Bidirectional relationship between methamphetamine use and positive psychotic symptoms in regular methamphetamine users: Evidence from a prospective cohort study

Background: Methamphetamine (MA) has been consistently associated with positive psychotic symptoms, but little is known about whether the reverse also occurs. Aims: This study determined whether the relationship between MA use and positive psychotic symptoms is bidirectional over 12 months. The impact of lifetime psychotic disorders and MA dependence on these relationships was also examined. Method: 201 regular (at least monthly) primary MA users were recruited from free needle syringe programs in three Australian cities. Data on the frequency of MA and other drug use (Timeline Followback) and the severity of positive psychotic symptoms (Brief Psychiatric Rating Scale) in the past 2 weeks were collected in 12 contiguous monthly face-to-face interviews (mean of 9.14/11 (SD=3.16) follow ups completed). Diagnoses were derived using the Psychiatric Research Interview for DSM-IV Substance and Mental Disorders.