Delusions, especially paranoid ones, lead to violence, right? Well maybe it isn’t quite so clear.
The MacArthur Study of Mental Disorder and Violence followed 1136 patients who’d been admitted to acute care psychiatric units and measured a whole slew of factors at 10 week intervals for a year. In a 2003 article Violence and mental illness: an overview Dr. Stuart writes that the MacArthur Study “stands out as the most sophisticated attempt to date to disentangle [the] complex interrelationships” between mental illness and violence. The resulting book Rethinking Risk Assessment is worth a read.
In setting up the question the authors write (bold is mine):
“Delusions and violence have long been linked in the minds of both lay people and mental health professionals. Indeed in the popular media, the prototypical dangerous mental patient is driven by “crazy ideas,” often stoked by hallucinated voices, to commit unspeakable acts of violence. The professional literature has numerous case reports detailing the link between delusions and violence. Even though systematic studies of forensic and civil patient populations have confirmed that most violence perpetrated by psychotic persons is not motivated by delusions, a substantial minority of their violent acts appears to stem from their delusional thoughts. Although no one would quarrel with the conclusion that violence may be precipitated by delusions, these studies fail to address the question of whether delusional persons are more violent than other persons with or without mental illness.”
Reporting their results the researchers note that “…delusions at baseline did not have a significant relationship with violence during the first 20 weeks, but did have a weakly significant negative relationship with violence over the entire year of follow up. That is, subjects who were delusional in the hospital were less likely to be violent after discharge… The presence of violent content in the delusions, even if the violence was directed toward others, did not predict violence during the follow up period.”
They point out that “Contrary to popular wisdom and to the results of several studies, the data from this study suggest that the presence of delusions does not predict higher rates of violence among recently discharged psychiatric patients… On the other hand, nondelusional suspiciousness – perhaps involving a tendency toward misperception of others’ behavior as indicating hostile intent – does appear to be linked with subsequent violence and may account for the findings of previous studies.”
The authors do temper their conclusion by pointing out that “These data, of course, should not be taken as evidence that delusions never cause violence. It is clear from clinical experience and from many other studies that they can and do.”
As to why, they note that “delusions are often associated with chronic psychotic conditions, which are frequently attended by social withdrawal and the development of smaller social networks. Delusional subjects in the community, therefore, may have less desire and fewer opportunities to engage in the interpersonal interactions that lead to violence compared with less severely ill patients.”
Fascinating – the presence of delusions, even violent ones, did not predict violent acts.
No matter how you look at the prediction of violence we always seem to come back to Yogi Berra’s wisdom that “It’s tough to make predictions, especially about the future.”
In an upcoming blogpost- MacArthur part 2: What’s the relationship between hallucinations and violence?