Insomnia and depression: risk factors for development of depression in male Japanese workers during 2011-2013.

OBJECTIVES

This 3-year cohort study was conducted to investigate the relation between insomnia and development of depression in male workers, and to clarify the association between the severity of insomnia and the onset of depression.

METHODS

Self-administered questionnaire surveys on depression and insomnia were conducted on male workers for 3 years. Depression was assessed with the Center for Epidemiologic Studies Depression Scale (CES-D), and insomnia was examined using the Athens Insomnia Scale (AIS). The analysis was done with 840 men who had no depression at baseline.

RESULTS

Depression symptoms were newly found in 113 men during this study. Cox regression analyses showed that people with insomnia (AIS score of ≥ 1) at baseline had about a 7 times greater risk for onset of depression. Furthermore, compared with those with AIS score of 0 (no insomnia), people with AIS score of 1-3 had a 5.2-fold greater risk of depression and those with a score of 4 or higher indicated about tenfold greater risk.

CONCLUSIONS

A new finding was that the risk for onset of depression increased with the severity of insomnia.