Through the media we are often made aware of the mental health of individuals who have engaged in high profile acts of either mass violence or inexplicable acts of violence toward others (
1,
2). Mental disorders such as schizophrenia and mood disorders are often cited as increasing the risk of unlawful behavior, although it is also recognized that this increased risk is modest (
3,
4). More recent studies have also investigated mental disorders among people who have engaged in violence in the context of holding extremist beliefs. These indicate that among violent extremists between 10 and 17% have one or more mental disorders, with a range of psychiatric diagnoses represented, with mood disorder and schizophrenia the most frequent (
5,
6). In recent years, the media has drawn attention to perpetrators who have been formally diagnosed with autism spectrum disorder (ASD) (
2). Examples include the Toronto Van Attack and the Sandy Hook shootings, where, in both instances, the perpetrator had an established diagnosis of ASD. Similarly, among those who are drawn to extremist ideologies or outgroup affiliations, such as
incels (involuntary celibates) (
7), we are aware that a significant minority either have ASD or self-identify with this label (
8). The perpetrator of the Toronto Van Attack is one such individual. Other examples do exist in the literature in which an ASD diagnosis is suggested (
9,
10), but such highly-speculative cases will not be discussed further, particularly given the lack of formal diagnosis and other inherent biases in the approach taken (
11).
It is important to understand the nature of any apparent relationship between diagnosis and behavior in such instances given that it may reflect aspects of vulnerability that characterize ASD and that may be amenable to intervention. Moreover, given that ASD as currently conceptualized has evolved into a relatively prevalent condition [more than 1:54 people, and with a year-on-year rise in prevalence of nearly 10%, (
12)] it is increasingly important to understand the nature of this risk, including its implication for forensic mental health services and the criminal justice system. We set out to critically examine the evidence base concerning the relationship between ASD and acts of violence that are mediated by extremist beliefs. The relationship is, of course, complex, but, as discussed subsequently, red flags can be identified and, as such, it is crucial for mental health and criminal justice professionals to be alert to the possibility of ASD and its potential relevance.