OBJECTIVES: Insomnia is frequently associated with generalized anxiety disorder (GAD) and affects the patient's day to day life. The Sleep Impact Scale (SIS) was developed to assess the impact of insomnia; however it has not been used in GAD. Therefore, a study was conducted to validate the SIS and evaluate the impact of zolpidem tartrate extended-release on insomnia in GAD. METHODS: Validation and efficacy data of the SIS were collected alongside a randomized, placebo-controlled trial of escitalopram+placebo or zolpidem tartrate extended-release in adults with insomnia associated with GAD. The validation consisted of evaluation of the validity and reliability, the responsiveness and the MID of the SIS domains to ensure the questionnaire was acceptable in a GAD population. The efficacy analysis was performed on the ITT population, consisting of general linear models to evaluate changes from baseline at each timepoint, with study endpoint as the primary change score analysis. Longitudinal analyses were also performed to evaluate the effects of treatment through time using repeated measures ANCOVA. RESULTS: The SIS was found to meet psychometric standards for a valid questionnaire in a GAD population. The efficacy analysis found four domains (Daily Activities, Emotional Impact, Energy/Fatigue and Satisfaction with Sleep) consistently demonstrated significantly greater improvements in the zolpidem tartrate extended-release group at each timepoint. A quick onset of treatment effect was evident in all domains of the SIS by Week 2, with all domains statistically significantly demonstrating greater improvement than placebo. Longitudinal analyses found all SIS domains to be statistically significantly superior to placebo. CONCLUSION: The SIS adequately meets the criteria for a validated measure to be used in GAD. The SIS was responsive to treatment effects in this clinical trial and able to demonstrate improvements in patient reported outcomes, favoring zolpidem tartrate extended-release.