Premorbid Risk Factors for Violence in Adult Mental Illness

Carl Fulwiler and Robin Ruthazer

The role of premorbid factors in the violence associ- ated with adult mental illness has received l i t t le attention. We previously found that the premorbid onset of substance abuse in early adolescence or childhood was a more powerful predictor of violence in adult patients with chronic mental illness than comorbid substance abuse. In the present study, we retrospectively assessed patients with chronic menta l illness for a history of childhood conduct disorder. Consecutive referrals t o a community treatment team were evaluated with a standardized protocol t ha t included questions about violent behavior. Patients who met DSM-IV criteria for a primary diagnosis of major axis I disorder (N = 64) were assessed for behav- ior prior to age 15 with a checklist for DSM-IV criteria

of conduct disorder using self-report data, supple- mented by collateral information from charts and relatives when possible. About half of the sample had a history of committing violent acts in the community, and 26% met criteria for childhood conduct disorder. The odds of violence in adulthood was 1g-fold higher for subjects with a history of childhood conduct disor- der. Not surprisingly, there was considerable overlap between conduct disorder and early-onset substance abuse. About half of the patients with a history of substance abuse prior to age 15 also had a history of conduct disorder. However, these two premorbid con- ditions appear to be at least partially independent in predicting adult violence in this population. Copyright© 1999by W.B. Saunders Company

V IOLENCE COMMITTED BY PEOPLE with major mental illness living in the community

has major implications for clinical practice, public policy and the law, and public attitudes about mental illness. Although it accounts for only a small portion of the total violence in our society, 1 violence, or the fear of violence, by the mentally ill is a major reason for hospitalization and involun- tary commitment. 2,3 Clinicians, as well as policy- makers, must balance the potential for violence, concern for public safety, and provider liability against clients' liberty, their fight to community treatment, and the costs of treatment.

Several epidemiologic studies have found that comorbidity for substance abuse increases the risk of violence in mental illness. 4-7 Although violence in our society is widely believed to be frequently associated with substance abuse, it has not been possible to clearly demonstrate that intoxication causes violence. 8 Most people do not become violent when intoxicated, even though alcohol or other substances may reduce inhibitions. An alterna- tive explanation for their frequent association is that a common etiology underlies both violence and substance abuse disorders. One prediction of this hypothesis is that they would share childhood

From the Department of Psychiatry, Lemuel Shattuck Hospi- tal and New England Medical Center, Boston; and the Depart- ment of Psychiatry and Division of Clinical Care Research, Tufts University School of Medicine, Boston, MA.

Address reprint requests to Carl Fulwiler, M.D., Ph.D., Department of Psychiatry, MS#1007, New England Medical Center, 750 Washington St, Boston, MA 02111.

Copyright © 1999 by W.B. Saunders Company 0010-440X/99/4002-0001 $10. 00/0

antecedents. Longitudinal studies of alcoholics indicate that the risk of violence is only increased in those with a history of both aggressiveness and alcohol abuse in childhood or early adolescence. 9

The significance of premorbid risk factors for violence associated with mental illness has re- ceived little attention. One study examined the premorbid histories of prisoners with major mental illness and reported that a history of premorbid antisocial behavior was associated with nonviolent, but not violent, criminality. 11 Another study exam- ined official medical and criminal records of a Swedish birth cohort. People who were registered for mental illness were more likely to also be registered for a criminal conviction as adults if they had a history of substance abuse in childhood or early adolescence. 5 The report did not distinguish between violent and nonviolent crime.

In a previous study of outpatients with chronic mental illness, we reported that a history of alcohol or substance abuse beginning prior to age 15 was more strongly associated with adult violence than any other clinical or demographic variable we examined. 12 We have now extended our investiga- tion of premorbid risk factors by assessing the history of childhood conduct disorder in an exten- sion of our original sample. Very-early-onset sub- stance abuse is known to be associated with conduct disorder. 13,14 Since conduct disorder itself is a strong predictor of adult violence, it is possible that our previous results were due to the association between conduct disorder, early-onset substance abuse, and risk of adult violence. In other words, conduct disorder may have been a predisposing factor for the development of early-onset substance

96 Comprehensive Psychiatry, Vol. 40, No. 2 (March/April), 1999: pp 96-100

PREMORBID RISK FACTORS FOR VIOLENCE 97

abuse, as well as for adult violence. Alternatively,

these premorbid factors may act independently to influence the risk of violence in people who

develop mental illness in adulthood.

METHOD

Subjects for this study were all referrals over a 2-year period to the New England Medical Center community treatment team serving Baycove Mental Health Center in Boston. Patients referred to the community treatment team have chronic mental illness and require an intensive level of outpatient services. A total of 118 referrals were made during the referral period (the first 90 referrals over a 1-year period were used in our previous study). 12 Thirty-three referrals were excluded because they were never located or refused to be interviewed and records were not available. Seven additional cases had to be excluded because insufficient information about childhood criteria for conduct disorder were available. Complete information was available for 78 subjects. Using the referral information to compare the excluded cases and the final sample, we found no statistically significant differences for age, gender, or history of alcohol or other substance abuse disorder.

The study design is a cohort analysis comparing patients with and without a history of violence. The information about violence history was obtained by self-report, careful review of all available psychiatric records, and interview with a relative when possible. In a few cases, we also were able to review arrest records. Violence was defined as committing physical or sexual battery against another person, excluding acts of self-defense. Threats of violence or assault without physical contact were not counted. Inpatient assaults were excluded, because staff prac- tices have been shown to influence the incidence and reporting of such assaults? 5,16 Only incidents that took place after the age of 18 and after the patient received a psychiatric diagnosis, or which led directly to their first psychiatric diagnosis, were counted for the purpose of this study.

Clinical and demographic data were collected using a standard- ized intake protocol. Subjects were interviewed by a psychiatrist using a semistructured personal interview. All available hospital and outpatient records were reviewed. When possible, a family member was also interviewed. Diagnoses were made by DSM-IV cr i ter ia . 17 Information about childhood symptoms of conduct disorder was collected using a checklist consisting of DSM-IV criteria to review intake and chart information. In most cases, extensive information about childhood was available from extensive psychosociai histories found in the records of early hospitalizations.

Statistical analysis was performed with SAS software, ver- sion 6.12 for Windows (SAS Institute, Cary, NC). For continu- ous variables, we used t tests to compare violent and nonviolent groups. Dichotomous variables were analyzed using chi-square tests. Logistic regression was used to examine the multivariate relationships of risk factors with the outcome of violence (SAS Software).

RESULTS

The mean age of the sample was 42.4 ___ 12.3

years (mean + SD). Of the subjects, 72% were male, 51% Caucasian, and 37% African-American.

The mean years of education was 10.3 + 2.5. The

mean age for the first diagnosis of mental illness

was 27 + 14 years. The most common DSM-IV diagnoses were schizophrenia (39%) and bipolar

disorder (28%). Additional diagnoses present in

less than 10% of the subjects included the follow- ing: schizoaffective disorder, major depressive dis-

order, obsessive-compulsive disorder, mood disor-

der due to a general medical condition, primary

substance abuse disorders, and personality disor-

ders. A history of alcohol or drug abuse was present

in 73% of the sample.

Almost half (47%) of the total sample had

committed at least one violent act in the community since the age of 18. The most frequent act was

assault and battery, followed by assault and battery with a weapon, rape, and attempted rape. This report focuses on the risk factors that were present

prior to the onset of major mental illness. There-

fore, the following analysis is restricted to subjects

with a diagnosis of schizophrenia, bipolar disorder,

schizoaffective disorder, or major depressive disor-

der, reducing the sample size to 64. The rate of

violence was not significantly different in this

group compared with the remaining subjects with

other diagnoses (48% v 43%, respectively). A comparison of demographic variables in the

subjects with major mental illness showed that

violent subjects were significantly younger at the time of referral to our service and younger at the

time they first received a diagnosis of mental illness

(Table 1). They were also significantly more likely

to be male. There was no significant difference

between the groups for years of education.

The premorbid variables of primary interest in

this study are also shown in Table 1. Violent

subjects were significantly more likely to have

started abusing alcohol or other substances prior to

age 15, as we previously reported in a subset of this

sample. 12 They were also significantly more likely to meet criteria for childhood conduct disorder retrospectively.

We also examined the relationship between

premorbid history and violence risk by construct-

ing logistic regression models with violence as the

dependent variable. Using a history of conduct disorder as the predictor, the odds ratio for violence was almost 10. Since violent patients were signifi- cantly more likely to be male, we controlled for this variable to examine whether the association be- tween violence and conduct disorder could be

98 FULWILER AND RUTHAZER

Table 1. Demographics and Premorbid Risk Factors

Parameter Violent (n = 31) Nonviolent (n = 33) df P

Demographics (mean _+ SD)*

Age at referral (yr)

Age at first diagnosis of major mental illness (yr)

Years of education

Premorbid risk factors (%)t

Gender (male)

Onset of alcohol or drug abuse before age 15

Childhood conduct disorder

38.5 -+ 7.2 48.1 _ 12.2 64 .000

21.9 -+ 7.3 30.9 +- 15.9 61 .012

10.0 + 2.3 10.6 -+ 2.7 72 .292

84 58 1 .021

55 18 1 .002

45 9 1 .002

*ttests.

~X 2 tests.

explained by the gender difference. This decreased the odds ratio for violence, but not significantly (Table 2). There was no interaction effect between conduct disorder and gender (chi-square --- 0.9, e = .35).

The odds ratio for violence was also high when a history of substance abuse beginning prior to age 15 was used as the predictor (Table 2). Although any history of alcohol or drug abuse was strongly associated with violence in our sample (chi- square = 8.9, P < .01), the onset of abuse prior to age 15 performed better in logistic regression models than any history of substance abuse (re- ceiver operating curve [ROC] area = .702 v .686, respectively).

We were interested in the possibility that sub- stance abuse prior to age 15 would strongly predict adult violence because of its association with conduct disorder. Conduct disorder is the anteced- ent of antisocial personality disorder, which in- cludes aggressive behavior. However, we found that only half of the subjects who began abusing

Table 2. Logistic Regression Models for Violence by Risk Factors

95% Odds Confidence ROC

Risk Factor Ratio Interval Area

Conduct disorder 9.7 2.3-39.8 .71

Conduct disorder controlling for

gender 5.3 1.1-24,0 .79

Conduct disorder controlling for

gender and substance abuse

before age 15 9.6 2.0-45.7 .83

Substance abuse before age 15 6.4 2.0-20.2 .70 Substance abuse before age 15 con-

trolling for gender 6.1 1.8-19.9 .76

Substance abuse before age 15 con- trolling for gender and conduct

disorder 3.6 0.9-14.3 .83

Abbreviation: ROC, receiver operating curve.

substances prior to age 15 met the criteria for conduct disorder retrospectively. In a logistic regres- sion model including both premorbid variables, and gender, the odds ratio for violence remained high (Table 2). This was also the only model that yielded an area under the curve greater than .80. The finding that the 95% confidence intervals for the adjusted odds ratios from this model exceed or nearly exceed 1.0 for both conduct disorder and early-onset substance abuse suggests that these factors were at least partially independent in their effect on violence risk.

A potential so~rce of error, given the retrospec- tive design of our study, is that prodromal symp- toms of mental illness at an early age could be confused with symptoms of conduct disorder. We cannot rule out this possibility. However, it appears unlikely that this could have altered our major findings, considering that the age at first diagnosis of the patients with a history of conduct disorder was not significantly less than that of patients without conduct disorder (P = .21).

DISCUSSION

Consistent with previous studies, 4-6 our results indicate that substance abuse is strongly associated with the risk of violence in major mental illness. However, previous studies have not attempted to distinguish whether this association reflects a corre- lation or a causal relationship between the abuse of substances and the risk of violent behavior. As we have reported previously, we found that the onset of substance abuse in adolescence, prior to the onset of mental illness, was even more strongly associ- ated with later violence. In this study, we investi- gated the relationship between this risk factor for violence and another condition that has previously been shown to predict adult violence in the general

PREMORBID RISK FACTORS FOR VIOLENCE 99

population. Not surprisingly, we also found that childhood conduct disorder predicted later violence in people with major mental illness, and we found significant overlap between these premorbid condi- tions. But only about half of the subjects with early-onset substance abuse also met criteria retrospec- tively for childhood conduct disorder, with early-onset substance abuse remaining a strong predictor of violence after controlling for conduct disorder.

The relationship between substance abuse and violence has been difficult to unravel despite the common perception that intoxication makes people more aggressive. Instead, most evidence suggests that people who become violent under the influence of substances have a predisposition toward vio- lence that precedes substance use. For example, prospective follow-up investigations have found that alcoholics who become violent were more likely to be aggressive and abuse substances in childhood and adolescence. 9,1° An important retro- spective study of alcoholics also found that aggres- sive behavior and arrest for violent crimes were associated with teenage-onset alcohol abuse. 2° These results are consistent with findings from the Swed- ish adoption studies of alcoholism and criminality, which reported that early-onset alcohol abuse, often beginning in the teenage years, was associ- ated with a tendency to commit violent cr imes. 18,19

Our results are also consistent with research on penitentiary inmates with mental illness, which found evidence of premorbid risk factors for crimi- nal behavior. A subgroup of this population was found to have a history of antisocial and criminal behavior that began long before the appearance of mental illness. 11,21,22 In the remaining offenders, criminal behavior appeared only after they devel- oped mental illness. In many respects, the offenders with premorbid criminal behavior resembled non- mentally ill inmates more than nonoffenders with mental illness. Specifically, most of these offenders would be considered to have comorbid antisocial disorder.

Comorbidity between major mental illness and antisocial disorder is found not only in prisons. The U.S. Epidemiologic Catchment Area Study found that in a population sample, comorbidity occurred more often than expected by chance. 23,24 Antisocial disorder begins in childhood and often leads to criminal offenses in adolescence and early adult- hood. 14 Thus, it follows that most people with

antisocial disorder who also develop a major men- tal illness will have begun offending prior to the typical age of onset for their mental illness. It is interesting to note in this regard that longitudinal studies of children with conduct disorder show that they are more likely to develop schizophrenia or major affective disorder in adulthood. 14,25 The increased comorbidity between major mental disor- der and antisocial disorder could explain some of the increased rates of crime and violence in the mentally ill, and requires further study.

The premorbid history is usually not emphasized in evaluating violence risk in the mentally ill, or in explanatory models for the increased risk of vio- lence in this population. Our findings suggest that similar mechanisms may operate in early life to influence the risk of adult violence in people with and without major mental illness. Further research is needed to determine how the development of mental illness affects the expression of these early risk factors.

Dysfunction of the brain's serotonergic system has been found repeatedly in people with antisocial disorder, 26,27 impulsive violence, 28,29 and early- onset substance abuse. 3°,31 Despite the robust asso- ciation between serotonin dysfunction and vio- lence, the role of serotonin in the violence associated with major mental disorders remains unknown. The premorbid variables we have studied may identify a subgroup in which serotonin dysfunction is in- volved. Additionally, it will be important to explore the relationship between these premorbid predic- tors and other risk factors that have been identified, such as threat/control override symptoms. 32

Our results cannot be generalized to all people with mental illness. Our sample consists of people with chronic mental illnesses in the public sector. In addition, replication of these findings should in- clude the use of interviewers who are blind to the subjects' history of violence. Future research should also differentiate between different types of vio- lence, and explore the relationship between premor- bid variables and the occurrence of particular psychotic symptoms associated with violent behav- ior. Ultimately, prospective studies will be needed to understand how various risk factors operate in the lives of individuals with mental illness to produce violent behavior. These investigations are needed to develop improved strategies for prevent- ing violence and helping people with mental illness to better integrate into community life.

lOO FULWILER AND RUTHAZER

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