Substance use and re-imprisonment: A longitudinal study of the Norwegian Offender Mental Health and Addiction (NorMA) cohort

Re-imprisonments are common among the substance using prison population. This study investigates re-imprisonment among a cohort of prisoners according to different levels of pre-prison substance use. This was a longitudinal cohort study using baseline data from the NorMA cohort (n=733) merged with data from the Norwegian Prison Registry (follow-up time: 1 January 1992 – 31 December 2019). The NorMA cohort is a representative sample of the prison population at the time of data collection in terms of age, sex, drug use related crime, re-imprisonment and sentence length. Average follow-up was 5 years (SD:1.55). The main exposure was self-reported substance use before imprisonment categorised into three levels of substance use (low-risk, harmful and high-risk), measured at baseline by the Drug Use Disorder Identification Tool (DUDIT) and the Alcohol Use Disorder Identification Tool (AUDIT). The main outcome was re-imprisonments during follow-up. More than half of the NorMA cohort reported high-risk substance use before imprisonment. Over 40 % (n=304) were re-imprisoned after baseline. High-risk substance use was associated to significantly more re-imprisonments (aIRR = 2.11, CI: 1.90-2.34), compared to low-risk substance use. Prior imprisonments, substance use related sentences and more convictions in the baseline imprisonment were also associated with re-imprisonments. Older age, being female, higher education than primary school and occupation before imprisonment were associated with reduced re-imprisonments.

Compared to low-risk use, high-risk substance use is highly prevalent among the prison population and is associated with higher rates of re-imprisonment.

Disclosure of interest statement: The project is financed by the South-Eastern regional Health Authority of Norway.