Interaction of chronic diseases and levels of mastery on the course of depression

BACKGROUND: Chronic diseases may negatively interfere with the course of depression. Our aim was to examine whether the association between chronic disease and course of depression is moderated by mastery.

METHOD: N = 1146 persons, aged 18-88, with depressive disorder according to DSM-IV criteria were followed for two years. Outcomes were change in depression severity (change in IDS-SR) (n = 945), chronic course (life chart interview) (n = 971), depression at follow-up (DSM-diagnosis) (n = 971), and time to remission (life chart interview) (n = 799). Predictors were number of chronic somatic diseases and mastery. Regression models (linear, logistic and Cox) were used, adjusted for depression severity, sociodemographics, loneliness, smoking and alcohol use. Next, an interaction term (chronic diseases*mastery) was added to the models.

RESULTS: We only found significant interaction between mastery and chronic diseases (p = 0.02), when outcome was defined as change in depression severity. In analyses, stratified for level of mastery, chronic diseases were significantly associated with chronic course in persons with moderate (B = 1.03; p = 0.03) and high (B = 1.10; p = 0.02) mastery levels. In unstratified analyses, mastery was associated with both chronic course (B = -0.18, p = 0.03) and time to remission (B = 1.03; p < 0.001). Chronic diseases did not reach significance in three outcomes.

CONCLUSION: While impact of chronic diseases on depression trajectories was less consistent than expected, when present, this association was moderated by mastery, suggesting that persons with higher levels of mastery may have difficulties coping with somatic illnesses. In clinical practice, attention to the impact of somatic diseases and coping strategies, in persons with higher levels of mastery, is warranted.