This article argues that psychiatric diagnoses are not valid or useful. The use of psychiatric diagnosis increases stigma, does not aid treatment decisions, is associated with worsening long-term prognosis for mental health problems, and imposes Western beliefs about mental distress on other cultures. This article reviews the evidence base focusing in particular on empirical findings in relation to the topics of: aetiology, validity, reliability, treatment and outcome, prognosis, colonialism, and cultural and public policy impact. This evidence points toward diagnostic based frameworks for understanding and intervening in mental health difficulties being unable to either improve our scientific knowledge or improve outcomes in clinical practice and suggests that we need to move away from reliance on diagnostic based approaches for organising research and service delivery. Alternative evidence-based models for organising effective mental health care are available. Therefore formal psychiatric diagnostic systems such as the mental health section of the International Classification of Diseases Tenth Edition (ICD-10) and Diagnostic Statistical Manual Fifth Edition (DSM 5) should be abolished.