Mental Health and Targeted Violence
Other recent research has begun to explore the possible relationships between trauma, mental health, and violent extremism.
The types and rates of mental health disorders found in recent studies show that mental health disorders differ significantly from one another and there is no common diagnosis.
Group-Level Studies
When looking at group-level studies, many note single instances of mental health disorders, such as depression (Bakker, 2006), Asperger syndrome, schizophrenia (Knight et al., 2017), ADHD, psychotic disorder, borderline personality disorder and PTSD (Van Leyenhort and Andreas, 2017)
Court-Ordered Expert Opinions
Court-ordered expert opinion on 29 individuals convicted of Jihadist-related crimes (Leygraf, 2014) showed that three individuals had schizophrenic psychosis and two individuals had primary dissocial psychosis. Additionally, police files of 140 Dutch individuals who became foreign fighters found psychotic, narcissistic, attention-deficit/hyperactivity (ADD/HD), schizophrenia, autism spectrum, and post-traumatic stress (PTSD) disorders (Weenick, 2015).
Lone-Actor Samples
Other lone-actor terrorist samples also found a range of mental health problems. A sample of 153 lone-actor terrorists found that 1.3% experienced traumatic brain injury, 0.7% drug dependence, 8.5% schizophrenia, 0.7% schizoaffective disorder, 2.0% delusional disorder, 0.7% psychotic disorder, 7.2% depression, 3.9% bipolar disorder, 1.3% unspecified anxiety disorder, 0.7% dissociative disorder, 1.3% obsessive compulsive disorder (OCD), 3.3% PTSD, 0.7% unspecified sleep disorder, 6.5% unspecified personality disorder, and 3.3% autism spectrum disorder (Corner, Gill, and Mason, 2016). A closed source study of 49 UK lone-actor terrorists found that 12.2% experienced a mood disorder, 10.2% schizophrenia, 4.1% intellectual disabilities, and 2% an assortment of personality disorders. (Gill et al., 2019).
Overall, these are low rates which do not appear to be higher than in what would be found in other at-risk sub-populations or even in general populations.