Prevalence of comorbid mental illness and drug use recorded in general practice : preliminary findings from the general practice research database

Preliminary analysis of a large UK general practice database was conducted in order to determine the prevalence of mentally ill patients in primary care who are also diagnosed with a drug abuse problem and vice versa. The baseline population was 527,000 of whom 1308 patients (prevalence 0.25%) were diagnosed with a drug abuse problem; 59,359 patients suffered a mental illness (11.26%) between 1993 and 1997. Comorbidity was defined by diagnoses of mental illness and drug abuse at any time between 1993 and 1997 (i.e. not necessarily simultaneously): 621 (0.12%) patients were found to be comorbid according to this definition. Neurosis was the most common condition for both mentally ill and drug-abusing patients. Drug abusers were found to have higher rates of psychosis, schizophrenia, paranoia and personality disorders than those with only a mental illness. However, little difference was observed in the prevalence of these conditions between those classed as drug addicts and non-addicts. These findings show that those regarded as non-dependent suffer from mental illness to the same extent as those who are addicted or dependent on drugs. This raises issues regarding service and treatment provision, as emphasis is usually placed on treating the addicted. Future analysis will concentrate on elucidating the time relationships in order to determine possible patterns of causality