The 2000 version of the American Psychiatric Association’s diagnostic manual, the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (termed DSM -IV for short), contains nearly 400 mental disorders, distributed across seventeen broad categories. These categories include childhood disorders, schizophrenia and psychotic disorders, mood disorders, substance-related disorders, anxiety disorders, eating disorders, sleep disorders, personality disorders, sexual- and gender-identity disorders, and impulse-control disorders. The number of mental disorders has ballooned from the first DSM edition in 1952 to the present, reflecting an increased “splitting” of broad mental illness categories into narrower ones.
DSM -IV describes individuals along five axes, or dimensions of functioning, the first two of which focus on what is conventionally regarded as mental illness. By providing users with a multiaxial formulation, DSM -IV aims to paint a reasonably comprehensive picture of each individual.
Axis I lists most major mental disorders, such as schizophrenia, mood disorders, and anxiety disorders. In general, researchers view these disorders as acute problems that are superimposed on individuals’ preexisting functioning.
Axis II lists personality disorders and mental retardation, which ostensibly differ from Axis I disorders in their greater persistence over time. Personality disorders are extremes of personality traits, such as impulsivity, dependency, and anxiety, that are inflexible, maladaptive, or both. Mental retardation is characterized by an IQ (intelligence quotient) of approximately 70 or below, severe deficits in adaptive functioning (e.g., inability to cook or dress oneself), and onset prior to adulthood.
Axis III lists medical conditions that can be relevant to individuals’ psychological functioning. Medical conditions can adversely affect the prognosis of many mental disorders and mimic the symptoms of many others. For example, hypothyroidism and stroke can produce the full clinical picture of major depression, a condition characterized by extreme sadness and loss of pleasure, along with such features as extreme guilt, sleeping and eating difficulties, and suicidal thinking.
Axis IV lists recent life stressors, such as death of a relationship partner or friend, and environmental problems, such as housing difficulties, extreme poverty, or inadequate access to mental health services. These psychological factors can precipitate or maintain mental illnesses. For example, research indicates that certain negative life events, especially those involving losses of loved ones, can trigger major depression in predisposed individuals. Evidence also suggests that schizophrenia, a condition marked by unusual thinking, delusions (fixed false beliefs), and hallucinations (perceptions occurring in the absence of any stimulus), can be triggered in some predisposed individuals by the stresses associated with poverty. Nevertheless, evidence suggests that causality also operates in the reverse direction because, for example, the deteriorating job skills associated with schizophrenia can lead to poverty.
Axis V describes the individual’s overall level of daily functioning. The inclusion of this axis acknowledges that people with the same psychiatric disorder differ markedly in their levels of adaptation to the environment. For example, some people with major depression are almost constantly bedridden, suicidal, or both, whereas others manage to perform surprisingly well in their occupational and family lives despite intense psychological pain.
Theoreticians have long struggled with the question of what, if anything, all disorders of psychological functioning have in common. Although they have proposed numerous definitions of psychiatric disorder, all of these definitions have their shortcomings.
A subjective distress model posits that all mental disorders are marked by inner tUniformoil. Although many mental disorders, such as panic disorder (a condition marked by sudden surges of intense anxiety), are associated with subjective distress, some others, such as antisocial personality disorder (a condition marked by a long-standing history of illegal and irresponsible behavior) are associated with minimal subjective distress.
A statistical model posits that mental disorders are marked by statistical rarity. Although many mental disorders, such as infantile autism (a condition originating in infancy that is associated with serious deficits in language, social bonding, and imagination), are relatively rare in the population, others, such as major depression, are fairly common.
An evolutionary model posits that all mental disorders generate biological disadvantage, such as reduced life span or reduced ability to reproduce. Although some mental disorders, such as major depression, are associated with increased rates of suicide and therefore clear-cut biological disadvantage, others, such as specific phobia (an intense and irrational fear of an object, place, or situation), are not associated with any apparent reduction in lifespan or reproductive capacity.
In the 1990s Jerome Wakefield attempted to remedy these shortcomings by proposing that all mental disorders are harmful dysfunctions. According to Wakefield, all mental disorders (1) produce undesirable consequences for the affected individual, society, or both (harm); and (2) are characterized by the failure of a psychological system to perform its evolved function (dysfunction). For example, according to Wakefield, paranoia (“delusional disorder” in DSM-IV) is a mental disorder because (1) people with paranoia frequently experience marked distress, and (2) paranoia reflects a failure of the human threat system to operate properly. Specifically, in paranoia the threat detection system either reacts to nonexistent dangers or overreacts to mild ones. Yet the harmful dysfunction formulation has its limitations. In particular, some conditions, such as anxiety disorders, do not appear to stem from dysfunctions. Instead, in most cases these conditions seem to result from evolved systems reacting in adaptive ways to subjectively perceived threats.
In light of the problems with previous attempts to define disorder, some authors have proposed that psychiatric disorders are best conceptualized in terms of a family resemblance model. Just as brothers and sisters within a large family tend to look similar but do not share any single facial characteristic, mental disorders typically share a loosely covarying set of features. These features include subjective distress, statistical rarity, biological dysfunction, impairment, societal disapproval, irrationality, and loss of control over one’s behavior. From this perspective, there is no “bright line” demarcating abnormality from normality, but rather a constellation of partly overlapping attributes that set most psychiatric disorders apart from healthy functioning.
The mental illness concept has long had its harsh critics. Advocates of labeling theory, such as Thomas Szasz (b. 1920), have argued that diagnoses of mental illness are merely pejorative names that society attaches to behavior that it finds objectionable. In a 1961 book Szasz referred famously to mental illness as a myth, contending that what the mental health profession calls psychological disorders are actually “problems in living,” that is, difficulties in adjusting one’s behavior to societal demands. Many labeling theorists further contend that psychiatric diagnoses are culturally relative, because the behaviors that societies deem abnormal vary markedly across place and time.
Labeling theory has served a valuable function by reminding psychologists and psychiatrists that diagnoses are readily abused. Many nonscientific “diagnoses” in the popular psychology literature, such as sexual addiction, codependency, and road-rage disorder, are scant more than descriptive labels for undesirable behaviors. These labels yield little new information. For example, labeling an aggressive driver with road-rage disorder informs us only that this person frequently loses his or her temper while driving, a fact of which we were already aware.
Nevertheless, labeling theory’s critique of psychiatric diagnostic systems and the concept of mental illness falls short on at least three grounds. First, many devalued behaviors, such as laziness, slovenliness, rudeness, and racism, are not mental disorders. Therefore, there is more to psychiatric disorder than social undesirability.
Second, many labeling theorists have overstated the cultural relativity of mental disorders. Admittedly, some mental disorders are specific to certain cultures. For example, koro, a condition characterized by a pathological fear that one’s genitals are disappearing, is localized largely to parts of Southeast Asia. Nevertheless, many major psychological disorders appear to be present across most, if not all, cultures. In 1976 Jane Murphy conducted a significant study of two societies that had experienced essentially no contact with Euro-American culture—a group of Yorubas in Nigeria and a group of Eskimos near the Bering Strait. These cultures had terms for disorders that were strikingly similar to several Euro-American disorders, including alcoholism, schizophrenia, and psychopathic personality, a condition marked by dishonesty, callousness, guiltlessness, and lack of empathy.
Third, many psychological diagnoses do more than describe already known behaviors. As Eli Robins and Samuel Guze observed in a classic 1970 article, valid psychological diagnoses provide us with novel information. For example, if we accurately diagnose an individual with bipolar disorder, formerly known as manic depression, we will learn several things about that individual that we did not know previously. Among other things, we will learn that this individual (1) experiences relatively sudden episodes of both mania (a condition marked by dramatically elated mood, energy, and self-esteem, along with poor judgment and impulsivity) and depression, typically punctuated by periods of essentially normal functioning; (2) is more likely than nonaffected individuals to have one or more biological relatives with mood disorders; (3) is at heightened risk for other psychological difficulties, including substance abuse and suicide; and (4) will probably respond positively to certain medications, such as lithium carbonate and antiseizure agents.
Several large survey studies conducted in the 1980s, 1990s, and early twenty-first century have yielded valuable knowledge regarding the prevalence of major mental disorders in the general population. A 2005 study by Ronald Kessler and his colleagues revealed that between 25 percent and 30 percent of Americans suffer from anxiety disorders such as phobias, about 20 percent suffer from mood disorders such as depression and bipolar disorder, and about 15 percent suffer from substance-abuse disorders such as alcoholism. A surprisingly large proportion of Americans, perhaps 25 percent, also suffer from impulse-control disorders such as kleptomania (marked by recurrent stealing) and pathological gambling. On a lifetime basis, the most prevalent single disorder appears to be major depression, which afflicts about 17 percent of Americans at some point in their lives.
Survey studies also reveal important gender differences in the prevalence of some mental disorders. For example, in most populations major depression is about twice as common in women than in men. Antisocial personality disorder, in contrast, is about three times as common in men as in women. The reasons for these gender differences are unknown, but remain an active area of research investigation.
Race differences in the prevalence of psychopathology tend to be less pronounced than gender differences, although there are notable exceptions. For example, post-traumatic stress disorder, a condition marked by severe anxiety and avoidance reactions following a traumatic event (e.g., a rape, shooting, or motor vehicle accident), appears to be more prevalent in African Americans than in whites, perhaps because individuals in poor, inner-city areas, including many African Americans, often witness and experience traumatic events. Alcoholism is more prevalent in Native Americans than in other individuals, probably for a mixture of genetic and environmental reasons, the latter including poverty and alienation from the broader American society.
The past several centuries have witnessed a variety of approaches to the etiology, or causation, of psychiatric illnesses. Etiological models of psychological disorder have shifted over time in accord with prevailing societal conceptions.
During the Middle Ages many people embraced a demonic model, which viewed mental illnesses largely as the product of evil spirits infecting the mind. Not surprisingly, exorcism was often the preferred “treatment” of the day. In succeeding centuries, conceptions of the causes of mental disorder became progressively more rooted in naturalistic as opposed to spiritual explanations.
Psychodynamic approaches, originated by Sigmund Freud (1856-1939) and his followers, place substantial emphasis on the role of early life experiences, unconscious influences, and psychological conflict in the genesis of mental disorder. For example, psychodynamic theorists might view obsessive-compulsive disorder, an anxiety disorder characterized by repeated intrusive thoughts (e.g., fears of contamination) and by unsuccessful efforts to neutralize them (e.g., frantic cleaning), as an unconscious psychological defense against deep-seated fears of loss of emotional control. These fears, in turn, may trace their roots to aversive childhood experiences, such as physical or sexual trauma. Despite their value in generating hypotheses concerning the causes of mental illness, psy-chodynamic theories have proven difficult to test.
Behavioral approaches, influenced by the work of John B. Watson (1878-1958), B. F. Skinner (1904–1990), Joseph Wolpe (1915–1997), and others, conceive of mental disorder as maladaptive learned habits. For behaviorists, atypical and disturbed behaviors are governed by the same learning processes as other behaviors. For example, behaviorists might attempt to explain a phobia of dogs in terms of an early unpleasant experience with a dog in conjunction with subsequent avoidance behavior. By avoiding dogs whenever they are within sight, the victim of a dog bite experiences short-term relief. Yet this person also forfeits the opportunity to learn that most dogs are not as dangerous as he or she fears.
Cognitive approaches, pioneered by Albert Ellis (b. 1913), Aaron Beck (b. 1921), and others, posit that psychological disorders derive from irrational patterns of thinking. Cognitive theorists emphasize that an individual’s interpretations of events, rather than events themselves, are the principal determinants of behavior. They regard unfounded beliefs about oneself, the world, and the future—such as the belief that “I must be perfect” or that “I must be liked by everyone to be a worthwhile person”—to be risk factors for depression and other disorders.
Biological approaches focus on physiological factors, such as genetic influences, early damage to the central nervous system, and hormonal abnormalities, as predisposing factors in mental illness. There is compelling evidence from twin and adoption studies—which permit researchers to disentangle the roles of genes and environ-ment—that genetic factors play a substantial role in a wide array of psychiatric disorders, including schizophrenia, mood disorders, and anxiety disorders. There is also preliminary but growing evidence that viral infections prior to birth may set the stage for subsequent schizophrenia.
The advent of sophisticated neuroimaging techniques such as PET (positive emission tomography) and fMRI (functional magnetic resonance imaging) has been a substantial boon to biological approaches, as these techniques have allowed researchers to discover which brain areas are underactive or overactive during certain tasks. For example, many individuals with schizophrenia exhibit decreased activity in their frontal lobes, which is consistent with the poor judgment, inadequate planning, and memory deficits often observed in this condition. The human genome project also promises to add to our understanding of the biological underpinnings of mental disorder, because it is permitting researchers to identify genes linked to specific psychological disorders.
Proponents of differing etiological models have often sorted themselves into highly partisan camps, separated as much by ideology as evidence. Yet, few if any of these etiological approaches are mutually exclusive. Moreover, most researchers and theorists agree that the causes of mental disorders are likely to be multifactorial, that is, produced by many variables rather than one. In some cases, these causal variables may interact. For example, several studies indicate that a genetic abnormality that affects serotonin, a chemical messenger in the brain, may combine with life stressors to trigger depression. As a consequence, the most fruitful approaches to understanding mental disorder will probably involve multidisciplinary collaborations among researchers from diverse theoretical perspectives.
SEE ALSO Alcoholism; Anxiety; Behaviorism; Cognition; Cultural Relativism; Depression, Psychological; Freud, Sigmund; Madness; Manic Depression; Mental Health; Mental Illness; Mental Retardation; Mood; Nature vs. Nurture; Neuroticism; Obsessive-Compulsive Disorder; Panic; Personality; Post-Traumatic Stress; Psychopathology; Psychotherapy; Schizophrenia; Stress
American Psychiatric Association. 2000. Diagnostic and Statistical Manual of Mental Disorders. 5th ed., text rev. Washington, DC: American Psychiatric Association.
Breslau, J., K. S. Kendler, M. Su, S. Gaxiola-Aguilar, and R. C. Kessler. 2005. Lifetime Risk and Persistence of Psychiatric Disorders across Ethnic Groups in the United States. Psychological Medicine 35: 317–327.
Gorenstein, Ethan E. 1992. The Science of Mental Illness. San Diego, CA: Academic Press.
Kendell, Robert E. 1975. The Concept of Disease and Its Implications for Psychiatry. British Journal of Psychiatry 127: 305–315.
Kessler, Ronald C., Wai T. Chui, Olga Demler, and Elaine E. Walters. 2005. Prevalence, Severity, and Comorbidity of 12-Month DSM-IV Disorders in the National Comorbidity Survey Replication. Archives of General Psychiatry 62: 617–627.
McHugh, Paul R., and Phillip R. Slavney. 1998. The Perspectives of Psychiatry. 2nd ed. Baltimore, MD: Johns Hopkins University Press.
Meehl, Paul E. 1973. Psychodiagnosis: Selected Papers. Minneapolis: University of Minnesota Press.
Murphy, Jane. 1976. Psychiatric Labeling in Cross-Cultural Perspective. Science 191: 1019–1028.
Robins, Eli, and Samuel B. Guze. 1970. Establishment of Diagnostic Validity in Psychiatric Illness: Its Application to Schizophrenia. American Journal of Psychiatry 126: 983–987.
Szasz, Thomas. 1960. The Myth of Mental Illness. American Psychologist 15: 113–118.
Wakefield, Jerome C. 1992. The Concept of Mental Disorder: On the Boundary between Biological Facts and Social Values. American Psychologist 47: 373–388.
Scott O. Lilienfeld
Genetic studies of psychiatric disorders have become an important specialty area within medical genetics. Much of the progress in the area is the result of advances in molecular genetics techniques, The Human Genome Project, developments in the neurosciences, and recent genetic findings in complex brain disorders such as Alzheimer's and Huntington's disease.
Psychiatric Disorders with Genetic Involvement
It is well accepted that many of the psychiatric disorders listed in the Diagnostic and Statistical Manual, fourth edition, have hereditary predispositions. (The DSM-IV is the official diagnostic manual for mental disorders in the United States.) In the last two decades, clinical genetic (family, twin, and adoption) studies have provided some valuable information about both the genetic and environmental aspects that lead to the development of these psychiatric disorders. More recently, a growing number of molecular genetics studies have provided more data about the genetics of the disorders. However, there has been little success in the identification of specific genes involved in the etiology of these complex disorders.
The DSM-IV includes more than 350 diagnoses and at least one third of the disorders have had one or more clinical genetic study completed. Additionally, some of the disorders have been subjected to molecular genetic studies. Several of the most frequently examined DSM-IV psychiatric disorders from a "genetic study" perspective are listed below:
- Attention Deficit Hyperactivity Disorder (ADHD)
- Bipolar Disorder
- Mental Retardation
- Obsessive-Compulsive Disorder (OCD)
- Panic Disorder
- Social Phobia
- Substance Use Disorder
- Tourette's Syndrome
Major psychiatric disorders, such as schizophrenia and bipolar disorder, have been shown in numerous studies to have significant genetic factors involved in their etiology. The effects of environment and gene-environment interactions on the expression of the disorders are thought to be important, but need more study. Several childhood onset disorders, such as mental retardation, autism, and ADHD, also have strong genetic components in their etiology. All of these disorders are considered complex and are thought to have multiple genes acting together with nongenetic factors, with each gene typically contributing only small effects.
Inheritance Patterns and Linkage Studies
Complex disorders such as schizophrenia and bipolar disorder usually do not follow classic Mendelian inheritance patterns, but they can frequently mimic a pattern of autosomal dominance with reduced penetrance. Explanatory models for these complex disorders include multifactorial inheritance (multiple genes with nongenetic components) and epistasis (few genes acting jointly). But, since the mode of inheritance is unknown, a range of analytic methods must be used to study the genetic aspects of these disorders. Linkage and allelic association studies are frequently methods used to investigate possible causal genes for complex psychiatric disorders. However, in large populations, there are likely to be several causal or susceptibility genes and nongenetic causes, as well.
Historically, the first positive linkage study to have a major impact on psychiatry was the linkage of bipolar disorder to chromosome eleven in a large Amish family. However, a later assessment of the family failed to confirm the original linkage results. A similar situation occurred with the failure to replicate the findings of an early report of linkage of schizophrenia to a region on chromosome 5 in Icelandic and British families.
As a result of these early problems, it became clear that more rigorous methodology, such as more careful clinical phenotyping, the use of more genetic markers, and new analytic techniques would be necessary if molecular approaches were to be used in finding genes involved in psychiatric disorders.
Clinical genetic (family, twin, and adoptive) studies have been attempted in a large number of psychiatric disorders. However, these studies generally provide no information about what genes are involved in the disorder. Molecular studies are necessary to begin to elucidate this data. Schizophrenia and bipolar disorder are examples of psychiatric disorders that have been studied for nearly two decades.
Schizophrenia and Bipolar Disorder
Schizophrenia is a disorder characterized by psychotic symptoms such as hallucinations, delusions, and disordered thinking, as well as deficits in emotional and social behavior. Numerous family, twin, and adoption studies have provided substantial evidence for genetic factors in the etiology of this disorder. Nongenetic factors also appear to play an important role. The risk for relatives of an individual with schizophrenia is 6.5 percent, nearly eight times the population rate of the disorder. The concordance rate for monozygotic (identical) twins is 45 percent, and for dizygotic (fraternal) twins the rate is 12 percent. The higher rate for monozygotic twins, who share all their genes, is strong evidence that genes play a role in schizophrenia.
Molecular genetic (linkage and association) studies suggest that there are multiple genes with small effects that predispose one to the disorder. In an early study, chromosome 5q was implicated, but was not replicated. Areas on chromosome 6p and 8p have been replicated in at least one follow-up study. More recently, chromosome 1 has been implicated. While no causative genes have been identified, there have been molecular studies that implicate chromosomes 1q, 3p, 5, 6p, 6q, 8p, 10p, 13q, 18p and 22q in schizophrenia. Like other multifactoral diseases, the etiology of schizophrenia involves multiple genes and gene-environment interactions.
Bipolar disorder is characterized by episodes of depression and mania, elevated or irritable mood, and symptoms such as rapid thoughts, grandiose ideas, and reckless behavior. Population, twin, and adoption studies provide evidence for the role of genetics in the etiology of bipolar disorder. First-degree relatives have about a 7 to 10 percent risk of having the disorder once one family member is diagnosed. The concordance rate for monozygotic twins is 60 to 65 percent, and for dizygotic twins the rate is 10 to 15 percent, the same as for non-twin siblings.
One of the first bipolar disorder molecular genetic studies implicated chromosone 11, but this finding was not replicated in several other studies. A similar failure to replicate occurred with the initial reports of linkage on the chromosome X. Regions on chromosome four are reported to show strong evidence of linkage to some bipolar families. Major efforts in the last few years have been focused on chromosome seven and eighteen. Some of the studies have suggested a parent-of-origin effect, with maternal transmission more common than paternal. Both linkage and association studies have implicated chromosomes 4p, 6p, 12q, 13q, 16p, 18p, 18q, 21q, and 22q in bipolar disorder. Major depressive disorder has also been studied, but the underlying genetic factors have not been identified.
Some psychiatric disorders, like Tourette's syndrome, have significant overlap (co-morbidity) with other psychiatric disorders (OCD and ADHD in the case of Tourette's). This may make the elucidation of genetic causes more difficult.
Tourette's syndrome is characterized by multiple motor tics and one or more vocal tics. It has onset before eighteen years and is one and one-half to three times more common in males. Twin, adoption, and segregation analysis studies support a genetic etiology for Tourette's syndrome. An autosomal dominant inheritance was initially suggested, but other inheritance patterns have been recently reported. There appears to be a relation with ADHD (up to 50 percent of individuals with Tourette's also have ADHD) and OCD (up to 40 percent of individuals with Tourette's have OCD). First-degree relatives are at high risk for developing tics and obsessive compulsive disorders.
Studying psychiatric disorders for genetic factors in their etiology is difficult because of the phenotype definition, co-morbidity, and multiple causal factors. The summary finding from the genetic studies to date suggest that there are multiple genes of small to moderate effect underlying the predisposition to these complex psychiatric disorders.
see also Alzheimer's Disease; Attention Deficit Hyperactivity Disorder; Complex Traits; Gene Discovery; Inheritance Patterns.
Harry H. Wright
and Ruth Abramson
Malhotra, A. K. "The Genetics of Schizophrenia." Current Opinions in Psychiatry 14, no. 1 (2001): 3-7.
Potash, J. B., and J. R. DePaulo. "Searching High and Low: A Review of the Genetics of Bipolar Disorder." Bipolar Disorders 2, no. 1 (2000): 8-26.
Roy, M. A., C. Merette, and M. Maziado. "Introduction to Psychiatric Genetics:Progress in the Search for Psychiatric Disorder Dusceptibility Genes." Canadian Journal of Psychiatry 46, no. 1 (2001): 52-60.