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Background and Objectives: To characterize the impact of pregabalin on sleep in patients with generalized anxiety disorder (GAD) and to determine whether the impact is a direct or an indirect effect, mediated through the reduction of anxiety symptoms. Methods: A post-hoc analysis of data from a randomized, double-blind, placebo- and active-controlled study in patients with GAD was conducted. Patients received pregabalin 300 mg/day, venlafaxine XR 75 mg/day or placebo for a week, followed by pregabalin 300-600 mg/day, venlafaxine XR 75-225 mg/day, or placebo for 7 weeks. Treatment effect on sleep was evaluated using the Medical Outcomes Study Sleep Scale. Anxiety symptoms were assessed with the Hamilton Anxiety Rating Scale. A mediation model was used to estimate separately for both treatment arms the direct and indirect treatment effects on sleep disturbance. Results: Compared with placebo (n = 128), treatment with pregabalin (n = 121) significantly reduced scores on the sleep disturbance subscale and Sleep Problems Index II at both week 4 and week 8, and the sleep adequacy subscale at week 8. Venlafaxine XR (n = 125) had no significant effect on these measures. The mediation model indicated that 53% of the total pregabalin effect on sleep disturbance was direct (p < 0.01) and 47% indirect, mediated through anxiety symptoms (p < 0.05). Conclusions: Pregabalin decreased sleep disturbance in patients with GAD both directly, and indirectly by reducing anxiety symptoms. Given the drug specificity of the results, this study provides evidence of an additional important pathway of action for pregabalin and its efficacy in GAD.
