Depressive Symptoms

Demographic data included age (≥14 years), sex, marital and employment status, religion, migrant background, education and total income of household.
The German version of the PSS-10 (PSS-10; [10 (link)]) was used to measure the degree to which life in the past month has been experienced as unpredictable, uncontrollable and overwhelming (e.g. “In the last month, how often have you felt nervous and "stressed"?) on a 5-point response scale (0 = “never”, 1=”almost never”, 2=”sometimes”, 3=”fairly often”, 4=”very often”). The scale was forward translated from English to German and subsequently back translated by two interdependent bilingual speakers. After reversing the scores on the four positively stated items (Items 4, 5, 7, and 8), a PSS-10 total score was obtained by summing up all 10 items. Higher scores indicated a higher level of perceived stress. As the PSS is not a diagnostic instrument, there are no cut-off scores.
In addition to the PSS-10, socio-demographic questions and additional psychological variables were measured by validated and standardized self-report inventories. These included screening questionnaires for depression and generalized anxiety (PHQ-4), the short form of the General Procrastination Scale (GPS-K), the Copenhagen Burnout Inventory (CBI), and the Life Satisfaction Questionnaire (FLZ-M) during the interview.
The PHQ-4 [28 (link)] consists of two items reliably assessing the core symptoms of depressed mood and loss of interest plus two screening items of the short form of the GAD-7 (Generalized Anxiety Disorder [GAD]-7 Scale) : “Feeling nervous, anxious or on edge” and “not being able to stop or control worrying”. The frequency of occurrence in the past two weeks was rated from 0 =”not at all”, 1 =”several days”, 2 =”over half the days”, and 3 =”nearly every day”. Answers of the first two items were added into a total score (0 to 6); a score ≥ 3 has a good sensitivity (87 %) and specificity (78 %) for major depression. Cronbach alpha in the present study was = .83. A sum score ≥ 3 (range 0–6) of the other two items indicates generalized anxiety with good sensitivity (86 %) and specificity (83 %), performing well as a screening tool for all anxiety disorders [29 (link)]. The internal consistency in the current study was Cronbach alpha = .77.
Procrastination was assessed by the 9-item short form of the General Procrastination Scale (GPS-K; [30 (link)]). Participants rated how characteristic they considered each behaviour (e.g. “I delay the completion of certain things”) on a 4-point scale (1=”very uncharacteristic” to 4 = “very characteristic”). The scale showed good reliability and validity in a representative German community sample [30 (link)]. The internal consistency was Cronbach alpha = .92.
The Copenhagen Personal Burnout Inventory (CBI; [31 (link)]) is part of the Copenhagen Psychosocial Questionnaire assessing physical and mental exhaustion, independently from work. It assessed the frequency of six items („How often do you feel …“): “tired, physically, emotionally exhausted, unable to go on, weak and prone to illness.” The items were rated on a 5-point scale 1 =”never/almost never”, 2 = “rarely”, 3 = “occasionally”, 4 = “often” to 5 = “always” (COPSOQ; [32 (link)]). The scale was reliable (Cronbach alpha in the present study = .91).
The Questionnaire on Life Satisfaction FLZ^M [33 ] is a multi-dimensional self-report measure of individual life satisfaction covering eight relevant areas of life (friends, leisure time activities/hobbies, general health, income, work/career school, housing/living conditions, family life and partnership/sexuality). Additionally, a sum score of all dimensions was used as an index of global life satisfaction. Respondents rated the present satisfaction with these dimensions on a scale from 1 = “dissatisfied” to 5 = “very satisfied”. As the scale bases conceptually on different domains, the life satisfaction sum-scores indicated only sufficient internal consistency (Cronbach alpha = .70).

The dependent variable in this study was depression, which was set as a dichotomous variable based on the CHARLS questionnaire. The 10-item Center for Epidemiologic Studies Depression Scale (CES-D-10), which is a simplified version of The Center for Epidemiologic Studies Depression Scale, is included in the questionnaire of the CHARLS. Each question was scored on a scale of 0–3 (rarely or not at all = 0, not too much = 1, sometimes or half the time = 2, most of the time = 3). The final score was calculated cumulatively, with a total score of 0–30. When the scores were ≥ 10, the respondent was considered to have depressive symptoms, and below 10, the respondent was considered normal. The depression score also reflected the levels of depression in the sample; therefore, the depression was also examined as a continuous variable in this study. The higher the depression score, the higher the levels of depression (Cronbach’s alpha = 0.805).

Self-rated health^{55 (link)} is measured using a 5-point scale (1 = poor, 2 = fair, 3 = good, 4 = very good and 5 = excellent) in response to the question ‘How would you rate your current health?’. Depressive symptoms [20-item Center for Epidemiologic Studies Depression Scale (CES-D)]⁵⁶ are completed by each participant. Self-rated memory is measured using a 7-point scale in response to the question ‘Overall, how would you rate your memory in terms of the kinds of problems that you have?’. The scores are summarized as 1–3 = major problems, 4 = neutral and 5–7 = no problems.