Brain disease models of psychopathology, such as the popular chemical imbalance explanation of depression, have been widely disseminated in an attempt to reduce the stigma of mental illness. Ironically, such models appear to increase prejudicial attitudes among the general public toward persons with mental disorders. However, little is known about how biochemical causal explanations affect the perceptions of individuals seeking mental health treatment. Ninety undergraduate students participated in a thought experiment in which they were asked to imagine feeling depressed, seeking help from a doctor who diagnosed them with major depressive disorder, and receiving, in counterbalanced order, a chemical imbalance and biopsychosocial explanation for their symptoms. Ratings of each explanation's credibility and perceptions of self-stigma (e.g., blame), prognosis, and treatment expectancies were obtained. Compared to the biopsychosocial model, the chemical imbalance model was associated with signifi antly less self-stigma but also significantly lower credibility, a worse expected prognosis, and the perception that psychosocial interventions would be ineffective. The chemical imbalance explanation appears to reduce blame at the cost of fostering pessimism about recovery and the efficacy of nonbiological treatments. Research is needed on how the chemical imbalance model affects the clinical response of patients receiving mental health treatment.