Work productivity loss with depression, diagnosed and undiagnosed, among workers in an Internet-based survey conducted in Japan.

Objective: The aim of this study was to investigate whether depression severity was associated with work impairments, regardless of the diagnosis.

Methods: We conducted a cross-sectional study among 17,820 Japanese workers using an Internet-based survey. Work impairments were assessed using the Work Productivity and Activity Impairment questionnaire. Participants were grouped according to whether they had a past-year diagnosis of depression by physicians and current depression severity assessed with the Patient Health Questionnaire-9.

Results: Among the undiagnosed, high severity respondents had greater overall work impairment than low severity respondents (33.3% vs 14.8%). Significant interactions between diagnosis and severity indicated greater impairments among undiagnosed than among diagnosed respondents (except on absenteeism).

Conclusions: Depression severity was associated with work productivity loss, even among the undiagnosed, suggesting a need for early detection, referral, and treatment of depression in the workplace.