A novel benzodiazepine detected after death is not automatically the drug that caused the death. A Victorian study of 140 overdose deaths used a narrower inclusion rule: forensic medical experts had determined that at least one novel benzodiazepine contributed to the fatal outcome. Its changing drug counts describe that selected group, rather than every positive autopsy test or the risk per person using each substance.
How the registry selected the deaths
Schumann, Syrjanen and Dwyer examined the Victorian Overdose Deaths Register for 1 January 2009 through 31 December 2023. Trained coders reviewed deaths reported to the Coroners Court of Victoria. Registry inclusion required forensic medical evidence, including toxicology and autopsy, that acute toxic effects of one or more drugs played a contributory role.
The researchers extracted the contributing novel benzodiazepines and dates of death. They identified 140 deaths: 109 males and 31 females, aged 17–61 years. The earliest was in 2015, with only two before 2019. Annual counts were 10 in 2019, 28 in 2020, 26 in 2021, 40 in 2022 and 34 in 2023.
These were historical Victorian findings. The paper did not supply the number of people exposed to each drug, a living comparison group, or an all-deaths toxicology denominator. Consequently, the counts cannot rank individual drugs by fatal risk.
One death could contribute to several drug counts
Seventy-seven deaths, or 55%, involved one contributing novel benzodiazepine; 63, or 45%, involved multiple novel benzodiazepines. Within the latter group, 48 involved two, seven involved three, four involved four and four involved five.
The most frequently contributing compounds were etizolam in 60 deaths, bromazolam in 39, clonazolam in 34, flualprazolam in 33 and clobromazolam in 21. These overlapping counts must not be added as if they represented different people. A death with two contributing compounds appeared on both corresponding lines in the chronological figure.
The paper also contains an unresolved inconsistency: one results statement says all 140 deaths had a contributing drug outside the novel-benzodiazepine group, while another says 139. That prevents a definitive exact total for this feature from the main report. Either statement makes mixed-drug contribution central to interpretation; neither supports describing the series as 140 isolated benzodiazepine poisonings.
What the temporal clusters showed
The authors visually identified eight groupings, including subgroups. Examples included 39 etizolam-involved deaths from January 2019 through March 2021, 22 flualprazolam-involved deaths from April 2021 through April 2022, and 21 bromazolam-involved deaths from April through December 2023.
Some groupings overlapped in time and drug composition. They were not mutually exclusive categories to sum into a new death total. The investigators expressly acknowledged subjective judgment in choosing the groups; they did not present a formal statistical change-point analysis.
The proposed explanation was a changing unregulated drug supply. That is a hypothesis consistent with the pattern, not direct measurement of the composition of products consumed in every death. The study did not establish an identical national market pattern or show that two co-contributing drugs necessarily came from the same tablet.
What the report cannot tell an individual case reviewer
This registry analysis did not provide one uniform specimen collection site, death-to-collection interval, preservation protocol, concentration dataset or analyte-specific analytical limit. It therefore cannot supply a concentration threshold for fatality or separate antemortem exposure from postmortem concentration change.
Its practical lesson is to preserve the original classification: detection, expert-assessed contribution and a sole causal agent are different claims. The same distinction matters when a single “main intoxicant” category compresses a mixed-drug death. For an individual investigation, the laboratory finding must remain attached to the specimen, analytical evidence, autopsy and circumstances that supported the causal assessment.
Primary source
Schumann JL, Syrjanen R, Dwyer JA. Changes over time in novel benzodiazepines contributing to fatal overdoses in Victoria, Australia. Drug and Alcohol Review. 2025;44:1285–1289. doi:10.1111/dar.14054.
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