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Mental illness and violence

Multiple interacting factors contribute to violent behavior.

Public opinion surveys suggest that many people think mental illness and violence go hand in hand. A 2006 national survey found, for example, that 60% of Americans thought that people with schizophrenia were likely to act violently toward someone else, while 32% thought that people with major depression were likely to do so. In fact, research suggests that this public perception does not reflect reality. Most individuals with psychiatric disorders are not violent. Although a subset of people with psychiatric disorders commit assaults and violent crimes, findings have been inconsistent about how much mental illness contributes to this behavior and how much substance abuse and other factors do.

An ongoing problem in the scientific literature is that studies have used different methods to assess rates of violence — both in people with mental illness and in control groups used for comparison. Some studies rely on "self-reporting," or participants' own recollection of whether they have acted violently toward others. Such studies may underestimate rates of violence for several reasons. Participants may forget what they did in the past, or may be embarrassed about or unwilling to admit to violent behavior. Other studies have compared data from the criminal justice system, such as arrest rates among people with mental illness and those without. But these studies, by definition involving a subset of people, may also misstate rates of violence in the community. Finally, some studies have not controlled for the multiple variables beyond substance abuse that contribute to violent behavior (whether an individual is mentally ill or not), such as poverty, family history, personal adversity or stress, and so on.

The MacArthur Violence Risk Assessment Study was one of the first to address the design flaws of earlier research by using three sources of information to assess rates of violence. The investigators interviewed participants multiple times, to assess self-reported violence on an ongoing basis. They verified participants' recollections by checking with family members, case managers, or other people familiar with the participants. Finally, the researchers also checked arrest and hospitalization records.

The study found that 31% of people who had both a substance abuse disorder and a psychiatric disorder (a "dual diagnosis") committed at least one act of violence in a year, compared with 18% of people with a psychiatric disorder alone. This confirmed other research that substance abuse is a key contributor to violent behavior. But when the investigators probed further, comparing rates of violence in one area in Pittsburgh in order to control for environmental factors as well as substance use, they found no significant difference in the rates of violence among people with mental illness and other people living in the same neighborhood. In other words, after controlling for substance use, rates of violence reported in the study may reflect factors common to a particular neighborhood rather than the symptoms of a psychiatric disorder.

Several studies that have compared large numbers of people with psychiatric disorders with peers in the general population have added to the literature by carefully controlling for multiple factors that contribute to violence.

In two of the best designed studies, investigators from the University of Oxford analyzed data from a Swedish registry of hospital admissions and criminal convictions. (In Sweden, every individual has a unique personal identification number that allowed the investigators to determine how many people with mental illness were convicted of crimes and then compare them with a matched group of controls.) In separate studies, the investigators found that people with bipolar disorder or schizophrenia were more likely — to a modest but statistically significant degree — to commit assaults or other violent crimes when compared with people in the general population. Differences in the rates of violence narrowed, however, when the researchers compared patients with bipolar disorder or schizophrenia with their unaffected siblings. This suggested that shared genetic vulnerability or common elements of social environment, such as poverty and early exposure to violence, were at least partially responsible for violent behavior. However, rates of violence increased dramatically in those with a dual diagnosis (see "Rates of violence compared").

Taken together with the MacArthur study, these papers have painted a more complex picture about mental illness and violence. They suggest that violence by people with mental illness — like aggression in the general population — stems from multiple overlapping factors interacting in complex ways. These include family history, personal stressors (such as divorce or bereavement), and socioeconomic factors (such as poverty and homelessness). Substance abuse is often tightly woven into this fabric, making it hard to tease apart the influence of other less obvious factors.

Rates of violence compared

Assessing risk of violence

Highly publicized acts of violence by people with mental illness affect more than public perception. Clinicians are under pressure to assess their patients for potential to act in a violent way. Although it is possible to make a general assessment of relative risk, it is impossible to predict an individual, specific act of violence, given that such acts tend to occur when the perpetrator is highly emotional. During a clinical session, the same person may be guarded, less emotional, and even thoughtful, thereby masking any signs of violent intent. And even when the patient explicitly expresses intent to harm someone else, the relative risk for acting on that plan is still significantly influenced by the following life circumstances and clinical factors.

History of violence. Individuals who have been arrested or acted violently in the past are more likely than others to become violent again. Much of the research suggests that this factor may be the largest single predictor of future violence. What these studies cannot reveal, however, is whether past violence was due to mental illness or some of the other factors explored below.

Substance use. Patients with a dual diagnosis are more likely than patients with a psychiatric disorder alone to become violent, so a comprehensive assessment includes questions about substance use in addition to asking about symptoms of a psychiatric disorder.

One theory is that alcohol and drug abuse can trigger violent behavior in people with or without psychiatric disorders because these substances simultaneously impair judgment, change a person's emotional equilibrium, and remove cognitive inhibitions. In people with psychiatric disorders, substance abuse may exacerbate symptoms such as paranoia, grandiosity, or hostility. Patients who abuse drugs or alcohol are also less likely to adhere to treatment for a mental illness, and that can worsen psychiatric symptoms. Another theory, however, is that substance abuse may be masking, or entwined with, other risk factors for violence. A survey of 1,410 patients with schizophrenia participating in the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) study, for example, found that substance abuse and dependence increased risk of self-reported violent behavior fourfold. But when the researchers adjusted for other factors, such as psychotic symptoms and conduct disorder during childhood, the impact of substance use was no longer significant.

Personality disorders. Borderline personality disorder, antisocial personality disorder, conduct disorder, and other personality disorders often manifest in aggression or violence. When a personality disorder occurs in conjunction with another psychiatric disorder, the combination may also increase risk of violent behavior (as suggested by the CATIE study, above).

Nature of symptoms. Patients with paranoid delusions, command hallucinations, and florid psychotic thoughts may be more likely to become violent than other patients. For clinicians, it is important to understand the patient's own perception of psychotic thoughts, because this may reveal when a patient may feel compelled to fight back.

Age and gender. Young people are more likely than older adults to act violently. In addition, men are more likely than women to act violently.

Social stress. People who are poor or homeless, or otherwise have a low socioeconomic status, are more likely than others to become violent.

Personal stress, crisis, or loss. Unemployment, divorce, or separation in the past year increases a patient's risk of violence. People who were victims of violent crime in the past year are also more likely to assault someone.

Early exposure. The risk of violence rises with exposure to aggressive family fights during childhood, physical abuse by a parent, or having a parent with a criminal record.

Preventing violence

The research suggests that adequate treatment of mental illness and substance abuse may help reduce rates of violence. For example, in one study, the CATIE investigators analyzed rates of violence in patients who had earlier been randomly assigned to antipsychotic treatment. (Patients' own recollections were double-checked with family members.) This study found that most patients with schizophrenia who took antipsychotics as prescribed were less likely to be violent than those who did not. An exception to this general trend occurred in participants who were diagnosed with a conduct disorder during childhood. No medication proved better than the others in reducing rates of violence, but this study excluded clozapine (Clozaril).

This is important because both the CATIE investigators and other researchers cite evidence that clozapine appears more effective than other psychotics in reducing aggressive behavior in patients with schizophrenia and other psychotic disorders. One study found, for example, that patients with a diagnosis of schizophrenia or another psychotic disorder who were treated with clozapine had significantly lower arrest rates than those taking other drugs. The study was not designed to determine whether this was due to the drug itself or the fact that clozapine treatment requires frequent follow-ups that might encourage patients to continue taking it as prescribed.

Indeed, as with psychiatric treatment in general, medication treatment alone is unlikely to reduce risk of violence in people with mental illness. Interventions ideally should be long-term and include a range of psychosocial approaches, including cognitive behavioral therapy, conflict management, and substance abuse treatment.

Of course, this sort of ideal treatment may be increasingly difficult to achieve in the real world, given reductions in reimbursements for mental health services, ever-shorter hospital stays, poor discharge planning, fragmented care in the community, and lack of options for patients with a dual diagnosis. The Schizophrenia Patient Outcomes Research Team (PORT) guidelines, for example, outlined the type of multimodal treatment necessary to increase chances of full recovery. Most patients with schizophrenia do not receive the kind of care outlined in the PORT recommendations. Solutions to these challenges will arise not from clinicians, but from policy makers.

The prevalence and treatment of mental illness today

The first large survey of mental illness and its treatment since the early 1990s shows that almost half of adult Americans at some time, and nearly a quarter in any given year, have had a psychiatric disorder. More of them are getting treatment today than in the early 1990s, but the treatment is still usually delayed and inadequate.

The study, called the National Comorbidity Survey Replication, was conducted in 2001–2003 with funding from the National Institute of Mental Health and a number of academic institutions and foundations.

Interviewers used a standard format to question a representative sample of more than 9,000 adults. At some time in their lives, nearly 46% had at least one psychiatric disorder (as defined by the American Psychiatric Association's diagnostic manual). The rate was highest for anxiety disorders, including panic disorder, generalized anxiety, social anxiety, phobias, and post-traumatic stress disorder (29%). Next came impulse control disorders, including attention deficit hyperactivity disorder, conduct disorder, and oppositional defiant disorder (25%). Twenty-one percent had had a mood disorder and 15% had been dependent on or an abuser of alcohol or other drugs.

The most common individual psychiatric disorders were major depression (17%), alcohol abuse (13%), social anxiety disorder (12%), and conduct disorder (9.5%). Women were more likely to have had anxiety and mood disorders, men more likely to have had impulse control disorders. Different disorders often went together, especially anxiety and depression. About 28% of the population suffered more than one psychiatric disorder.

In the previous year, 26% of those interviewed had had a psychiatric disorder. Again, anxiety disorders were the most common (18%), followed by mood disorders (9.5%), impulse control disorders (9%), and substance abuse and dependence (4%).

Psychiatric disorders began early in life — in half of cases before age 14 and in three-fourths of cases before age 24. On average, anxiety and impulse control disorders first appeared at age 11, substance abuse at age 20, and depression at age 30.

Study authors define a "severe" disorder as one involving a suicide attempt, psychosis, severe drug dependence, serious violence, substantial disability or limitation, or being "out of role," that is, unable to function normally in family life, at work, and in personal relationships, for a month or more. By this definition, 22% of psychiatric disorders were severe, and 6% of the population had a severe psychiatric disorder in the previous year.

These numbers may be an underestimate. Some people must have failed to recall symptoms (especially chronic mild to moderate depression) or failed to report them because of shame and stigma. Homeless and institutionalized persons were excluded from the survey. The rate of response was 71%, and people who declined to participate probably had a higher than average rate of psychiatric illness.

Interviewers went on to ask: "Have you ever been treated for problems with your emotions or nerves or your use of alcohol or drugs?" About 80% of people with a psychiatric disorder had eventually sought treatment, but often only after a long delay — the average was 10 years after symptoms first appeared. Major depression and panic disorder were usually treated fairly quickly, but fewer than 7% sought treatment for social anxiety disorder, post-traumatic stress disorder, and attention deficit disorder within the first year. And nearly half of those with impulse control or drug problems had never sought help at all.

About 17% of the interviewees, including 41% of those with a psychiatric disorder, said they had used mental health services in the previous year. Women were more likely to use these services than men, and whites more than blacks and Latinos with similar symptoms.

Family doctors, nurses, and other general medical professionals provided treatment for 23%; psychiatrists for 12%; other mental health professionals such as social workers and psychologists for 16%; counselors or spiritual advisers for 8%; and complementary and alternative practitioners (including self-help groups) for 7%. (The total is more than 41% because some people received treatment from more than one source.)

Most of this treatment was inadequate, at least by the standards applied in the survey. The researchers defined minimum adequacy as a suitable medication at a suitable dose for two months, along with at least four visits to a physician; or else eight visits to any licensed mental health professional. By that definition, only 33% of people with a psychiatric disorder were treated adequately, and only 13% of those who saw general medical practitioners.

A comparison with the original National Comorbidity Survey, conducted in 1991–1992, showed that Americans have been increasing their use of mental health services. The proportion of the population receiving treatment in the previous year rose more than 50% during the decade, mostly because of more visits to psychiatrists and other physicians.

It may be surprising to learn that 46% of the American population has been mentally ill at some time. But more than 99% of us will have a significant physical illness at some time in our lives, and even mild to moderate psychiatric disorders can be as harmful as chronic physical illness. Major depression, for example, causes more disability and misery than most medical disorders. And many psychiatric disorders are life-threatening — consider the relationship between alcoholism and accidental death, or between depression and suicide. Also, unlike most physical illnesses, mental illness usually begins in youth and affects people in the prime of life.

Treatment has become more widespread since the early 1990s because of greater public awareness, more effective diagnosis, less stigma, more screening and outreach programs, and greater availability of medications. Most important, according to the survey researchers, has been the growing willingness of general practitioners to prescribe psychoactive medications, especially antidepressants.

Still, at the beginning of the 21st century nearly 60% of people with psychiatric disorders were getting no treatment. And partly because most treatment was still inadequate, the overall rate of mental illness did not change between 1991–92 and 2001–2003. According to survey researchers, one reason may be that many physicians lack the time, training, and experience needed to persuade patients to keep taking medications and make return visits.

Some researchers point out that the problem may not be as serious as it seems. People often recover spontaneously from psychiatric disorders, as they do from physical illnesses. And, as with physical illnesses, sometimes there is no reliable treatment. But it can be hard to determine when treatment will be unnecessary or ineffective. The question is whether we need to detect mild symptoms earlier so that they won't get worse, or concentrate resources on the more severe (and less common) types of chronic mental illness. Survey researchers also suggest that we need more outreach and voluntary screening, more education about mental illness for the public and physicians, and more effort to treat substance abuse and impulse control disorders.

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