Introduction Major depressive disorder (MDD) is the leading cause of disability worldwide and its impact on patients' functioning exceeds that of chronic medical conditions. Previous studies reported that severity of depression and disability show synchrony of change. However, there are patients with severe depressive symptoms who function rather well, suggesting that certain characteristics influence the association between depression severity and disability. Advancing previous research which focused mostly on the effect of illness characteristics, this current study aimed to identify additional personal and environmental characteristics that affect the synchrony of change among depressed patients. We assessed (1) whether the course of disability is dependent on the course of depressive symptom severity and (2) whether this synchrony of change is moderated by illness, personal, and environmental characteristics.

Methods Depression severity and disability of 507 participants with a diagnosis of MDD at baseline were measured three times in 2 years. Illness, personal, and environmental characteristics were measured at baseline. For the statistical analysis, Linear Mixed Models were used.

Results Preliminary results indicated that change in disability was synchronous to change in depressive symptoms. Furthermore, high agreeableness and high work stress led to impaired functioning despite mild depressive symptoms whereas higher age and conscientiousness led to better functioning despite severe depressive symptoms.

Conclusions This study indicates synchrony of change between depression severity and disability. However, some personal and environmental characteristics cause an exemption to this and may thus be useful to consider during treatment of depression in order to decrease disability among MDD patients.