Background: There is great promise in the use of apps for the treatment of depression. Yet, there is uncertainty as to the alignment of publicly available depression apps with clinical guidance, their treatment fidelity and evidence–base, and their overall safety.

Objectives: This study built on previous analyses and reviews to explore treatment and safety issues of publicly available apps for depression.

Methods: We conducted a content analysis of apps for depression in the two main UK apps stores (Google Play and Apple iTunes). App store listings were analyzed for intervention content, treatment fidelity, and fit with the National Institute for Health and Care Excellence (NICE) guidelines for the treatment of depression in adults.

Results: A total of 353 apps for depression were included in the review. App descriptions reported use of 20 treatment approaches and 37 treatment strategies. Many apps used transdiagnostic (155/353, 43.9%) and multitheoretical interventions to treat multiple disorders including depression. While many interventions appeared to be evidence–informed, there were issues with treatment fidelity, research evidence, and fit with clinical guidelines. None of the apps aligned with NICE guidelines for depression.

Conclusions: App developers have adopted many evidence–informed treatments in their interventions, but more work is needed to improve the clinical validity, treatment fidelity, and safety of apps. We urge developers to consult relevant guidelines and standards, and to engage in reflective questioning on treatment and safety to address these issues and to improve treatment content and intervention design.