Background: The aim of the present study was to investigate the effect of job stress on depressive symptoms and whether optimism moderates this relationship longitudinally. Data were used from 2002 until 2014 (wave 2 to 5) of the German Ageing Survey. The sample consists of community-dwelling individuals living in Germany aged from 40 to 95 years (7,086 observations in fixed effects regression analysis). Methods: A self-report questionnaire was used to measure depressive symptoms (Center for Epidemiologic Studies Depression Scale), job stress (scale 1 to 5) and optimism (Optimism Scale of Brandtstaedter & Wentura). Results: Adjusting for potential confounders, fixed effects regression analysis revealed that an increase in job stress was associated with an increase in depressive symptoms, whereas an increase in optimism was associated with a decrease in depressive symptoms. Optimism significantly moderated the relation between job stress and depressive symptoms. Limitations: The possibility of a small sample selection bias cannot be dismissed. Conclusions: The present study highlights the moderating role of optimism in the relation between job stress and depressive symptoms longitudinally. Thus, efforts to increase optimism in individuals might be beneficial in reducing depressive symptoms among individuals with high job stress.

INTRODUCTION

Stress, and in particular job stress, is a psychological issue and a widespread phenomenon caused by work characteristics as well as personal characteristics which leads to adverse health outcomes (Shields, 2006, Iacovides et al., 2003). Stress outcomes like fatigue, heart disease, depression, diabetes and burnout were discussed in previous literature (Cohen and Herbert, 1996, Iacovides et al., 2003, Melchior et al., 2007). Special emphasis is put on depressive disorders because estimations showed that over the course of one year about 8.9% of the working population aged 15 to 65 in Germany fulfill all criteria for a depressive disorder and up to 26.7% experience depressive symptoms (Wittchen and Jacobi, 2006). Health care costs in Europe for depression add up to 118 billion Euros per year (Sobocki et al., 2006). Society, economy and the affected individual have to master an excessive burden caused by depressive disorders resulting from job stress (Shields, 2006). Consequently, economy is weakened by lost productivity in the workplace (Tennant, 2001). Numerous studies have been conducted to examine the relation between stress at workplace and depressive symptoms. Strong evidence showed that job stress is positively correlated with depressive symptoms (Shields, 2006, Iacovides et al., 2003, Dragano et al., 2008, Clays et al., 2007, Kawakami et al., 1992, Lin et al., 2010). Moreover, employees‟ stress management is dominated by coping mechanisms which enhance their mental health. According to Lazarus (1993), mental toughness, personality characteristics, self-efficacy, optimism and educational background have a bearing on an individuals‟ coping behavior. Furthermore, it has been shown that optimism has a positive impact on individual‟s stress-coping ability (Schou and Ekeberg, 2005, Steginga and Occhipinti, 2006). Following, studies have revealed that an increase in optimism lead to a decrease in depressive symptoms (Achat et al., 2000, Symister and Friend, 2003). Concerning optimism as a moderator, a cross-sectional study of Banerjee (2012) investigated the association of dispositional optimism on the stress-depression relationship. A survey method was used and filled in by 94 employees working in a private Indian university. Analysis was conducted with 94 participants (with a mean age of 32.9 years and 79% male participants). Higher psychological stress was associated with a higher depression level, whereas higher dispositional optimism was associated with a lower level of depression. Optimism significantly moderated the relationship between job stress and perceived depression.