American Psychiatric Association 153rd Annual Meeting
Day 3 - May 16, 2000
Hagop S. Akiskal, MD
Psychiatrists have long been interested in the relationship between seasonality and violence, as well as in the relative contributions of severe mental illness vs substance abuse to the enactment of violent offenses. New studies presented at this year's APA meeting helped to shed some additional light on these topics.[1]
Is it the Time, the Place, or the Season?
Although a great deal has been published on the tendency of suicidal behavior to peak during the spring, there are few broader data on the relationship between seasonality and violence. A study from Norway by Gunnar Morken, MD[2] (Trondheim) and colleagues addressed the latter issue.The researchers examined seasonal variations of all violent crimes in Norway between latitude 58° N and 72° N. Police reports from 1991 to 1997 were obtained from among the nearly 4.5 million inhabitants of the country, divided into 7 cities. More than 82,500 episodes of violence were recorded.
There were 2 peaks for violent crimes: May to June and October to November. The monthly frequency correlated with the absolute value of monthly change of photoperiods (length of daylight for the preceding month).
Latitude was one of the moderating factors in that the monthly ratio of observed to expected episodes increased with latitude. Furthermore, in the most northern latitudes, the increase in violence came a month later.
An analysis of the rates of violence in 512 patients hospitalized for mental illness resulted in the same significant findings in terms of peak incidence in the spring and fall.
The Norwegian data reveal a distinct pattern of seasonal variation in violent crimes, which parallels what we know about seasonal mood and activity change and suicide in the general population.
Substance Abuse and Mental Illness as Factors in Violence
Heather Stuart, PhD,[3] of Queen's University, Kingston, Ontario, Canada, examined the relative contributions of substance abuse vs severe mental illness.This research was conducted within the general framework of destigmatization of mental illness. The driving motive was to: (1) demonstrate that violent crimes by the mentally ill constitute a small proportion of such crimes in the community at large, and (2) further demonstrate that of those with history of mental illness, substance abuse accounts for most such crimes.
Previous research has shown that most violent crimes by the mentally ill are directed against family members and that the incidence is minimal in those who are under current treatment. Most importantly, no more than 3% of all violent crimes in the community are committed by those with psychotic mental disorders. This rate is not significantly higher than the prevalence rates of schizophrenic and affective psychoses combined.
The Canadian researchers studied 1151 violent crimes. They conducted a structured interview based on the DSM-IV scheme (the Structured Clinical Interview for the DSM [SCID]). Forty-five percent of the crimes were committed by individuals who had engaged in substance (mostly alcohol) abuse, 5% by persons who had Axis II, 5% by individuals with mood disorder, 2% by persons with anxiety, 2% by individuals who were psychotic, and 1% by people with other mental disorders. Although 61% of all of these crimes were committed by patients with SCID diagnoses, most were linked to alcohol or other substance abuse. In other words, the proportion by severe mental illness was no more than 10%.
When reviewing the type of crimes that this population committed, it was found that 11% of the crimes were committed against people and 32% against property. Male offenders outnumbered women by a 2:1 ratio; men also had a greater history of multiple offenses.
The findings support the conclusion that mental illness per se contributes only a negligible risk for violent crimes. Alcohol and other substance abuse, on the other hand, represents an important risk.
The methodology raises some questions. First, the relative proportion of personality disorders seen in this study is lower than in other reports. This is because the SCID interview was modified in favor of the Hare criteria for psychopathy, which emphasize traits rather than the criminal behavior emphasized in the DSM-IV schema. This is justified because the DSM-IV definition of antisocial personality by criminal behavior is circular.
In addition, DSM-IV criteria stipulate that alcohol- and other substance-related mood states be disqualified from the diagnosis of mood disorders. But even if the data in the Canadian study were reanalyzed to control for this factor, it would not change the reported statistics to a great extent.
Summary: Implications for Clinical Practice
These studies provide substantial evidence for factors other than mental illness as contributing to violent crimes. These factors have to do with seasonality and substance abuse.Dissemination of these findings will be important for designing prevention efforts to address the factors disclosed in these studies. Most importantly, these data disprove a common misconception in the media and general population that attributes violent crimes to mental illness.
It should be noted that these data -- while quite convincing for Norway and Canada -- need to be replicated in other countries. These 2 countries have low baseline violent crimes, and findings may not generalize to other countries such as the United States, where violent crimes have a higher base and, conceivably, other contributing factors.
All in all, however, the data argue rather convincingly for exculpating mental illness as far as violent crimes are concerned.
References
- Morken G, Stuart, H, Kohn R. The impact of the environment on mental health. Program and abstracts from the 153rd Annual American Psychiatric Association Meeting, May 13-18, 2000; Chicago, Illinois. Abstracts 20-22.
- Morken G. Seasonal variation of violence and latitude. Program and abstracts from the 153rd Annual American Psychiatric Association Meeting, May 13-18, 2000; Chicago, Illinois. Abstract 20.
- Stuart H. Mental illness and violence: is the public at risk? Program and abstracts from the 153rd Annual American Psychiatric Association Meeting, May 13-18, 2000; Chicago, Illinois. Abstract 21.