This study determined the prevalence of and factors associated with comorbid major depressive disorder (MDD) in patients with Gilles de la Tourette syndrome (GTS). How a simple self-report instrument, the Beck Depression Inventory (BDI), correlates with clinical assessment of comorbid MDD in this population was assessed. In a continuous sample of 114 adult patients with GTS, assessed clinically using the Diagnostic and Statistical Manual of Mental Disorders-IV criteria, 26 (23%) patients met criteria for MDD; more severe tics as measured with the Yale Global Tic Severity Scale, conduct disorder in childhood or higher age at the time of assessment were associated with MDD. The BDI score had a high negative predictive value for diagnosis of MDD, but a low positive predictive value. Using the BDI as a screening tool for comorbid MDD in patients with GTS is suggested.
