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Open Access Research article

Long-term neurocognitive effects of methylphenidate in patients with attention deficit hyperactivity disorder, even at drug-free status

Yu-Shu Huang12, Liang-Jen Wang23 and Chih-Ken Chen234*

Author Affiliations

1 Department of Child Psychiatry and Sleep Center, Chang Gung Memorial Hospital at Linko, Taoyuan, Taiwan

2 Chang Gung University School of Medicine, Taoyuan, Taiwan

3 Department of Psychiatry, Chang Gung Memorial Hospital at Keelung, Keelung, Taiwan

4 Department of Psychiatry, Chang Gung Memorial Hospital at Keelung, No.200 Lane 208, Ji-Jin 1st Road, Anle District, Keelung City, 204, Taiwan, R.O.C

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BMC Psychiatry 2012, 12:194  doi:10.1186/1471-244X-12-194

Published: 9 November 2012

Abstract

Background

Methylphenidate (MPH), a psycho-stimulant, is the most widely administered drug for the pharmacological management of patients with attention deficit hyperactivity disorder (ADHD). This study attempts to determine whether sustainable improvements occur in neurocognitive function among ADHD patients following 12-month treatment with MPH, at drug-free status. Whether age groups, gender or ADHD subtypes differ in neurocognitive performance during MPH treatment is also examined.

Methods

Study participants consisted of 103 ADHD patients (mean age: 9.1 ± 1.9 years old) who were drug naïve or drug free for at least 6 months. The patients were prescribed oral short-acting MPH at each dose range of 0.3–1.0 mg/kg daily. During 12 months of the study, the patients underwent the test of variables of attention (TOVA) at the baseline, month 6 and month12. Patients were instructed to not intake MPH for one week before the second and the third TOVA.

Results

Seventy five patients completed the study. Results of this study indicated that although commission errors and response sensitivity (d’) significantly improved during MPH treatment for 12 months, omission errors, response time, response time variability and ADHD score did not. While younger ADHD patients (<9 y/o) performed better in response time, response time variability, d’ and ADHD score than older ones (≥9 y/o), the latter more significantly improved in response time than the former during 12 months of treatment. Additionally, boys improved more than girls in omission error and d’. Moreover, although ADHD subtypes significantly differed in ADHD score during the treatment, MPH treatment and ADHD subtypes did not interact with each other for all TOVA indices.

Conclusions

ADHD patients significantly improved in impulsivity and perceptual sensitivity, determined as TOVA, during MPH treatment for 12 months. Age and gender, yet not ADHD subtypes, appear to influence the MPH treatment effects in some indices of TOVA. A future study containing a comparison group is suggested to confirm whether the neurocognitive improvements are attributed to long-term effects of MPH or natural maturation of patients.

Keywords:
ADHD; Cognition; Methylphenidate; Neuropsychological test; Subtypes; Predictor