Better diagnosis could lead to more targeted help for drug use

Effective treatment and care of substance use disorders requires reliable and valid diagnosis. Their diagnosis in mental health services reportedly remains inconsistent despite their prevalence and associated harms. This study examines routine substance use disorder diagnosis across public adult mental health services to identify patterns. Care recorded in the statewide electronic health record of 58,724 adults over 4 years was analysed. Substance use disorder diagnosis, specified and aggregated by substance class and clinical state, was compared across gender, age, substance class and diagnostic groups. Substance use disorder was present in 34.4% of patients. Common specific substance classes were nicotine, cannabinoids, alcohol and stimulants (excluding cocaine). The most common class at 14.1% was multiple and other drug use. Of those with any substance use disorder, 45.3% had multiple and other drug use or other residual use disorders and 21.3% had substance-induced psychosis. People with schizophrenia had higher proportions of substance use disorders than the entire cohort. Substance use disorder diagnostic practice lacks specificity and consistency with diagnostic classification guidance. Disorders requiring combined consideration of aetiology and comorbidity, including 'multiple and other drug use' disorders and substance-induced psychosis, may be over-diagnosed. Nicotine use disorder is likely under-diagnosed. Improving diagnostic specificity is central to effectively treating substance use disorders. Non-specific substance use disorder diagnoses, including 'multiple and other drug' use, should be avoided unless necessary. Specific substances should be named. Consistent use of diagnostic classifications and ongoing diagnostic review are vital for diagnostic clarification and specific treatment.