tendency to suffer from conduct disorder/antisocial personality disorder as well as from other personality disorders and substance abuse/dependence more often than adolescents scoring low on the PCL-R.

The degree of cruelty in a homicide is difficult to measure, and a finding of brutality is subjective, varying across time and place. In our study, the use of excessive violence in killing was significantly more frequent in boys with psychopathy-like personality character than in boys scoring low on the PCL-R. Despite our conservative criteria for excessive violence, almost 40% of the boys scoring high on the PCL-R were classified into this category. The finding is similar to that reported in adult populations and is consistent with the study by Murrie et al. [77], in which PCL-YV psychopathy scores correlated with measures of severity of violence among juvenile male offenders. Also, in the recent study by Kruh et al. [78], affective-interpersonal features of psychopathy-like personality character predicted more frequent use of sadistic violence, repeated violence against the same victim, and violence resulting in more serious victim injuries.

Adolescents with either childhood-onset or adolescent-onset conduct disorder have equally high levels of delinquent peer affiliation [79], but youngsters with both conduct problems and affective-interpersonal features of psychopathy-like personality character show the highest level of affiliation with deviant peers [80]. In line with these earlier findings, a tendency was observed that boys scoring high on the PCL-R more often committed a homicide together with one or more co-offenders than boys scoring low on the PCL-R.

In accord with previous studies among adolescent homicide offenders, acts of instrumental violence were very common. In line with a study by Kruh et al. [78] there was some positive association between instrumental violence and psychopathy-like personality character but it failed to reach a statistically significant level and the effect size was only moderate.

One of the aims of the study was to examine connections between adolescent psychopathic traits and life course development because adverse family conditions and early traumatization are commonly regarded as risk factors for aggressive and violent behavior [81,82], and high victimization subjects have been reported to have high PCL-R scores in adulthood [25]. In our study, boys with high psychopathy-like personality character more rarely lived with both parents until the age of 16 years and had more institutional or foster home placements in childhood than boys scoring low on the PCL-R. This is in line with a recent study by Campbell et al. [26], in which a history of nonparental living arrangements (e.g. foster care) predicted higher PCL-YV scores among a sample of incarcerated adolescent offenders. Correlations between high PCL-R scores and broken homes as well as between psychopathy and single-parent families have also been reported earlier [83,84]. In line with previous studies [27,28,85], there was some positive association between parental alcohol abuse, mental health problems, physical abuse and psychopathy-like personality character but it failed to reach a statistically significant level and the effect size was only moderate. Although the quality of parenting generally predicts externalizing behavior, according to some recent research [85-87], ineffective parenting might be less relevant in explaining behavioral problems of children with callous-unemotional traits of psychopathy-like personality character. The connection between parental history of antisocial behavior and child conduct problems has been well documented [88,89]. Recent studies have also revealed strong evidence of inter-generational transmission of criminality from parents to offsprings [90,91]. Here, boys with psychopathy-like personality character significantly more often had parental criminal history as well as homicide history of parents or near relatives than boys scoring low on the PCL-R. The finding is in accordance with Christian et al. [92] and Frick et al. [93], who found that children with conduct problems and features of psychopathy were more likely to have parents with a history of antisocial personality disorder as well as fathers with an arrest history than children with conduct problems only.

Severe antisocial behavior has often been demonstrated to be associated with low intelligence [94,95]. Recent studies, however, suggest that youths with psychopathic traits do not show the verbal intelligence deficits generally associated with conduct problems, and the relationships between psychopathic features and nonverbal intelligence have not been clearly identified [34]. In our study, all adolescent homicidal offenders scoring high on the PCL-R had experienced school difficulties and received special education, and in this sense they differed significantly from boys scoring low on the PCL-R. Both school difficulties and the need for special education are typically based on either medical, psychological, social, or intellectual factors, but we were unable to specify individual reasons. The issue is clearly important and warrants future research.

Adult psychopathy is often described as incurable syndrome [96], and from the perspective of adult psychiatry, it would be important and cost-effective to identify those at risk of psychopathic behavior as early as possible. In our study, up to 75% of the boys with psychopathy-like personality character had had some contact with mental health services – via either child or adolescent psychiatry – prior to the index homicide. Better recognition of childhood trauma and other characteristics of youngsters with psychopathic traits would facilitate effective prevention and intervention efforts. The families with risk factors need extensively help and the children protection for avoiding the "cycle of adverse experiences" as well as the "cycle of violence" [97]. In addition, there is some new evidence that young offenders with psychopathy-like personality character might be more malleable than adults and benefit more from treatment [68].

A strength of this study was its nationwide comprehensive nature. The high Finnish clearance rate for homicide, the tradition of thorough forensic psychiatric examinations, and reliable statistics form a solid basis for register-based study. However, the fact that the present study was retrospective and register-based does present some obvious limitations, though the same limitations apply both the adolescents and the comparison group. Unfortunately, it was not possible to estimate the representativeness of the whole sample by comparing the number of offenders in the present sample with the number of overall adolescent homicide. In a previous Finnish study [7], it was estimated that 60% of 15–17-year old homicide suspects go through the forensic examination. The selection bias applying both the adolescents and the comparison group is, however, a clear limitation of the study, and must be kept in mind. In addition, regardless of the fact that the adolescent sample consisted of all homicidal boys who underwent forensic psychiatric examinations and were convicted in 1995–2004, the number of subjects remained small and the results must be regarded as indicative. One must also remember that the concept of psychopathy is not an established medical diagnosis, and its applicability to emotionally immature adolescents from deprived backgrounds serves further studies. Also, the observed effect sizes were not large, with phi's falling mostly into category of moderate effect size [64]. Finally, due to multiple comparisons, there is a possibility that statistical significance was declared where no association exists (type I error).

Conclusion

Homicidal boys behaved as antisocially as the homicidal adults. The adults, however, showed more both affective and interpersonal features of psychopathy. Homicidal adolescents with psychopathy-like personality character form a special subgroup among other homicidal youngsters. Recognizing their characteristics, especially in life course development, would facilitate effective prevention and intervention efforts.

Competing interests

NL has received travel funds from Novartis and NL and HH-N from BMS during 2008.

The other authors declare no competing interests.

Authors' contributions

NL reviewed the forensic psychiatric statements, scored for the PCL-R, organized data, and served as the first author. TL analyzed data. MH participated in the writing process. HP participated in the writing process. GW-H reviewed the forensic psychiatric statements, scored the PCL-R, and participated in the writing process. HH-N provided the material, contributed with ideas and context, and participated in the writing process.

Acknowledgements

The last author (HH-N) would like to express her gratitude to the Academy of Finland for grant numbers 75697 and 211176. All authors are grateful to the National Authority for Medicolegal Affairs, the Ministry of the Interior, and the Legal Register Center, for providing data. Many thanks to Camilla Hagelstam, Mikko Ylipekka, and Tuija Rovamo for assisting with data collection.

References

  1. Kivivuori J, Lehti M, Aaltonen M: Homicide in Finland 2002–2006. A Description Based on the Finnish Homicide Monitoring System (FHMS). [http://www.optula.om.fi/uploads/coixzx0dv6vk7ih.pdf] webcite

  2. National Statistics 2007 [http://www.statistics.gov.uk/cci/nugget.asp?ID=6] webcite

  3. Lehti M, Kivivuori J: Kuolemaan johtanut väkivalta. In Rikollisuustilanne 2005. Rikollisuus ja seuraamusjärjestelmä tilastojen valossa (English Summary: Crime and Criminal Justice in Finland). Helsinki: Hakapaino Oy; 2006:13-41. OpenURL

  4. Salfati CG: A European perspective on the study of homicide.

    Homicide Stud 2001, 5:286-291. OpenURL

  5. Lehti M: Henkirikoskatsaus 2002 (English Summary: Homicides, Homicide Offenders and Victims in Finland in 1998–2002). National Research Institute of Legal Policy. Research Reports. Helsinki: Hakapaino Oy; 2004. OpenURL

  6. Lehti M: Nuorten henkirikokset. In Nuorisorikollisuus: Määrä, syyt ja kontrolli (English Summary: Juvenile Crime in Finland: Trends, Causes and Control). Edited by Honkatukia P, Kivivuori J. Helsinki: Hakapaino Oy; 2006:57-96. OpenURL

  7. Hagelstam C, Häkkänen H: Adolescent homicides in Finland: offence and offender characteristics.

    Forensic Sci Int 2006, 164:110-115. PubMed Abstract | Publisher Full Text OpenURL

  8. Bailey S: Adolescents who murder.

    J Adolesc 1996, 19:19-39. PubMed Abstract | Publisher Full Text OpenURL

  9. Cleckley H: The Mask of Sanity. 5th edition. St. Louis: MO; 1976. OpenURL

  10. Hare RD: The Hare Psychopathy Checklist – Revised. Toronto: Multi-Health Systems; 1991. OpenURL

  11. Hare RD: Psychopaths and their nature: Implications for the mental health and criminal justice systems. In Psychopathy: Antisocial, Criminal, and Violent Behaviour. Edited by Millon T, Simonson E, Burket-Smith M, Davis R. New York: Guilford Press; 1998:188-212. OpenURL

  12. Hart SD, Hare RD: Psychopathy: assessment and association with criminal conduct. In Handbook of Antisocial Behavior. Edited by Stoff DM, Maser J, Brieling J. New York: Wiley; 1997:22-35. OpenURL

  13. Forth AE, Burke HC: Psychopathy in adolescence: assessment, violence, and developmental precursors. In Psychopathy: Theory, Research, and Implications for Society. Edited by Cooke DJ, Forth AE, Hare RD. Dordrecht: Kluver; 1998:205-229. OpenURL

  14. Hart SD, Dempster RJ: Impulsivity and psychopathy. In Impulsivity: New Directions in Research and Clinical Practice. Edited by Webster CD, Jackson MA. New York: Guilford; 1997:212-232. OpenURL

  15. Hare RD, Cooke DJ, Hart SD: Psychopathy and sadistic personality disorder. In Oxford Textbook of Psychopathology. Edited by Millon T, Blaney PH, Davis RD. NewYork: Oxford University Press; 1999:555-584. OpenURL

  16. Salekin RT, Rogers R, Sewell KW: A review and meta-analysis of the Psychopathy Checklist and Psychopathy Checklist-Revised: Predictive validity of dangerousness.

    Clin Psychol 1996, 3:203-215. OpenURL

  17. Weizmann-Henelius G, Viemerö V, Eronen M: The violent female perpetrator and her victim.

    Forensic Sci Int 2003, 133:197-203. PubMed Abstract | Publisher Full Text OpenURL

  18. Hildebrand M, de Ruiter C: PCL-R psychopathy and its relation to DSM-IV Axis I and II disorders in a sample of male forensic psychiatric patients in The Netherlands.

    Int J Law Psychiatry 2004, 27:233-248. PubMed Abstract | Publisher Full Text OpenURL

  19. Söderström H, Nilsson T, Sjodin AK, Carstedt A, Forsman A: The childhood-onset neuropsychiatric background to adulthood psychopathic traits and personality disorders.

    Compr Psychiatry 2005, 46:111-116. PubMed Abstract OpenURL

  20. Hart SD, Hare RD: Discriminant validity of the Psychopathy Checklist in a forensic psychiatric population.

    Psychol Assess 1989, 1:211-218. OpenURL

  21. Nolan KA, Volavka J, Mohr P, Czobor P: Psychopathy and violent behavior among patients with schizophrenia or schizoaffective disorder.

    Psychiatr Serv 1999, 50:787-792. PubMed Abstract | Publisher Full Text OpenURL

  22. Abushua'leh K, Abu-Akel A: Association of psychopathic traits and symptomatology with violence in patients with schizophrenia.

    Psychiatry Res 2006, 143:205-211. PubMed Abstract | Publisher Full Text OpenURL

  23. Tengström A, Grann M, Långström N, Kullgren G: Psychopathy (PCL-R) as a predictor of violent recidivism among criminal offenders with schizophrenia.

    Law Hum Behav 2000, 24:45-58. PubMed Abstract | Publisher Full Text OpenURL

  24. Saltaris C: Psychopathy in juvenile offenders. Can temperament and attachment be considered as robust developmental precursors?

    Clin Psychol Rev 2002, 22:729-752. PubMed Abstract OpenURL

  25. Lang S, af Klinteberg B, Alm PO: Adult psychopathy and violent behavior in males with early neglect and abuse.

    Acta Psychiatr Scand Suppl 2002, (412):93-100. PubMed Abstract OpenURL

  26. Campbell MA, Porter S, Santor D: Psychopathic traits in adolescent offenders: an evaluation to criminal history, clinical, and psychosocial correlates.

    Behav Sci Law 2004, 22:23-47. PubMed Abstract | Publisher Full Text OpenURL

  27. Krischer MK, Sevecke K: Early traumatization and psychopathy in female and male juvenile offenders.

    Int J Law Psychiatry 2008, 31:253-262. PubMed Abstract | Publisher Full Text OpenURL

  28. Edens JF, Skeem JL, Cruise KR, Caufmann E: Assessment of "juvenile psychopathy" and its association with violence: A critical review.

    Behav Sci Law 2001, 19:53-80. PubMed Abstract | Publisher Full Text OpenURL

  29. Seagrave D, Grisso T: Adolescent development and the measurement of juvenile psychopathy.

    Law Hum Behav 2002, 26:219-239. PubMed Abstract | Publisher Full Text OpenURL

  30. Steinberg L, Scott ES: Less quilty by reason of adolescence: Developmental immaturity, diminished responsibility, and the juvenile death penalty.

    Am Psychol 2003, 58:1009-1018. PubMed Abstract | Publisher Full Text OpenURL

  31. Loney BR, Taylor J, Butler MA, Iacono WG: Adolescent psychopathy features: 6-year temporal stability and the prediction of externalizing symptoms during the transition to adulthood.

    Aggress Behav 2007, 33:242-252. PubMed Abstract | Publisher Full Text OpenURL

  32. Frick PJ, Cornell AH, Barry CT, Bodin SD, Dane HA: Callous- unemotional traits and conduct problems in the prediction of conduct problem severity, aggression, and self-report of delinquency.

    J Abnorm Child Psychol 2003, 31:457-470. PubMed Abstract | Publisher Full Text OpenURL

  33. Långström N, Grann M: Psychopathy and violent recidivism among young criminal offenders.

    Acta Psychiatr Scand Suppl 2002, (412):86-92. PubMed Abstract OpenURL

  34. Kotler JS, McMahon RJ: Child psychopathy: Theories, measurement, and relations with the development and persistence of conduct problems.

    Clin Child Fam Psychol Rev 2005, 8:291-325. PubMed Abstract | Publisher Full Text OpenURL

  35. Lynam DR, Gudonis L: The development of psychopathy.

    Annu Rev Clin Psychol 2005, 1:381-407. PubMed Abstract | Publisher Full Text OpenURL

  36. Grann M, Långström N, Tengström A, Stålenheim E: Reliability of file-based retrospective ratings of psychopathy with the PCL-R.

    J Pers Assess 1998, 70:416-426. PubMed Abstract OpenURL

  37. Gacono CB, Hutton HE: Suggestions for the clinical and forensic use of the Hare Psychopathy Checklist-Revised (PCL-R).

    Int J Law Psychiatry 1994, 17:303-317. PubMed Abstract | Publisher Full Text OpenURL

  38. Fulero S: Review of the Hare Psychopathy Checklist-Revised. In Twelfth Mental Measurements Yearbook. Edited by Conoley JC, Impara JC. Nebraska: Buros Institute; 1998:453-454. OpenURL

  39. Stone G: Review of the Hare Psychopathy Checklist-Revised. In Twelfth mental measurements yearbook. Edited by Conoley JC, Impara JC. Nebraska: Buros Institute; 1998:454-455. OpenURL

  40. Hare RD, Clark D, Grann M, Thornton D: Psychopathy and the predictive validity of the PCL-R: in international perspective.

    Behav Sci Law 2000, 18:623-645. PubMed Abstract | Publisher Full Text OpenURL

  41. Forth AE, Hart SD, Hare RD: Assessment of psychopathy in male young offenders.

    Psychol Assess 1990, 2:342-344. OpenURL

  42. Smith SS, Newman JP: Alcohol and drug abuse/dependence disorders in psychopathic and nonpsychopathic criminal offenders.

    J Abnorm Psychol 1990, 99:430-439. PubMed Abstract | Publisher Full Text OpenURL

  43. Forth AE, Kosson DS, Hare RD: The Hare PCL:YV. Toronto: Multi-Health Systems; 2003. OpenURL

  44. Hare RD: The Hare Psychopathy Checklist – Revised. 2nd edition. Toronto: Multi-Health Systems; 2003. OpenURL

  45. Cooke DJ, Michie C: Psychopathy across cultures: North America and Scotland compared.

    J Abnorm Psychol 1999, 108:58-68. PubMed Abstract | Publisher Full Text OpenURL

  46. Sullivan EA, Abramowitz CS, Lopez M, Kosson DS: Reliability and construct validity of the psychopathy checklist -revised for Latino, European American, and African American male inmates.

    Psychol Assess 2006, 18:382-292. PubMed Abstract | Publisher Full Text OpenURL

  47. Grann M, Långström N, Tengström A, Kullgren G: Psychopathy (PCL-R) predicts violent recidivism among criminal offenders with personality disorders in Sweden.

    Law Hum Behav 1999, 23:205-217. PubMed Abstract | Publisher Full Text OpenURL

  48. Rasmussen K, Storsaeter O, Levander S: Personality disorders, psychopathy, and crime in a Norwegian prison population.

    Int J Law Psychiatry 1999, 22:91-97. PubMed Abstract OpenURL

  49. Wong S: Is Hare's Psychopathy Checklist reliable without the interview?

    Psychol Rep 1988, 62:931-934. PubMed Abstract OpenURL

  50. Mossman D: Assessing predictions of violence: Being accurate about accuracy.

    J Consult Clin Psychol 1994, 62:783-792. PubMed Abstract | Publisher Full Text OpenURL

  51. Alterman AI, Cacciola JS, Rutherford MJ: Reliability of the Revised Psychopathy Checklist in substance abuse patients.

    Psychol Assess 1993, 5:442-448. OpenURL

  52. American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders revised. 3rd edition. Washington DC: American Psychiatric Association; 1987. OpenURL

  53. World Health Organization: The ICD-10 Classification of Mental and Behavioural disorders: Clinical Descriptions and Diagnostic Guidelines. Geneva: World Health Organization; 1992. OpenURL

  54. American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders. 4th edition. Washington DC: American Psychiatric Association; 1994. OpenURL

  55. Cloninger CR, Svrakic DM: Personality Disorders. In Comprehensive Textbook of Psychiatry. Volume II. 7th edition. Edited by Sadock BJ, Sadock VA. Philadelphia: Lippincott Williams & Wilkins; 2000::1723-1764. OpenURL

  56. Eronen M, Repo E, Vartiainen H, Tiihonen J: Forensic Psychiatric Organization in Finland.

    Int J Law Psychiatry 2000, 23:541-546. PubMed Abstract | Publisher Full Text OpenURL

  57. Laajasalo T, Häkkänen H: Excessive violence and psychotic symptomatology among homicide offenders with schizophrenia.

    Crim Behav Ment Health 2006, 16:242-253. PubMed Abstract | Publisher Full Text OpenURL

  58. Häkkänen H, Laajasalo T: Homicide crime scene actions in a Finnish sample of mentally ill offenders.

    Homicide Studies 2006, 10:33-54. OpenURL

  59. Laajasalo T, Häkkänen H: Background characteristics of mentally ill homicide offenders – a comparison of five diagnostic groups.

    J Forensic Psychiatr Psychol 2004, 15:451-474. OpenURL

  60. Brennan PF, Hays BJ: The Kappa statistics for establishing inter-rater reliability in the secondary analysis of quantitative clinical data.

    Res Nurs Health 1992, 15:153-158. PubMed Abstract OpenURL

  61. Moran MD: Arguments for rejecting the sequential Bonferroni in ecological studies.

    Oikos 2003, 102:403-405. OpenURL

  62. Nakagawa S: A farewell to Bonferroni: the problems of low statistial power and publication bias.

    Behavioral Ecology 2004, 15:1044-1045. OpenURL

  63. Perneger TV: What's wrong with Bonferroni adjustments.

    BMJ 1998, 316:1236-1238. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  64. Rea LM, Parker RA: Designing and conducting survey research. San Francisco: Jossey-Boss; 1992. OpenURL

  65. Rosenthal R: Meta-analytic procedures for social research (revised). Newbury Park, CA: Sage; 1991. OpenURL

  66. Hare RD: Psychopathy: A clinical construct whose time has come.

    Crim Justice Behav 1996, 23:25-54. OpenURL

  67. Forsman M, Lichtenstein P, Andershed H, Larsson H: Genetic effects explain the stability of psychopathic personality from mid- to late adolescence.

    J Abnorm Psychol 2008, 117:606-617. PubMed Abstract | Publisher Full Text OpenURL

  68. Caldwell M, Skeem J, Salekin R, Van Rybroek G: Treatment response of adolescent offenders with psychopathy features. A 2-year follow-up.

    Crim Justice Behav 2006, 33:571-596. OpenURL

  69. Andershed H, Köhler D, Eno Louden J, Hinrichs G: Does the three-factor model of psychopathy identify a problematic subgroup of young offenders?

    Int J Law Psychiatry 2008, 31:189-198. PubMed Abstract | Publisher Full Text OpenURL

  70. Cooke DJ, Michie C: Refining the construct psychopathy: Towards a hierarchic model.

    Psychol Assess 2001, 13:171-188. PubMed Abstract | Publisher Full Text OpenURL

  71. Hare RD: Without conscience: The disturbing world of the psychopaths among us. 1st edition. New York: Pocket Books; 1993. OpenURL

  72. Frick PJ, Cornell AH, Bodin SD, Dane HA, Barry CT, Loney RB: Callous- unemotional traits and developmental pathways to severe conduct problems.

    Dev Psychol 2003, 39:246-260. PubMed Abstract | Publisher Full Text OpenURL

  73. Pardini DA, Loeber R: Special section: Interpersonal and affective features of psychopathy in children and adolescents: Advancing a developmental perspective.

    J Clin Child Adolesc Psychol 2007, 36:269-275. PubMed Abstract OpenURL

  74. Gretton H, McBride M, Hare RD, O'Shaughnessy R, Kumka G: Psychopathy and recidivism in adolescent sex offenders.

    Crim Justice Behav 2001, 28:427-449. OpenURL

  75. Gretton H, Hare RD, Catchpole R: Psychopathy and offending from adolescence to adulthood: A ten-year follow-up.

    J Consult Clin Psychol 2004, 72:636-645. PubMed Abstract | Publisher Full Text OpenURL

  76. Mailloux DL, Forth AE, Kroner DG: Psychopathy and substance use in adolescent male offenders.

    Psychol Rep 1997, 81:529-530. PubMed Abstract OpenURL

  77. Murrie DC, Cornell DG, Kaplan S, McConville D, Levy-Elkon A: Psychopathy scores and violence among juvenile offenders: a multi-measure study.

    Behav Sci Law 2004, 22:49-67. PubMed Abstract | Publisher Full Text OpenURL

  78. Kruh IP, Frick PJ, Clements CB: Historical and personality correlates to the violence patterns of juveniles tried as adults.

    Crim Justice and Behav 2005, 32:69-96. OpenURL

  79. Moffitt TE, Caspi A, Dickson N, Silva P, Stanton W: Childhood -onset versus adolescent -onset antisocial conduct problems in males: Natural history from ages 3 to 18 years.

    Dev Psychopathol 1996, 1:105-118. OpenURL

  80. Kimonis ER, Frick PJ, Barry CT: Callous-unemotional traits and delinquent peer affiliation.

    J Consult Clin Psychol 2004, 72:956-966. PubMed Abstract | Publisher Full Text OpenURL

  81. Jaffee SR, Caspi A, Moffitt TE, Taylor A: Physical maltreatment victim to antisocial child: Evidence of an environmentally mediated process.

    J Abnorm Psychol 2004, 113:44-55. PubMed Abstract | Publisher Full Text OpenURL

  82. Marmorstein NR, Iacono WG: Longitudinal follow-up of adolescents with late-onset antisocial behavior: A pathological yet overlooked group.

    J Am Acad Child Adolesc Psychiatry 2005, 44:1284-1291. PubMed Abstract | Publisher Full Text OpenURL

  83. Koivisto H, Haapasalo J: Childhood maltreatment and adulthood psychopathy in light of file-based assessments among mental state examinees.

    Studies on Crime and Crime Prevention 1996, 5:91-104. OpenURL

  84. Patrick CJ, Zempolich KA, Levenston GK: Emotionality and violent behavior in psychopaths: a biosocial analysis. In Biosocial bases of violence. Edited by Raine A, Brennan PA, Farrington DP, Mednick SA. New York: Plenum; 1996:145-161. OpenURL

  85. Oxford M, Cavell TA, Hughes JN: Callous/unemotional traits moderate the relationship between ineffective parenting and child externalizing problems: A practical replication and extension.

    J Clin Child and Adolesc Psychol 2003, 32:577-585. OpenURL

  86. Frick P, Marsee M: Psychopathy and developmental pathways to antisocial behavior in youth. In Handbook of psychopathy. Edited by Patrick C. New York: Guilford; 2006:353-374. OpenURL

  87. Edens JF, Skopp NA, Cahill MA: Psychopathic features moderate the relationship between harsh and inconsistent parental discipline and adolescent antisocial behavior.

    J Clin Child Adolesc Psychol 2008, 37:472-476. PubMed Abstract OpenURL

  88. Capaldi D, DeGarmo D, Patterson GR, Forgatch M: Contextual risk across the early life span and association with antisocial behavior. In Antisocial behavior in children and adolescents: A developmental analysis and model for intervention. Washington DC: American Psychological Association; 2002:123-146. OpenURL

  89. Frick PJ, Loney BR: Understanding the association between parent and child antisocial behavior. In The effects of parental dysfunction on children. Edited by McMahon RJ, Peters R DeV. NewYork: Kluwer Academic/Plenum Publishers; 2002:105-126. OpenURL

  90. Putkonen A, Ryynänen O-P, Eronen M, Tiihonen J: The quantitative risk of violent crime and criminal offending: a case control study among the offspring of recidivistic Finnish homicide offenders.

    Acta Psychiatr Scand Suppl 2002, (412):54-57. PubMed Abstract OpenURL

  91. Smith CA, Farrington DP: Continuities in antisocial behavior and parenting across three generations.

    J Child Psychol Psychiatry 2004, 45:230-247. PubMed Abstract | Publisher Full Text OpenURL

  92. Christian RE, Frick PJ, Hill NL, Tyler L, Frazer DR: Psychopathy and conduct problems in children: II. Implications for subtyping children with conduct problems.

    J Am Acad Child Adolesc Psychiatry 1997, 36:233-241. PubMed Abstract | Publisher Full Text OpenURL

  93. Frick PJ, O'Brien B, Wootton J, McBurnett K: Psychopathy and conduct problems in children.

    J Abnorm Psychol 1994, 103:700-707. PubMed Abstract | Publisher Full Text OpenURL

  94. Moffitt TE, Henry B: Neuropsychological studies of juvenile delinquency and juvenile violence. In Neuropsychology of aggression. Edited by Milner JS. Boston: Kluwer Academic; 1991:67-91. OpenURL

  95. Moffitt TE: Adolescence-limited and life-course persistent antisocial behavior: A developmental taxonomy.

    Psychol Rev 1993, 100:674-701. PubMed Abstract | Publisher Full Text OpenURL

  96. Salekin R: Psychopathy and therapeutic pessimism: Clinical lore or clinical reality?

    Clin Psychol Rev 2002, 22:79-112. PubMed Abstract OpenURL

  97. Maxfield MG, Widom CS: The cycle of violence. Revisited 6 years later.

    Arch Pediatr Adolesc Med 1996, 150:390-395. PubMed Abstract | Publisher Full Text OpenURL

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