Background Fatal drowning is one of the leading causes of unintentional injury mortality worldwide and a persistent public health concern in Greece. While several pathologic and sociodemographic contributing factors have been previously identified, these have not been extensively investigated in conjunction with the effects of psychoactive substances.

Methods A retrospective case–control study of drowning deaths was conducted in the Greek regions of Northern Greece and Thessaly during a 10-year period. A regression model was constructed examining differences in detected substances, autopsy findings and sociodemographic characteristics between 240 victims of unintentional fatal submersion and 480 victims of other causes of sudden or violent death.

Results The majority of victims were males (69.4%) and foreign nationality was associated with increased odds of drowning. Cardiomegaly and coronary bypass grafts were significantly more likely to have been recorded among drowning victims, while the frequency of other circulatory system disorders was also elevated. Several of these findings were potential arrhythmogenic substrates which could adversely interact with the diving reflex. Selective serotonin reuptake inhibitors (SSRIs) were the most commonly detected pharmacological group (9.0%), and along with tramadol, there was an increased likelihood of exposure to them. These drugs have been previously associated with QT prolongation and other adverse effects which may contribute to fatal outcomes in a seawater environment. In contrast, there was a decreased risk of exposure to dependence-inducing drugs and paracetamol.

Conclusions Male sex, older age, foreign nationality and cardiovascular disease predisposed individuals to an elevated risk of fatal submersion. SSRI antidepressants and tramadol may contribute to this outcome.