Mental illness encompasses a heterogenous group of disorders ranging from exaggerated response to stressful events to altered mentation from specific neurologic or genetic abnormalities. In any 6-month period, an estimated 29.4 million Americans, or 18.7% of the U.S. population, suffer from one or more of the mental disorders described by the Diagnostic Interview Schedule. Among males, the most frequent mental disorders are alcohol abuse/dependence, phobia, drug abuse/dependence, and dysthymia (prolonged minor depression). Among females, the most common mental disorders are phobia, major depressive episode without grief, dysthymia, and obsessive-compulsive disorders.

Anxiety disorders are the most prevalent (8.3% 6-month prevalence) of all mental illnesses and include phobias, panic states, obsessive-compulsive disorder and somatization. Substance-use disorders are the next most prevalent mental disorders (6.4% 6-month prevalence), especially among males and include both alcohol and drug abuse and dependence. Affective disorders are also highly prevalent (6.0% 6-month prevalence) and include major depression, bipolar depressive disorder (depression accompanied by manic episodes) and dysthymia. Schizophrenia, antisocial personality disorder and severe cognitive impairment are less common, each having a 6-month prevalence of about 1%.

Determining the prevalence of mental illness and identifying groups at high risk provide clues to etiology and prevention in addition to providing a basis for policy decisions regarding allocation of resources. Epidemiologic studies of mental illness, however, have been difficult to interpret because of the variability in case definition, unreliability of psychiatric diagnosis, and limitations of sample size or selection. In 1981-82, the National Institute of Mental Health (NIMH) undertook a collaborative 5-site Epidemiology Catchment Area Program (ECA), designed to assess mental disorder prevalence, incidence, and service use in almost 20,000 community and institutional residents of the U.S. Each subject was interviewed with the NIMH Diagnostic Interview Schedule (DIS), which allows lay interviewers to assess the presence, duration, and severity of symptoms necessary for the diagnostic criteria of the Diagnostic Statistical Manual (DSM-III). Using a longitudinal design, the ECA study incorporated at least 2 face-to-face interviews (1 year apart) and 1 intervening telephone or direct interview. The information that follows includes 6-month prevalence, lifetime prevalence and service utilization data based on the community data from the first 3 ECA sites (New Haven, Connecticut; Baltimore, Maryland; and St. Louis, Missouri). Since these sites were not chosen as a representative sample of the U.S. population, the figures are reported as a range from all three sites, with the exception of the first table, which is a projection for the nation as a whole.

Incidence and Prevalence

Substance Abuse Disorders

[Substance abuse is defined in the DSM-III as a pattern of pathological use, in which the disturbance needs to last at lease one month; however, the disturbance need not be exhibited constantly during the month. There must be exhibited impairment in social or occupational functioning caused by the pattern of pathological use.]

According to the results of the study conducted in the first three sites of the 1982 ECA study, the overall lifetime prevalence of substance abuse disorders was 13.0%-18.1%. The corresponding 6-month prevalence for substance-abuse disorders was 5.8%-7.2%.

The lifetime prevalence of alcohol abuse/dependence in three ECA study sites in 1982 was 15.0%-18.1%. The 6-month (or current) prevalence of alcohol abuse/dependence was 4.5%-5.7% in the same study.

The lifetime prevalence of drug abuse/dependence at three ECA sites in 1982 was 5.5%-5.8%. The 6-month (current) prevalence of drug abuse/dependence was 1.8%-2.2% in the same study.

Schizophrenia

The lifetime prevalence of schizophrenia ranged from 1.0%-1.9% in three sites of the ECA study. The 6-month prevalence of schizophrenia or schizophreniform disorder in the ECA study was 0.6%-1.1%.

Affective Disorders

The 6-month prevalence of any affective disorder in the first three ECA sites studied ranged from 4.6%-6.5%. The life-time prevalence of any affective disorder in the ECA study ranged from 6.1%-9.5%.

Depression

Numerous studies have shown that, at any one time, between 9% and 20% of the U.S. population have depressive symptoms. The figures are slightly higher among females (11%-24%) than men (6%-16%).

The ECA study of 3 sites revealed a 6-month prevalence of major depressive episode without bereavement of 1.3%-2.2% among men and 3.0%-4.6% among women for a total 6-month prevalence of 2.2%-3.5%.

The lifetime prevalence of a major depressive episode among males in the ECA three-site study was 2.3%-4.4%, and among females, 4.9%-8.7%.

Bipolar Disorder

(Bipolar disorder is a major depressive disorder accompanied by manic episodes.)

The 6-month prevalence of bipolar disorder in the ECA study of three sites ranged from 0.4-0.8 per 100, with no variation between the sexes. The lifetime risk of bipolar disorder appears to be 0.6 per 100.

Anxiety Disorders

A 1975 survey in New Haven, Connecticut, showed that the current prevalence of any anxiety disorder was 4.3%.

The 1982 ECA study of 3 community sites recorded 6-month prevalence rates of 0.6%-1.0% for panic disorder, 1.3%-2.0% for obsessive-compulsive disorder, and 2.7%-5.8% for agoraphobia.

The 6-month prevalence of phobia varied in the three ECA sites from 5.4% to 5.9% to 13.4%. Lifetime prevalence of phobia also varied according to the site studied, from 7.8% to 9.4% to 23.3%.

Among the specific phobias studied in the ECA survey agoraphobia, the fear of leaving familiar surroundings, was the most common with a 6-month prevalence of 2.7% to 5.8%. Social phobia, the irrational fear of humiliation in certain social situations, was found in 12% to 22% of persons at two of the ECA sites.

Estimates of the prevalence of post-traumatic stress disorder related to a specific stressful event vary according to the definition of the syndrome, methods of ascertainment and nature of the stressful event. It has been estimated that 7% of Vietnam veterans experienced a major depressive syndrome, and that over 26% reported psychiatric symptoms.

Antisocial Personality Disorder

Data from 3 sites in the ECA study show a 6-month prevalence of antisocial personality disorder of 0.6%-1.3% of those surveyed. The lifetime prevalence of antisocial personality disorder was 2.1%-3.3% of persons at those sites.

The prevalence of antisocial behavior may be increasing, according to a Wisconsin cohort study in which the arrest rate increased from 2.8% of those born in 1942, to 4.5% for those born in 1949, to 8.8% for those born in 1955.

Cognitive Impairment

The 6-month prevalence of severe cognitive impairment at three ECA sites ranged from 1.0%-1.3% of the surveyed population, with little difference noted between the sexes. The lifetime prevalence of severe cognitive impairment was also 1.0%-1.3%.

Suicide

Provisional data for 1984 list suicide as the eighth leading cause of death for all ages in the U.S., with 29,060 deaths, for a crude rate of 12.3 suicide deaths per 100,000 population and an age-adjusted rate of 11.6 per 100,000.

Among persons 15-34 years of age, suicide was the second leading cause of death in 1984 in the U.S.

The United States ranked tenth out of 18 industrialized countries with a suicide rate in 1978 of 12.5 (per 100,000). Austria was highest with a suicide rate of 24.8 per 100,000, and Spain had the lowest rate of 4.1 per 100,000.

From 1960-61 to 1982-83 the suicide death rate for black males increased 32.3%, compared to an increase of 9% for all races and sexes.

Childhood Mental Disorders

Infantile Autism. The prevalence of infantile autism is 4-5 per 10,000 population with a 2:1 male predominance. The disorder persists into adulthood, with a large proportion of affected individuals having evidence of brain damage (mental retardation, seizure disorder). The cause or causes are unknown.

Mental Retardation. 25% of mental retardation cases are biomedically (genetic-inutero) caused. Seventy percent are environmentally or psychosocially derived. The rest are attributed to multifactorial causes—combinations of biomedical and environmental, or other.

The prevalence of severe mental retardation (IQ lower than 60) is approximately 3-4 per 1,000.

Substance Abuse. By high school age, 33% of students have used marijuana, 15% more than 10 times, and 7% more than 60 times. Abuse of amphetamines, barbituates, narcotics, cocaine, psychedelics and inhalants occurs in 2%-10% of New York State high school students.

Risk Factor Prevalence

Demographic Risk Factors—Mental Illness, General

Sex. In the ECA study, a definite male predominance was noted for antisocial personality (3.9%-4.9% of males, compared to 0.5%-1.2% of females) and alcohol abuse/dependence (19.1%-28.9% of males, compared to 4.2%-4.8% of females).

A definite female predominance was noted in the ECA study for major depressive episode (4.9%-8.7% of females, compared to 2.3%-4.4% of males), agoraphobia (5.3%-12.5% of females; 1.5%-5.2% of males) and simple phobia (8.5%-25.9% of females; 3.8%-14.5% of males).

The ECA study also listed a probable male predominance for drug abuse/dependence and a probable female predominance for dysthymia, somatization disorder, panic disorder, obsessive-compulsive disorder and schizophrenia. No sex predominance was noted for manic episode or cognitive impairment.

Age. According to ECA data averaged from three sites, 35.3% of 18-24 year olds have had any of the DSM-III mental disorders, compared to 39.9% of 25-44 year olds, 27.9% of 45-64 year olds and 21.3% of those 65 and older.

The ECA data showed that drug abuse/dependence and schizophreniform disorder are more common among 18-24 year olds than any other age group, that cognitive impairment is found most frequently among those 65 and older, and that schizophrenia, panic, obsessive-compulsive, major depressive episode and antisocial personality are most common among those 25-44 years of age.

Race. Slight racial differences were noted in lifetime prevalence for some mental disorders, with blacks more likely than whites to have simple phobia, agoraphobia and cognitive impairment in 1 or more of the 3 sites surveyed by the ECA program.

Education. Data from the ECA program indicate that college graduates have a lower lifetime prevalence of cognitive impairment, simple phobia, agoraphobia, schizophrenia, schizophreniform disorder, alcohol abuse and dependence and somatization disorder than do others.

Urbanization. Inner city areas are associated with higher lifetime prevalence rates of drug abuse/dependence, alcohol abuse/dependence, antisocial personality, schizophrenia and cognitive impairment than rural areas.

Demographic Risk Factors—Mental Illness, Specific

Substance Abuse/Dependence. In the ECA study, alcohol abuse/dependence was higher among males (8.2%-10.4%) than females (4.5%-5.7%). Drug abuse/dependence was also higher among males (2.5-3.0%) than females (1.2%-1.6%).

Current drug abuse/dependence in the ECA study at three sites was more common among men (2.5%-3.0%) than women (1.2%-1.6%). Alcohol abuse/dependence was also more common among men (8.2%-10.4%) than women (1.0%-1.9%).

The lifetime prevalence of drug abuse/dependence is most common among persons 18-24 years old and is rare in those over 44 years, according to figures from the ECA study. The same study showed that the lifetime prevalence of alcohol abuse/dependence is similar among age groups up to age 65. In that study, 8.1%-17.0% of 18-24 year olds had alcohol abuse/dependence disorder, compared to 14.8%-21.0% of those 25-44 years of age, 8.8%-15.8% of those 45-64, and 4.1%-8.3% of those over 65 years.

Schizophrenia

Schizophrenia occurs in about 8% of siblings and 12% of offspring of schizophrenics, compared to about 1% of the general population. Concordance rates for schizophrenia are about 50% among monozygotic twins and 17% for dizygotic twins. Adoption studies have shown a higher risk for schizophrenia among those related to schizophrenics biologically rather than by adoption.

Schizophrenia usually manifests itself during ages 15-45 years, with males having a slightly earlier age of onset than females. However, overall rates of schizophrenia are about equal among males and females.

There is no apparent association between race and schizophrenia.

Affective Disorders

The 6-month prevalence of any affective disorder in three ECA study sites ranged from 2.7%-4.6% for men and from 4.6%-6.5% for women. Affective disorders appeared most commonly among those ages 25-44.

Depression. In the ECA study the lifetime prevalence of major depressive episode was slightly more common among non-Blacks (3.8%-6.8%) than among Blacks (3.7%-5.7%). When socioeconomic class is taken into account, there is no difference in rates of depression among Blacks and whites.

A review of the literature showed that the point prevalence of nonbipolar depression (major depression in the absence of manic episodes) is 3% for men and 4%-9% for women. The lifetime risk of nonbipolar depression is 8%-12% for men and 20%-26% for women, according to a review of the literature.

The median age of onset of depression seems to be the mid-20's. In the National Institute of Mental Health's Collaborative Study of the Psychobiology of Depression, 61% of patients were under 40 years of age.

Rates of depressive symptoms are significantly higher among persons of lower socioeconomic status than in persons of higher social class.

Bipolar Disorder. Bipolar depressive disorder occurs equally in males and females with onset in late adolescence. The frequency of recurrence of manic or depressive episodes increases with age.

Bipolar depressive disorder is more common among monozygotic twins (0.67 concordance) than among dizygotic twins (0.20 concordance).

Bipolar disorder is more prevalent in those of high socioeconomic, occupational and educational levels.

Anxiety Disorders

A family study has shown that the lifetime risk of panic disorder among first-degree relatives of those with panic disorder was nearly 25%. Familial patterns for other anxiety disorders are less distinct. No risk factors have been consistently associated with the development of the anxiety disorders.

Agoraphobia is about twice as common among females as males according to results of the ECA study. Agoraphobia is slightly more common among Blacks (4.4%-13.4% lifetime prevalence) than to non-Blacks (3.4%-7.2%).

Antisocial Personality

The ECA study at three sites showed a male predominance in the lifetime prevalence of antisocial personality disorder with 3.9%-4.9% of males, compared to 0.5%-1.2% of females, having had the disorder. Antisocial personality disorder is most common among the 25-44 year age group.

Cognitive Impairment

The ECA study in three sites showed that the lifetime prevalence of cognitive impairment is 1% or less up to age 65, but is about 5% for those 65 and older. There is no sex predominance in prevalence. However, the lifetime prevalence of cognitive impairment in Blacks was 1.8%-2.2% compared to 0.7%-1.3% among non-Blacks.

Suicide

Of the 28,295 suicide deaths in 1983 in the U.S., 71.0% occurred to white males, 21.4% to white females, 6.0% to all other males, and 1.6% to all other females.

The age-adjusted suicide death rate (per 100,000 population) in 1983 was 11.4 overall, 18.2 for all males, 5.2 for all females, 19.3 for white males, 10.5 for Black males, 5.6 for white females and 2.1 for Black females.

The 1983 suicide death rate (per 100,000 population) increased with age: 12 for those 15-24, 15 for those 25-44, to 16 for those 45-64, 18 for those 65-74, to a peak of 22 for those 75-84 years old.

Suicide attempts are about eight times more common than suicide completions, but only 10%-20% of those who attempt subsequently commit suicide. Whereas over 75% of those who commit suicide are male, 60% to 70% of those who attempt suicide are female. Approximately 50% of those who attempt suicide are under 30 years of age, but 44% of those who commit suicide are over 44 years of age.

Intervention Data

Mental Health Services Availability, Utilization

From 1970 to 1982, the number of state and county mental hospitals declined from 310 to 277, the number of private psychiatric hospitals increased from 150 to 211, and the number of nonfederal general hospitals with separate psychiatric services increased from 797 to 1,531.

The number of inpatient beds of all mental health organizations per 100,000 population has decreased from 263.6 in 1970 to 108.1 in 1982. This includes a 70% decline in the number of inpatient beds in state and county mental hospitals.

The number of outpatient additions to federally funded community mental health centers increased seven-fold from 1969 to 1979, resulting in over 12 million outpatient additions in 1979.

Less than one-fifth of the individuals identified with any mental disorder in a 6-month period used any health service, including either mental health specialists or general medical physicians.

In the ECA survey, 6.0%-7.1% of adults in three sites had made a professional visit for a mental health problem in the six months prior to the survey.

Among three ECA sites studied in 1982, there was broad variation in the proportion of visits for mental health reasons that were made to general medical providers (41%, 52%, 63%), compared to mental health specialists (59%, 48%, 37%).

The ECA study showed that during the six months prior to the survey, from 15.7%-25.2% of all ambulatory visits were made for mental health reasons. During the same time period at three sites in the ECA survey, from 9%-22% of all ambulatory visits were made to mental health specialists.

Among persons with any recent mental health disorder, a higher percentage of women (16%-26%) made mental health visits than men (9%-15%). However, 60%-87% of mental health visits by men were to mental health specialists, compared to 42%-57% by women.

Individuals who had received prior inpatient psychiatric care comprised 71% of admissions to non-federal general hospital psychiatric services and 80% of admissions to state and county mental hospitals.

The leading diagnosis in inpatient psychiatric services in 1980 varied according to the type of hospital: schizophrenia resulted in 38% of admissions to state and county mental hospitals, affective disorders accounted for 42.9% of admissions to private psychiatric hospitals and 31.1% of admisions to the psychiatric services of non-federal general hospitals; and alcohol-related disorders resulted in 34.5% of admissions to VA hospital psychiatric services.

The overall median days of stay for admissions (excluding deaths) to state and county mental hospitals decreased from 41 days in 1970 to 23 days in 1980. The median days of stay at private psychiatric hospitals (19) and on psychiatric services of nonfederal general hospitals (12) remained stable over the years 1970-80.

Economic Impact

In 1981, total expenditures by all mental health organizations (excluding VA medical centers) were $10.7 billion or $46.94 per capita civilian population. State and county mental hospitals accounted for 42.1% of total expenditures, followed by non-federal general hospital psychiatric services (19%), free-standing psychiatric outpatient clinics (14.5%), private psychiatric hospitals (10.4%) and all others (14%).

The direct costs of mental health care in the United States were estimated to be between $17.2 billion and $19.9 billion in 1980. This represents about 7.4% of all health care expenditures in 1980 and 0.65% of the gross national product (GNP).