Introduction

There has been a growing and justified interest in co-morbid severe mental illness and substance abuse over recent years, due to its high prevalence and significant impact on clinical and social problems, as well as the heavy burden laid on the health services. The annual health and social costs of misuse of alcohol and illegal substances in England and Wales are each estimated to be nearly £20 billion amongst people aged under 45 (Williams et al. 2005). The great majority of such patients are admitted to Psychiatric Intensive Care Unit (PICU) settings and their management can cause considerable difficulties, especially where there are no adequate evidence-based treatment models designed for inpatients.

The interaction between a psychotic illness and the use of substances is complex and is known to have major detrimental effects on the course of the illness, risk of violence, outcome, physical health complications and even possibly aetiology. In this chapter, these complex interactions will be examined and some management strategies will be discussed.

As mentioned in Chapter 10 on complex needs patients, substance use is one of the main characteristics of this group. Even though most of the studies in this area originate from the USA, the prevalance of substance abuse amongst the severely mentally ill is also known to be high in the UK where the estimated prevalence ranges between 20% and 60% (Miles et al. 2003). In PICU settings the average prevalence can be as high as 85% percent (Isaac et al. 2005).