
This evidence-based resource explores the critical role of medication adherence in behavioral health and the impact of nonadherence on treatment outcomes for conditions such as schizophrenia, bipolar disorder, and major depressive disorder. The guide examines the limitations of traditional adherence assessment methods—including patient self-report, clinician assessment, and pharmacy records—and highlights how definitive drug testing can provide objective insights into medication adherence, substance use, and treatment response. It also offers practical guidance for integrating adherence testing into behavioral health workflows, including the use of oral fluid testing, patient-centered communication strategies, and risk-based monitoring approaches to support informed clinical decision-making, improve patient engagement, and enhance long-term treatment outcomes.