|Mental health outcome variables|
|Variable||Cohort questionnaire item||Response categories||Categories in present study|
|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 depression one item two 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