Background: Suicide methods chosen by victims are particularly critical in suicide risk
research. To differentiate suicide deaths, it is usual to categorize them as violent and nonviolent
depending on the detrimental method chosen by the victims. Caustic ingestion, for example, is
traditionally considered as a nonviolent suicide method. It results in severe consequences for
the human body and it is associated with high levels of lethality. Methods: In this study, we
retrospectively analyzed suicides that occurred between 1993 and 2021 in Milan (Italy) and that
underwent autopsy. We compared a sample of 40 victims that ingested caustic substances with a
sample of 460 victims of other chemical ingestion, and a sample of 3962 victims from violent suicide.
Univariate analyses and univariate logistic regression models were performed. Suicides from caustic
poisoning were significantly older, had a higher mean number of diseases and were more affected
by psychiatric diseases compared to other chemical ingestion victims. By contrast, caustic suicides,
compared to violent suicides, had a more balanced gender ratio, a higher mean number of diseases,
were more affected by psychiatric diseases, had a higher rate of complex suicides (more than one
modality), and had victims who died more frequently inside instead of outside. In logistic regression
models, age was the only feature differentiating caustic from other chemical ingestion suicides while
the features differentiating caustic from violent suicides were gender, mean number of diseases and
suicide place. Conclusions: Suicides by caustic ingestion showed substantial differences compared to
violent suicides, with a higher severe profile. However, some differences were reported comparing
caustic ingestion to other chemical ingestion as well. Thus, we argue whether it is more appropriate
to differentiate the suicidal ingestion of caustics from both violent and nonviolent suicide methods
