A psychologist is able to interview and has assessment tools to evaluate a person for mental illness. The diagnosis is based on the person’s report of symptoms including any social or functional problems caused by the symptoms as well as observation of the person’s attitudes and behaviour.

The person’s symptoms and degree of disability point to a diagnosis of a specific disorder. The standard manual used for the diagnosis of recognised mental illness is the Diagnostic and Statistical Manual of Mental Disorders Fifth Edition (DSM-5).

Appropriate referrals are made to psychiatrists with whom a psychologist can work conjointly.