Background Recent studies suggest an association between sympathies for violent protest and terrorism, and major depression, anxiety, post-traumatic stress disorder and psychiatric disorders in subgroups of radicalised people and in lone-actor terrorists. Aims The aim of this study is to identify and analyse all documented terrorist attacks in the Global Terrorism Database (GTD), where the motive for terrorism is questioned due to suspected mental health issues. Method This study is based on a semi-quantitative, epidemiological analysis of all incidents from 1970 to the first half of 2021, as reported in the GTD. Incidents in which the act of terrorism was questionable because of alleged mental illness were included. Temporal factors, location, target type, attack and weapon type, perpetrator type and number of casualties were collated. Results One hundred and two incidents in the period 1970–2020 and five incidents in 2021 were studied. The majority occurred in the period 2011–2020. The incidents resulted in a total of 99 fatal and 217 non-fatal injuries. Twenty-nine perpetrators died during the attacks. The majority of the attacks occurred in the USA, followed by France and the West Bank and Gaza Strip. Armed assaults were the most frequently identified attack type (67%). In North America, the incidence was as high as 8.2 and 3.4% of the total number of terrorist attacks in the periods 2001–2010 and 2021, respectively. Most of the perpetrators acted as lone actors. Five assailants were detained in a psychiatric facility after the judicial probe, 18 were convicted and 9 had not been sentenced. Conclusions The possible relation between terrorism and mental illness or addiction is a recent phenomenon in the GTD. The prototypical case consists of a lone actor suffering from an assumed mental illness committing an armed assault. Only a minority of perpetrators were unable to stand trial in this series.
Verveckken et al. (Wed,) studied this question.