Does selectively endorsing different approaches to treating mental illness affect lay beliefs about the cause and course of mental illness?

•Promoting particular treatment approaches in clinical communication or public discourse may have ancillary effects on lay beliefs about mental illness.•Lay understandings of the causes and course of mental illness have important implications for help-seeking, treatment engagement and stigma.•Effects on illness beliefs may be an important consideration when making and framing endorsement of a particular treatment. The current paper reports three experimental studies that investigate how selectively emphasising different treatment approaches (biological, psychological or social) for mental health difficulties affects lay beliefs about those illnesses. Online experimental vignettes exposed participants to different treatment narratives for a clinical case of Major Depressive Disorder (Study 1; n=164), Generalized Anxiety Disorder (Study 2; n=173) and Schizophrenia (Study 3, n=170). Measures of causal attributions and illness perceptions assessed effects on beliefs about the causes and course of the illness. Emphasising psychological treatment of Major Depressive Disorder promoted more causal attributions to personal weakness, while endorsing biological treatment weakened confidence in individual control over the course of the illness. For Generalized Anxiety Disorder, stressing social treatment encouraged more causal attributions to personal weakness and lifestyle factors. Causal attributions for Schizophrenia did not shift according to treatment modality, but highlighting biological treatment made the symptoms appear more treatable, while emphasising psychological treatment made the illness seem more personally controllable. As lay understandings of the causes and course of mental illness have implications for help-seeking, treatment engagement and stigma, effects on illness beliefs may be an important consideration when endorsing a particular treatment approach in public discourse or clinical communication.