Background Alcohol is a well-known risk factor in unintentional drownings. While psychotropic drugs may also cause psychomotor impairment and affect cognition, no detailed studies have focused on their association with drowning. Finland provides extensive post-mortem toxicological data for studies on drowning due to its high medico-legal autopsy rates.

Methods Drowning cases, 2000 through 2009, for which post-mortem toxicological analysis was performed, were selected from the database of Toxicological laboratory, Department of Forensic Medicine, University of Helsinki, using the ICD-10 nature of injury code T75.1. The data were narrowed down to unintentional drowning, using the ICD-10 external injury codes V90, V92 and W65–74. For each drowning case, the blood alcohol concentration (BAC) and the concentrations of other drugs were recorded. The contribution of psychotropic drugs to drowning was evaluated based on their blood concentration by mean of a 6-grade scale.

Results Among victims ≥ 15 years old, there were 1697 unintentional drownings. 303 (17.8%) were boating-related and 1394 (82.2%) non-boating-related. 65.0% of boating-related and 61.8% of non-boating-related victims were alcohol-positive (= BAC ≥ 0.5 ‰). The male to female ratio in alcohol-positive drownings was 7.3. At least one psychotropic drug was found in 453 (26.7%) drowning cases, with some victims having up to 7 different drugs. Overall 70 different psychotropic drugs were detected. 134 (7.9%) cases were both alcohol-negative and psychotropic drug -positive, of them 59 (3.5%) were graded 4 to 6, indicating possible to very probable contribution to drowning.

Conclusions Psychotropic drugs alone or in association with alcohol may be an overlooked risk factor to drowning due to their effects on psychomotor function and cognition. Future studies should also address other mechanisms, for instance drug-induced long QT-syndrome, by which drugs may contribute to drowning.