This guideline offers best practice advice on the assessment and management of people with psychosis and coexisting substance misuse.

Psychosis is a condition that affects a person’s mental state, including their thoughts, mood and behaviour. The symptoms of psychosis are:
• hallucinations – hearing voices and sometimes seeing things that are not really there
• delusions – having fixed beliefs that are false but which the person believes in completely.

Substance misuse is a broad term encompassing, in this guideline, the harmful use of any psychotropic substance, including alcohol and either legal or illicit drugs. Use of such substances is harmful when it has a negative effect on a person’s life, including their physical and mental health, relationships, work, education and finances or leads to offending behaviour.