Has the role of mental health problems in mass shootings been significantly underestimated?

Abstract

Prior research suggests that approximately two-thirds of public mass shooters exhibit signs of mental illness. This study analyzed whether that means there are 2 psychological types of perpetrators (some mentally ill, some mentally healthy), or whether almost all perpetrators are likely to have mental health problems. Using a database of 171 public mass shooters who attacked in the United States from 1966 to 2019, we tested for statistically significant differences between perpetrators with and without diagnoses or signs of mental illness. We also closely examined the most lethal perpetrators since 2012, and the most “mentally healthy” perpetrators according to prior coding. Correlates of mental illness were approximately equally common among perpetrators, whether they were believed to be mentally ill or not. Of the variables we examined, data availability provided the best explanation for coding of mental illness, not any trait or life experience. Further evidence suggested that even the most “mentally healthy” perpetrators could be recoded as having signs of mental illness or suicidality, or were clear outliers, or may not qualify as public mass shooters. The most lethal perpetrators exhibited signs of mental illness or suicidal intent (or both) in all cases. When people engage in concerning behaviors that suggest a mass shooting risk, their mental health should be carefully assessed alongside other warning signs. However, it is important to avoid treating people with mental illness like criminals, because social stigma reduces the likelihood that they will ask for, and receive, the psychological help they need.

A Sequence Analysis of the Behaviors and Experiences of the Deadliest Public Mass Shooters

“…Numerous prior studies have found some form of mental health diagnosis, problem, or concern in a substantial percentage of public mass shooters, ranging from 41% to 90% (Duwe, 2020; Gill et al, 2017; Newman et al, 2004; Peterson & Densley, 2019; Silver et al, 2018; Vossekuil et al, 2002). Lankford and Cowan’s (2020) recent study even demonstrates these data may underestimate the prevalence of mental health problems in public mass shootings. Nonetheless, these studies examine lifetime prevalence, meaning the mental illness or symptoms may have appeared long before the attack and leaving open the possibility that the attacker was no longer exhibiting any symptoms in the months or even years preceding violence (Skeem & Mulvey, 2020).…”

“…Some of these efforts have focused on individual factors that scholarship, media coverage, and intuition suggest have explanatory power. For example, one frequently considered factor is the presence (or absence) of mental illness (Dutton et al, 2013; Fox & Fridel, 2016; Gill et al, 2017; Lankford & Cowan, 2020; Metzl & MacLeish, 2015; Vossekuil et al, 2002). The spectrum of factors considered also includes criminal histories (DeLisi & Scherer, 2006; DeLisi & Walters, 2011), fame-seeking behaviors (Lankford, 2016; Silva & Greene-Colozzi, 2019b), illegal drug use (Miller et al, 2020), masculinity norms (Kalish & Kimmel, 2010; Madfis, 2014; Silva et al, 2021), and contagion and copycat effects (Boyd & Molyneux, 2021; Lankford & Tomek, 2018; Towers et al, 2018).…”

An epidemiological analysis of public mass shooters and active shooters: Quantifying key differences between perpetrators and the general population, homicide offenders, and people who die by suicide.

“…This was the most reasonable parallel we could make for a broad measure of mental health problems. Relying solely on formal diagnoses would provide a major underestimate, given the frequency of doctor avoidance and underdiagnosis (Lankford & Cowan, 2020).…”

The pathway to violence and public mass shooters in mental health treatment before attacks

“…An essential aspect of a mental health provider's role is engaging in risk assessment and mitigation when a patient presents with suicidal or homicidal ideation (Cowan and Cole, 2020;Lankford and Cowan, 2020;Borum and Reddy, 2001;Borum et al, 1999;Hagga ˚rd-Grann, 2007;Kivisto, 2016;Lankford, 2018;Parke et al, 2018). In most states, due to the Tarasoff v. Regents of the University of California, 17 Cal.3d 425 (1976) ruling, mental health professionals have a duty to warn and protect potential victims when a patient threatens violence (Adi and Mathbout, 2018;Borum and Reddy, 2001;Hagga ˚rd-Grann, 2007;Kivisto, 2016;National Conference of State Legislatures, 2018;Parke et al, 2018).…”