Adults and young people with coexisting severe mental illness and substance misuse have some of the worst health, wellbeing and social outcomes (see the Social Care Institute for Excellence's briefing on the relationship between dual diagnosis: substance misuse and dealing with mental health issues).

It is not clear how many people in the UK have a coexisting severe mental illness and misuse substances, partly because some people in this group do not use services or get relevant care or treatment.

The Department of Health's Refocusing the Care Programme Approach identifies people with coexisting severe mental illness and substance misuse as one of the groups in need of an enhanced Care Programme Approach. That is because they are not being identified consistently and services are sometimes failing to provide the support they need. The policy highlights the need for a whole systems approach to their care, involving a range of services and organisations working together. This guideline aims to address this need.

Groups covered in this guideline include: young people (aged 14 to 25) and adults who have been diagnosed as having a severe mental illness and who misuse substances and who live in the community. The age cut-off for young people has been set at 14 to reflect the small numbers affected below this age – and the fact that many early intervention services usually start at age 14.

In this guideline, severe mental illness includes a clinical diagnosis of:

  • schizophrenia, schizotypal and delusional disorders or

  • bipolar affective disorder or

  • severe depressive episodes with or without psychotic episodes.

Substance misuse refers to the use of legal or illicit drugs, including alcohol and medicine, in a way that causes mental or physical damage.

  • National Institute for Health and Care Excellence (NICE)