Characteristics of Individuals With Insomnia Who Seek Treatment in a Clinical Setting Versus Those Who Volunteer for a Randomized Controlled Trial

The generalizability of outcome data derived from insomnia clinical trials is based largely on the extent to which research volunteers resemble clinical patients. This study compared sociodemographic, sleep, psychological, and medical characteristics of individuals who volunteered for an insomnia treatment study (n = 120) to patients who sought treatment in a clinical setting (n = 106). The samples did not differ on most sleep and medical variables, but clinical patients had a higher prevalence of mood disorders, greater anxiety and depression symptoms, and higher perceived insomnia severity. Differences on psychological variables were accentuated by the research selection process. It is suggested to minimize exclusion based on psychological comorbidity in order to enhance ecological validity of randomized controlled trials of insomnia treatments.