6 minute read

Mental Illness

Overview, Causes and symptoms, Diagnosis and treatment

The term used to describe a disorder or condition that negatively affect cognition (thought), behavior, and/or affect (mood) to such a point where it causes a significant amount of distress and functional impairment for a prolonged period of time.

Many mental hospitals are modernizing their treatment methods, including this one with patients participating in dance therapy. (Photo Researchers, Inc. Reproduced with permission.)


Mental illness is a serious public health problem. According to the World Health Organization and the Harvard School of Public Health, mental illness accounts for nearly 11 percent of total worldwide disease burden. (Disease burden is determined by the calculation of DALYs, or disability-adjusted life years. The DALY statistic measures lost years of healthy life from death or disability due to a disease.) In countries that are considered "established market economies" (i.e., United States, Great Britain), mental illness is second only to heart disease as the most disabling disease category. Unipolar major depression was determined to be the second leading source of disease burden (after ischemic heart disease) in established market economies, and the fourth leading cause of disease burden worldwide.

In its Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), a reference standard for mental health professionals, the American Psychiatric Association distinguishes 16 different subtypes (or categories) of mental illness. These include:

  • Disorders usually first diagnosed in infancy childhood, or adolescence. These include learning and developmental disorders, mental retardation, and attention-deficit hyperactivity disorder.
  • Delirium, dementia, amnestia, and other cognitive disorders. These include dementia related to Alzheimer's disease, head injury, and central nervous system infection; and substance-induced delirium.
  • Mental disorders due to a general medical condition. Medical/mental conditions that are not classified in other areas of the DSM-IV are found in this category.
  • Substance-related disorders. Disorders related to alcohol and drug use, abuse, dependence, and withdrawal are included in this category.
  • Schizophrenia and other psychotic disorders. These include the schizoid disorders (schizophrenia, schizophreniform, and schizoaffective disorder), delusional disorder, and psychotic disorders.
  • Mood disorders. Depressive disorders (major, dysthymic) and bipolar disorders are classified as mood disorders.
  • Anxiety disorders. This classification includes panic disorder, agoraphobia, social phobia, obsessive-compulsive disorder, posttraumatic stress disorder, and generalized anxiety disorders, all disorders in which a certain situation or place triggers excessive fear and/or panic symptoms (i.e., dizziness, racing heart).
  • Somatoform disorders. Somatoform disorders involve clinically significant physical symptoms that cannot be explained by a medical condition. Somatization disorder, conversion disorder, pain disorder, hypochondriasis, and body dysmorphic disorder.
  • Factitious disorders. These are disorders in which the individual creates and complains of symptoms of a non-existent illness in order to assume the role of a patient (or sick role).
  • Dissociative disorders. These disorders involve a change in memory, identity, and/or consciousness. They include dissociative amnesia, dissociative fugue, dissociative identity disorder, and depersonalization disorder.
  • Sexual and gender identity disorders. Disorders of sexual desire, arousal, performance, and pain are included here, as is gender identity disorder. It should be noted that the inclusion of gender identity disorder as a mental illness in the DSM-IV has been a point of some contention among mental health professionals.
  • Eating disorders. Anorexia and bulimia are both eating disorders.
  • Sleep disorders. Insomnia, narcolepsy, hypersomnia, and parasomnias (nightmares and sleepwalking) are all considered sleep disorders.
  • Impulse-control disorders not elsewhere classified. Includes kleptomania and pyromania.
  • Adjustment disorders. Adjustment disorders involve an excessive emotional or behavioral reaction to a stressful event.
  • Personality disorders. These are maladjustments of personality, including paranoid, schizoid, schizotypal, antisocial, borderline, histrionic, narcissistic, avoidant, dependent, and obsessive-compulsive personality disorder (not to be confused with the anxiety disorder OCD).

Causes and symptoms

The causes of mental illness are not completely understood, but organic, genetic (hereditary), familial, traumatic life events, and social factors all may play a part in triggering mental illness. Frequently, it is a combination and interrelationship of several of these factors. For example, schizophrenia is caused by genetically determined abnormalities in the structure and chemistry of the brain, but the course and severity of the disease can be influenced by social factors such as environmental stress and the absence of a family or peer support system.

In some cases, mental illness is primarily a byproduct of a disease or general medical condition. For example, central nervous system infections that can occur in advanced AIDS can cause dementia. Depending on their location and severity, neurological conditions such as traumatic brain injury, tumor, or infarct (areas of tissue death as a result of loss of blood supply) can also cause various symptoms of mental illness.

Individuals dealing with traumatic life events (e.g., death of a close friend, experiencing a natural disaster, witnessing a brutal crime) may experience psychological distress and difficulty dealing with day-today tasks. Because these mental health problems tend to be of a temporary nature, they aren't termed mental illness. It is important to remember that prompt and proper treatment of these issues in the form of counseling or other psychological interventions is critical, as they have the potential to progress into a long-term mental disorder or illness.

Diagnosis and treatment

Patients with symptoms of mental illness should undergo a thorough physical examination and patient history to rule out an organic or structural cause for the illness. If a neurological cause for the disorder is suspected, further diagnostic tests (e.g., CT scan, MRI, PET scan, neuropsychological assessments) are typically required. If a disorder with no organic cause is suspected, a psychologist or other mental healthcare professional will conduct a patient interview and administer one or more psychological assessments (also called clinical inventories, scales, or tests).

Counseling is typically a front-line treatment for mental illness. A number of counseling or talk therapy approaches exist, including psychotherapy, cognitive therapy, behavioral therapy, and group therapy. These are sometimes used in conjunction with alternative therapy approaches such as art or music therapy that use the creative process to promote patient self-discovery and awareness. A number of mental healthcare professionals are involved in the treatment of mental illness, including licensed counselors and therapists, social workers, nurses, psychologists, and psychiatrists.

Psychoactive medication is prescribed for symptom relief in patients with organic and non-organic mental illness. For mental illnesses that are considered biological in nature, such as bipolar disorder or schizophrenia, pharmaceutical therapy is considered a primary treatment approach. In other cases, such as in personality disorder or dissociative disorder, psychoactive medications are usually considered a secondary, or companion treatment to psychotherapy.

Many individuals suffering from mental illness choose to treat their illness through regular attendance in self-help groups, where they can seek advice and counsel from others in similar circumstances. Some of the most popular self-help organizations (i.e., Alcoholics Anonymous), are as, if not more, effective than traditional doctor/patient therapy for many individuals.

In some cases, effectively treating mental illness requires hospitalization of the patient. This hospitalization, also known as inpatient treatment, is usually employed in situations where a controlled therapeutic environment is critical for the patient's recovery (e.g., rehabilitation treatment for alcoholism or other drug addictions), or when there is a risk that the patient may harm himself (suicide) or others. One popular variation of the inpatient treatment program, known as milieu therapy, focuses on providing the patient with opportunities to gain self-confidence and interact with peers in a positive way. Activities that encourage self-discovery and empowerment such as art, music, dance, and writing are important components of this approach.

Further Reading

American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders 4th ed. Washington, DC: American Psychiatric Press, Inc., 1994.

World Health Organization, World Bank, and Harvard University. Murray CL, Lopez AD, eds. The Global Burden of Disease: A comprehensive assessment of mortality and disability from diseases, injuries, and risk factors in 1990 and projected to 2020. Cambridge, MA: Harvard University Press, 1996.

Satcher, David. Mental Health: A Report of the Surgeon General. Washington, DC: Government Printing Office, 1999. [available online at www.surgeongeneral.gov]

Further Information

National Institute of Mental Health (NIMH). 6001 Executive Boulevard, Rm. 8184, MSC 9663, Bethesda, MD, USA. 20892-9663, fax: 301-443-4279, 301-443-4513. Email: nimhinfo@nih.gov. http://www.nimh.nih.gov.

Additional topics

Psychology EncyclopediaDiseases, Disorders & Mental Conditions