No variable left behind: The necessity for multi-variable assessments of insomnia

Insomnia is a multifaceted sleep disorder, with multiple sleep-related and daytime functioning variables being pertinent for its assessment and treatment (American Psychiatric Association, 2013; Sateia, 2014). The use of a singular primary outcome (as is often the case in randomized controlled trials [RCTs] and sometimes the case with clinical treatment), minimizes or undervalues the complex nature of insomnia. The desire to define illness severity and treatment-related change with one number is understandable, although trials with multiple endpoints are more common (US Food and Drug Administration, 2022). The single variable approach, however, risks missing unanticipated effects or that the target therapeutic outcome may co-occur with one or more negative outcomes (e.g., within-night rebound insomnia). In this article, we endeavor to make clear why a multi-variable approach is necessary for insomnia assessment, outlining how different aspects of sleep must be assessed to accurately diagnose, treat, and evaluate treatment outcomes for insomnia.