Residual symptoms and functioning in depression, does the type of residual symptom matter? A post-hoc analysis

BACKGROUND: The degrees to which residual symptoms in major depressive disorder (MDD) adversely affect patient functioning is not known. This post-hoc analysis explored the association between different residual symptoms and patient functioning. METHODS: Patients with MDD who responded (≥50% on the 17-item Hamilton Rating Scale for Depression; HAMD-17) after 3 months of treatment (624/930) were included. Residual core mood-symptoms (HAMD-17 core symptom subscale ≥1), residual insomnia-symptoms (HAMD-17 sleep subscale ≥1), residual anxiety-symptoms (HAMD-17-anxiety subscale ≥1), residual somatic-symptoms (HAMD-17 Item 13 ≥1), pain (Visual Analogue Scale ≥30), and functioning were assessed after 3 months treatment. A stepwise logistic regression model with normal functioning (Social and Occupational Functioning Assessment Scale ≥80) as the dependent variable was used. RESULTS: After 3 months, 59.5% of patients (371/624) achieved normal functioning and 66.0% (412/624) were in remission. Residual symptom prevalence was: core mood symptoms 72%; insomnia 63%; anxiety 78%; and somatic symptoms 41%. Pain reported in 18%. Factors associated with normal functioning were absence of core mood symptoms (odds ratio OR 8.7; 95% confidence interval CI, 4.6-16.7), absence of insomnia symptoms (OR 1.8; 95% CI, 1.2-2.7), episode length (4-24 weeks vs. ≥24 weeks OR 2.0; 95% CI, 1.1-3.6) and better baseline functioning (OR 1.0; 95% CI, 1.0-1.1). A significant interaction between residual anxiety symptoms and pain was found (p = 0.0080). CONCLUSIONS: Different residual symptoms are associated to different degrees with patient functioning. To achieve normal functioning, specific residual symptoms domains might be targeted for treatment.