Table 2

Mental health outcome variables
Variable Cohort questionnaire item Response categories Categories in present study
Yes No
Current stress Stress means a situation when a person feels tense, restless, nervous, or anxious or is unable to sleep at night because his/her mind is troubled all the time. Are you currently experiencing this kind of stress? a = not at all, b = just a little, c = to some extent, d = quite a lot, e = very much d–e a–c
Sleep disturbances How often have you had problems with your sleep these past 30 days (e.g., difficulties falling asleep, repeated awakenings, waking up too early)? a = never, b = a few times per month, c = several times per week, and d = every day c–d a–b
Symptoms of depressionone itemtwo items During the past month, have you often been bothered by: (a) little interest or pleasure in doing things? (b) feeling down, depressed, or hopeless? Yes or No One item:(a) Yes or(b) YesTwo items:(a) Yes and(b) Yes One item:(a) No and(b) NoTwo items:(a) No and(b) No
Reduced performance Have the following complaints influenced your performance at work or in studies over the past 14 days? (a) stress/depressed mood? (b) tiredness a = No, b = Yes, negligibly, c = Yes, a little, and d = Yes, quite a lot (a) d or(b) d (a) a–c and(b) a–c

Thomée et al.

Thomée et al. BMC Psychiatry 2012 12:176   doi:10.1186/1471-244X-12-176

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