To the Editor: There has been much public discussion recently about comorbidity between substance misuse and psychiatric disorders.1,2 Drug and alcohol misuse can precipitate, exacerbate and prolong psychiatric disorders, and is often accompanied by a range of social problems. Here we report on the prevalence of substance misuse in an unselected group of patients admitted to the 20-bed acute psychiatric facility at Lyell McEwin Health Service, situated in an underprivileged region of northern Adelaide. The facility has five closed beds and 15 open beds.

In October 2005, 45 patients (23 men, 22 women; mean age, 39 years) were admitted to the unit, of whom 28 (62%) were detained involuntarily. Semi-structured interviews, clinical history taking and collateral information gathering revealed that 27 patients (60%) had a comorbid substance misuse disorder. The most common substance misused was cannabis (20 patients [44%]), followed by alcohol (16 patients [36%]), amphetamines (15 patients [33%]), opiates (6 patients [13%]) and benzodiazepines (5 patients [11%]). Misuse of more than one substance was common — for example, all 15 patients diagnosed with amphetamine misuse also misused cannabis. Patients who misused cannabis were younger (mean age, 33 years) than those who did not (mean age, 44 years) (t43 = 0.23; P = 0.023) and were more likely to be male (61% of male patients misused cannabis compared with 27% of female patients; χ2 = 5.14; P = 0.036). Of 19 patients with psychotic disorders, 11 misused cannabis.

These results indicate high rates of substance misuse in patients admitted to a psychiatric facility. Cannabis misuse by young men is a particular concern. It is apparent that more than half of inpatients with acute psychiatric conditions could benefit from interventions to address their substance misuse.

The extent of cooperation between drug and alcohol services and mental health services varies between different localities and between the private and public sectors. In states such as South Australia, where there is a historical separation between drug and alcohol services and mental health services, the treatment of these disorders is regarded as outside the role of mental health services. Patients considered to have a primary problem with substance misuse are treated by specialised drug and alcohol services. This service divide does not reflect clinical reality. Patients with comorbidity can “fall through the cracks”, each service regarding them as someone else’s responsibility.

Postgraduate training in psychiatry includes both academic input and the submission of case logs describing 10 patients with addiction disorders, but this aspect of training may need to be expanded in response to changes in the pattern of disorders in the patient population. Mental health clinicians, along with general practitioners and doctors working in settings such as emergency departments, will increasingly need to be highly skilled in diagnosing and managing comorbid drug and alcohol and psychiatric disorders.