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Mental Illness, disorder characterized by disturbances in a person’s thoughts, emotions, or behavior. The term mental illness can refer to a wide variety of disorders, ranging from those that cause mild distress to those that severely impair a person’s ability to function. Mental health professionals sometimes use the terms psychiatric disorder or psychopathology to refer to mental illness.
Severe mental illness almost always alters a person’s life dramatically. People with severe mental illnesses experience disturbing symptoms that can make it difficult to hold a job, go to school, relate to others, or cope with ordinary life demands. Some individuals require hospitalization because they become unable to care for themselves or because they are at risk of committing suicide.
The symptoms of mental illness can be very distressing. People who develop schizophrenia may hear voices inside their head that say nasty things about them or command them to act in strange or unpredictable ways. Or they may be paralyzed by paranoia—the deep conviction that everyone, including their closest family members, wants to injure or destroy them. People with major depression may feel that nothing brings pleasure and that life is so dreary and unhappy that it is better to be dead. People with panic disorder may experience heart palpitations, rapid breathing, and anxiety so extreme that they may not be able to leave home. People who experience episodes of mania may engage in reckless sexual behavior or may spend money indiscriminately, acts that later cause them to feel guilt, shame, and desperation.
Other mental illnesses, while not always debilitating, create certain problems in living. People with personality disorders may experience loneliness and isolation because their personality style interferes with social relations. People with an eating disorder may become so preoccupied with their weight and appearance that they force themselves to vomit or refuse to eat. Individuals who develop post-traumatic stress disorder may become angry easily, experience disturbing memories, and have trouble concentrating.
Experiences of mental illness often differ depending on one’s culture or social group, sometimes greatly so. For example, in most of the non-Western world, people with depression complain principally of physical ailments, such as lack of energy, poor sleep, loss of appetite, and various kinds of physical pain. Indeed, even in North America these complaints are commonplace. But in the United States and other Western societies, depressed people and mental health professionals who treat them tend to emphasize psychological problems, such as feelings of sadness, worthlessness, and despair. The experience of schizophrenia also differs by culture. In India, one-third of new cases of schizophrenia involve catatonia, a behavioral condition in which a person maintains a bizarre statuelike pose for hours or days. This condition is rare in Europe and North America.
With appropriate treatment, most people can recover from mental illness and return to normal life. Even those with persistent, long-term mental illnesses can usually learn to manage their symptoms and live productive lives.
In most societies mental illness carries a substantial stigma, or mark of shame. The mentally ill are often blamed for bringing on their own illnesses, and others may see them as victims of bad fate, religious and moral transgression, or witchcraft. Such stigma may keep families from acknowledging that a family member is ill. Some families may hide or overprotect a member with mental illness—keeping the person from receiving potentially effective care—or they may reject the person from the family. When magnified from individuals to a whole society, such attitudes lead to underfunding of mental health services and terribly inadequate care. In much of the world, even today, the mentally ill are chained, caged, or hospitalized in filthy, brutal institutions. Yet attitudes toward mental illness have improved in many areas, especially owing to health education and advocacy for the mentally ill.
Mental illness creates enormous social and economic costs. Depression, for example, affects some 500 million people in the world and results in more time lost to disability than such chronic diseases as diabetes mellitus and arthritis. Estimating the economic cost of mental illness is complex because there are direct costs (actual medical expenditures), indirect costs (the cost to individuals and society due to reduced or lost productivity, for example), and support costs (time lost to care of family members with mental illnesses). One study estimated that in 1985 the economic costs of mental illness in the United States totaled $103.7 billion. Of this, treatment and support costs totaled $42.5 billion, which represented 11.5 percent of the total cost of care for all illnesses.
Another method of estimating the cost of mental illness to society measures the impact of premature deaths and disablements. Research by the World Health Organization and the World Bank estimated that in 1990, among the world’s population aged 15 to 44 years, depression accounted for more than 10 percent of the total burden attributable to all diseases. Two other illnesses, bipolar disorder and schizophrenia, accounted for another 6 percent of the burden. This research has helped governments recognize that mental illnesses constitute a far greater challenge to public health systems than previously realized.
No universally accepted definition of mental illness exists. In general, the definition of mental illness depends on a society’s norms, or rules of behavior. Behaviors that violate these norms are considered signs of deviance or, in some cases, of mental illness.
Because norms vary between cultures, behaviors considered signs of mental illness in one culture may be considered normal in other cultures. For example, in the United States, a person who experiences trance and possession states (altered states of consciousness) is usually diagnosed as suffering from a mental illness. Yet, in many non-Western countries, people consider such states an essential part of human experience. In Native American culture, it is common for people to hear the voices of recently deceased loved ones. In contrast, most mental health professionals in Western cultures would consider such behavior a possible symptom of schizophrenia or psychosis.
The variation in behavioral norms does not mean, however, that definitions of mental illness are necessarily incompatible across cultures. Many behaviors are recognized throughout the world as being indicative of mental illness. These include extreme social withdrawal, violence to oneself, hallucinations (false sensory perceptions), and delusions (fixed, false ideas).
Another way of defining mental illness is based on whether a person’s behaviors are maladaptive—that is, whether they cause a person to experience problems in coping with common life demands. For example, people with social phobia may avoid interacting with other people and experience problems at work as a result. Critics note that under this definition, political dissidents could be considered mentally ill for refusing to accept the dictates of their government.
Prevalence of Mental Disorders
This chart illustrates the percentage of people in the United States who experience a particular class of mental illness at some point during their lives. The figures are derived from the National Comorbidity Survey, in which researchers interviewed more than 9,000 people over 18 years of age.
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Mental illness affects people of all ages, races, cultures, and socioeconomic classes. The prevalence of mental illness refers to how many people experience a mental illness during a specified time period.
In the United States, researchers estimate that about 24 percent of people 18 or older, or about 44 million adults, experience a mental illness or substance-related disorder during the course of any given year. The most common of these disorders are depression, alcohol dependence (see alcoholism), and various phobias (irrational fears of things or situations). An estimated 2.6 percent of adults in the United States, or about 4.8 million people, suffer from a severe and persistent mental illness—such as schizophrenia, bipolar disorder, or a severe form of depression or panic disorder—in any given year. An additional 2.8 percent of adults, or about 5.2 million people, experience a mental illness that seriously interferes with one or more aspects of their daily life, such as their ability to work or relate to other people. All of these figures exclude people who are homeless and those living in prisons, nursing homes, or other institutions—populations that have high rates of mental illness.
International surveys have demonstrated that from 30 to 40 percent of people in a given population experience a mental illness during their lives. These surveys also reveal that anxiety disorders are usually even more common than depression.
Young people can suffer from mental illnesses and psychological problems just as adults can. Prevalence estimates in industrialized countries indicate that from 14 to 20 percent of individuals under age 18 suffer from a diagnosable mental disorder. In the United States, an estimated 9 to 13 percent of children between the ages of 9 and 17 suffer from a serious emotional disturbance—that is, a disorder that severely disrupts a child's daily functioning in the family, school, or community.
Anxiety disorders are the most common childhood mental disorders, affecting an estimated 8 to 10 percent of children and adolescents in the United States. Children with these disorders experience persistent, unrealistic worry or uneasiness that interferes with their ability to function normally. About 4 percent of children and young adolescents experience severe separation anxiety and worry excessively about becoming separated from their parents. Depression is another common childhood mental disorder, affecting up to 2.5 percent of children (under age 13) and up to 8.3 percent of adolescents in the United States. Depression in children can lead to failure in school, poor self-image, troubled social relations, and even suicide.
A number of mental disorders are usually first diagnosed in infancy, childhood, or adolescence. Autism is a relatively rare disorder that appears before the age of three and severely impairs a child's ability to interact socially and to communicate with others. Attention-deficit hyperactivity disorder begins before the age of seven. Its symptoms include an inability to sit still, focus attention, or control impulses. Eating disorders, such as anorexia nervosa and bulimia nervosa (see Bulimia), most often affect adolescent girls.
With a greater percentage of people living beyond the age of 65—both in the industrialized nations of the West and the developing countries of Asia, Africa, and Latin America—the problem of mental illness among the elderly has grown significantly. Researchers estimate that from 15 to 25 percent of elderly people in the United States suffer from significant symptoms of mental illness. Dementia, characterized by confusion, memory loss, and disorientation, occurs mostly among the elderly. A study of residents of Boston, Massachusetts, revealed that about 10 percent of people over the age of 65 suffer from Alzheimer’s disease, the most common form of dementia, and research on residents of Shanghai, China found that 4.6 percent of people over 65 suffer from this condition.
Major depression, the most severe form of depression, affects from 1 to 2 percent of people aged 65 or older who are living in the community (rather than in nursing homes or other institutions). The prevalence of depression and other mental illnesses is much higher among elderly residents of nursing homes. Although most older people with depression respond to treatment, many cases of depression among the elderly go undetected or untreated. Research indicates that depression is a major risk factor for suicide among the elderly in the United States. People over age 65 in the United States have the highest suicide rate of any age group.
Like physical diseases, the highest rates of mental illness occur among people in the lower socioeconomic classes, especially those living in severe poverty. Rates of almost all mental illnesses decline as levels of income and education increase. A national survey published in 1994 indicated that people who earned $19,000 or less annually in the United States were twice as likely to have experienced an anxiety disorder as people who earned $70,000 or more. The hardships associated with poverty seem to contribute to the development of some mental illnesses, particularly anxiety disorders and depression. In addition, debilitating mental illnesses, such as schizophrenia, may cause individuals to drift to lower socioeconomic classes.
Generally, the overall prevalence rates of mental illnesses among men and women are similar. However, men have much higher rates of antisocial personality disorder and substance abuse. In the United States, women suffer from depression and anxiety disorders at about twice the rate of men. The gender gap is even wider in some countries. For example, in China, women suffer from depression at nine times the rate of men.
Mental illness is becoming an increasing problem for two reasons. First, increases in life expectancy have brought increased numbers of certain chronic mental illnesses. For example, because more people are living into old age, more people are suffering from dementia. Second, a number of studies provide evidence that rates of depression are rising throughout the world. The reasons may be related to such factors as economic change, political and social violence, and cultural disruptions. While some have questioned these findings, dramatic increases in the numbers of refugees and people dislocated from their homes by economic forces or civil strife are associated with great increases in a variety of mental illnesses for those populations. According to the United Nations High Commissioner for Refugees, the number of refugees worldwide increased from 2.5 million in 1971 to 13.2 million in 1996, peaking at 17 million in 1991.
A number of mental illnesses—such as depression, anxiety disorders, schizophrenia, and bipolar disorder—occur worldwide. Others seem to occur only in particular cultures. For example, eating disorders, such as anorexia nervosa (compulsive dieting associated with unrealistic fears of fatness), occur mostly among girls and women in Europe, North America, and Westernized areas of Asia, whose cultures view thinness as an essential component of female beauty. In Latin America, people who experience overwhelming fright after a dangerous or traumatic event are said to have susto (fright), an illness in which their soul has been frightened away. In some societies of West Africa and elsewhere, brain fag describes individuals (usually students) who experience difficulties in concentrating and thinking, as well as physical symptoms of pain and fatigue.
Most mental health professionals in the United States use the Diagnostic and Statistical Manual of Mental Disorders(DSM), a reference book published by the American Psychiatric Association, as a guide to the different kinds of mental illnesses. The fourth edition, known as DSM-IV, describes more than 300 mental disorders, behavioral disorders, addictive disorders, and other psychological problems and groups them into broad categories. This article describes some of the major categories, including anxiety disorders, mood disorders, schizophrenia and other psychotic disorders, personality disorders, cognitive disorders, dissociative disorders, somatoform disorders, factitious disorders, substance-related disorders, eating disorders, and impulse-control disorders. Mental health professionals in many other parts of the world use a different classification system, the International Classification of Diseases (ICD), published by the World Health Organization.
The DSM and ICD are both categorical systems of classification, in which each mental illness is defined by its own unique set of symptoms and characteristics. In theory, each disorder should possess diagnostic criteria that are independent of one another, just as tuberculosis and lung cancer are discrete diseases. Yet symptoms of many mental disorders overlap, and many people—such as those who experience both depression and severe anxiety—show symptoms of more than one disorder at the same time. For these reasons, some mental health professionals advocate a dimensional system of classification. In contrast to the categorical approach, which sees mental disorders as qualitatively distinct from normal behavior, a dimensional system views behavior as falling along a continuum of normality, with some behaviors considered more abnormal than others. In a dimensional system, diagnoses do not describe discrete diseases but rather portray the relative importance of an array of symptoms.
Definitions and classifications of mental illnesses change as research improves understanding of them. For example, DSM-IV allows a diagnosis of schizophrenia only when characteristic symptoms have lasted at least one month, whereas the previous edition of DSM required a duration of only one week.
Anxiety disorders involve excessive apprehension, worry, and fear. People with generalized anxiety disorder experience constant anxiety about routine events in their lives. Phobias are fears of specific objects, situations, or activities. Panic disorder is an anxiety disorder in which people experience sudden, intense terror and such physical symptoms as rapid heartbeat and shortness of breath. People with obsessive-compulsive disorder experience intrusive thoughts or images (obsessions) or feel compelled to perform certain behaviors (compulsions). People with post-traumatic stress disorder relive traumatic events from their past and feel extreme anxiety and distress about the event.