Impact of Axis I comorbidity interaction on duloxetine outcome in major depression

Objective: In the last decades a substantial advance in the understanding of the influence of different variables on response to antidepressants has been achieved. However, little effort has been paid so far to investigating how such factors interact with each other to predict clinical improvement. Accordingly, the present study aimed to explore whether and how concurrent or lifetime psychiatric comorbidities could influence clinical outcome in a sample of patients with major depressive disorder (MDD) treated with duloxetine. Method: One-hundred-one outpatients suffering from MDD were treated with duloxetine. They were assessed at baseline and at weeks 2, 4 and 8 by means of the 21 item Hamilton rating scale for depression (HAMD). Concurrent and lifetime comorbidities with other axis I psychiatric disorders were recorded by MINI-international Neuropsychiatric interview (M.I.N.I.) and the impact of the interactions of such comorbidities on clinical outcome was assessed. Results: We observed a significant effect of the interactions between current obsessive compulsive disorder (OCD) and lifetime generalized anxiety disorder (GAD), as well as between lifetime panic disorder (PD) and lifetime GAD, current premenstrual dysphoric disorder (PDD) and current or lifetime PD, and current PDD and lifetime GAD on improvements of HAM-D during the study period. Conclusions: Our results provide preliminary evidence to suggest that 5 different clinical variables including current OCD X lifetime PD or GAD, as well as current PDD X lifetime PD or GAD could interact with each other to predict clinical improvement in MDD patients treated with duloxetine. However, on account of several limitations, including the focus on a limited number of predictors and the relatively small sample size of our study, further research is needed to draw more definitive conclusions.