Primary and secondary substance misusers: do they differ in substance-induced and substance-independent mental disorders?

AIMS This study evaluated the primary/secondary distinction among substance misusers according to comorbid mental disorders. METHODS A consecutive sample (n = 287) of DSM-IV substance dependents from public treatment facilities in two counties in Norway were assessed by the Composite International Diagnostic Interview. According to the debut of the first independent mental disorder, patients were divided into primary substance use disorder (SUD) (17%), secondary SUD (76%) and SUD in the same year as the first mental disorder (7%). RESULTS A lifetime substance-independent mental disorder was found in 90%. Forty-two per cent had a combination of substance-independent and substance-induced mental disorders. Five per cent had substance-induced mental disorders only. Primary SUD patients comprised less women, and a lower number of substance-independent mental disorders. Secondary SUD patients had more major depression, phobic disorders and obsessive-compulsive disorder. There were no differences between primary SUD and secondary SUD regarding the number of substance-induced disorders or the pattern of substance misuse. CONCLUSIONS Clinical differences between primary and secondary SUD were small and do not support the distinction.