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 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:	One item:
			(a) Yes or	(a) No and
			(b) Yes	(b) No
			Two items:	Two items:
			(a) Yes and	(a) No and
			(b) Yes	(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	(a) a–c and
			(b) d	(b) a–c