The contribution of imprisonment and release to fatal overdose among a cohort of Norwegian drug abusers

This study was designed to supplement knowledge of three aspects of fatal overdose and imprisonment. Our aims were to investigate whether drug abusers arc subject to a higher-than-usual risk of fatal overdose immediately after release from prison, to assess the length of the high-risk period and to investigate the net effect of imprisonment - the pooled effect of both imprisonment and release - on overdose death. The analyses were conducted on the basis of data from a cohort of 338 imprisoned Norwegian drug abusers. Cox regression models were applied including the explanatory time-dependent covariate for imprisonment and the post-release period. We find that the risk of death from overdose during the 2 weeks after release from prison was 10 times higher, and during the 3-week period six times higher, than during other time spent outside prison. An elevated risk was also indicated for the fourth week. Taking into account findings in the literature, the period of elevated risk should be considered to last up to 4 weeks. When the risk period analysed includes both time spent in prison and the post-release period, the risk of fatal overdose is not found to differ from other periods outside prison.