Background: Depression has a high point and life time prevalence and is a major cause of reduced work ability and long-term sickness absence (LTSA). Less is known of the extent to which non-clinical depressive symptoms are related to the risk of LTSA. The aim of this study was to investigate how non-clinical and clinical depressive symptoms are prospectively associated to subsequent LTSA.
Methods: In a cohort study of 6985 femaleemployees fromthe Danish eldercare sector depressive symptoms were measured by the Major Depression Inventory (MDI) and scores (0–50) were divided into groups of 0–4, 5–9, 10–14, 15–19,=20 points and clinical depression. Datawas linked to a national register with information on LTSA (=3 weeks). Hazard ratios (HR) for LTSA during a
1-year follow-up were calculated by Cox's proportional hazards model.
Results: Compared to the reference group (0–4) the HR was stronger for each subsequent group:
MDI scores of 5–9: HR=1.07 (95% CI: 0.93–1.24); 10–14: 1.38 (1.15–1.66); 15–19: 1.54 (1.20–1.98); =20: 1.96 (1.45–2.64); clinical depression: 2.32 (1.59–3.38); after adjustment for previous LTSA, age, family status, smoking, leisure time physical activity, BMI, and occupational group.
Limitations: Missing information on the cause of sickness absence and prevalent somatic illness.
Conclusion: A clear dose–response relationship exists between increasing depressive symptoms and risk of LTSA. The adverse effect of non-clinical depressive symptoms on LTSA already manifests itself at relatively low scores. Clinical relevance: this study illustrates the valuable information of considering the whole continuum of depressive symptoms.