The incremental burden of pain in patients with depression: results of a Japanese survey

Major depressive disorder (MDD) is a chronic mental illness which affects an estimated 3% of the Japanese population. Many patients with MDD report painful physical symptoms, and research outside of Japan suggests such patients may represent a subtype of depression which is more severe and difficult to treat. There is no evidence available about the characteristics or incremental burden of these patients in Japan. The objective of this study was to quantify the incremental burden of physical pain among individuals in Japan diagnosed with depression.

Data for individuals age 18 and older who reported a physician diagnosis of depression were obtained from the Japan National Health and Wellness Survey (NHWS). Respondents who also reported physical pain were matched to respondents who did not report pain using propensity scores and compared using bivariate statistics. Measures included Patient Health Questionnaire (PHQ-9) for depression severity, Medical Outcomes Study 12-Item Short Form Survey Instrument (SF-12v2) for health-related quality of life, the Work Productivity and Activity Impairment (WPAI) for work and activity impairment, and 6-month report of health care use.

Individuals with depression who reported physical pain had higher PHQ-9 depression scores (14.3 vs. 11.1, p<0.001), lower health-related quality of life (Mental Component Summary score [MCS] 29.1 vs. 32.0, p<0.01; Physical Component Summary score [PCS] 43.0 vs. 47.2, p<0.001; health utility [SF-6D] 0.567 vs. 0.613, p<0.001), more presenteeism (46.3% vs. 36.8%, p<0.01), more overall work impairment (51.4% vs. 42.3%, p<0.01), more activity impairment (55.4% vs. 43.9%, p<0.001), and reported using more health care provider visits in the prior 6 months (17.7 vs. 12.8, p<0.01) as well as hospitalizations (1.7 vs. 0.8, p<0.05) relative to propensity-score matched controls without pain. Absenteeism (13.1% vs. 11.4%, p=0.51) and emergency room visits (0.31 vs. 0.35, p=0.76) were not significantly different between the two matched groups.

Individuals whose depression is accompanied by physical pain have a higher burden of illness than those whose depression does not include physical pain. Clinicians should take the presence of pain into account and consider treating both the physical and emotional symptoms of these patients.