A mental disorder or mental illness is a psychological or behavioral pattern that is generally associated with distress or disability, which is not considered part of normal development or the person’s culture. Such disorders are defined by a combination of affective, behavioral, cognitive or perceptual components, which may be associated with particular functions or regions of the brain or nervous system, often in a social context. The recognition and understanding of mental health conditions have changed over time and across cultures, and there are still variations in definition, assessment and classification, although standard guideline criteria are widely used. Over a third of people in most countries report problems at some time in their life which meet criteria for diagnosis of one or more of the common types of mental disorder.

The causes are often explained in terms of a diathesis-stress model or biopsychosocial model, incorporating findings from genetics, sociology, child development, biopsychiatry, clinical psychology and other fields. Services are based in psychiatric hospitals or in the community. Diagnoses or assessments are made by psychiatrists, clinical psychologists and sometimes psychiatric social workers using various methods, often relying on observation and questioning in interviews. Clinical treatments are provided by various mental health professionals. Psychotherapy and psychiatric medication are two major treatment options, as are social interventions, peer support and self-help. There may, in a minority of cases, be involuntary detention where legislation allows, typically if a person is assessed as presenting a significant risk to themselves or others due to a mental disorder; involuntary treatment may require additional evidence that a person lacks the capacity to give or withhold informed consent. Stigma and discrimination can add to the suffering and disability associated with mental disorders (or with being diagnosed or judged as having a mental disorder), leading to various social movements attempting to increase understanding and challenge social exclusion.

Adjustment Disorders

This classification of mental disorders is related to an identifiable source of stress that causes significant emotional and behavioral symptoms. The DSM-IV diagnostic criteria include:

(1) Distress that is marked and excessive for what would be expected from the stressor and
(2) Creates significant impairment in school, work or social environments.

In addition to these requirements, the symptoms must occur within three months of exposure to the stressor, the symptoms must not meet the criteria for an Axis I or Axis II disorder, the symptoms must not be related to bereavement and the symptoms must not last for longer than six months after exposure to the stressor.

Anxiety Disorders

Anxiety disorders are those that are characterized by excessive and abnormal fear, worry and anxiety. In one recent survey published in the Archives of General Psychology1, it was estimated that as many as 18% of American adults suffer from at least one anxiety disorder.

Types of anxiety disorders include:

  •     Generalized anxiety disorder
  •     Agoraphobia
  •     Social anxiety disorder
  •     Phobias
  •     Panic disorder
  •     Post-traumatic stress disorder
  •     Separation anxiety

Cognitive Disorders

These psychological disorders are those that involve cognitive abilities such as memory, problem solving and perception. Some anxiety disorder, mood disorders and psychotic disorders are classified as cognitive disorders. Types of cognitive disorders include:

  •     Alzheimer’s disease
  •     Delirium
  •     Dementia
  •     Amnesia

Developmental Disorders

Developmental disorders, also referred to as childhood disorders, are those that are typically diagnosed during infancy, childhood or adolescence. These psychological disorders include:

  •     Mental retardation
  •     Learning disabilities
  •     Communication disorders
  •     Autism
  •     Attention-deficit hyperactivity disorder
  •     Conduct disorder
  •     Oppositional defiant disorder

Dissociative Disorders

Dissociative disorders are psychological disorders that involve a dissociation or interruption in aspects of consciousness, including identity and memory. Dissociative disorders include:

  •     Dissociative disorder (formerly known as multiple personality disorder
  •     Dissociative fugue
  •     Dissociative identity disorder
  •     Depersonalization disorder

Eating Disorders

Eating disorders are characterized by obsessive concerns with weight and disruptive eating patterns that negatively impact physical and mental health. Types of eating disorders include:

  •     Anorexia nervosa
  •     Bulimia nervosa
  •     Rumination disorder

Factitious Disorders

These psychological disorders are those in which an individual acts as if he or she has an illness, often be deliberately faking or exaggerating symptoms or even self-inflicting damage to the body. Types of factitious disorders include:

  •     Munchausen syndrome
  •     Munchausen syndrome by proxy
  •     Ganser syndrome

Impulse-Control Disorders

Impulse-control disorders are those that involve an inability to control impulses, resulting in harm to oneself or others. Types of impulse-control disorders include:

  •     Kleptomania (stealing)
  •     Pyromania (fire-starting)
  •     Trichotillomania (hair-pulling)
  •     Pathological gambling
  •     Intermittent explosive disorder
  •     Dermatillomania (skin-picking)

Mental Disorders Due to a General Medical Condition

This type of psychological disorder is caused by an underlying medical condition. Medical conditions can cause psychological symptoms such as catatonia and personality changes. Examples of mental disorders due to a general medical condition include:

  •     Psychotic disorder due to epilepsy
  •     Depression caused by diabetes
  •     AIDS related psychosis
  •     Personality changes due to brain damage

Mood Disorders

Mood disorder is a term given to a group of mental disorders that are all characterized by changes in mood. Examples of mood disorders include:

  •     Bipolar disorder
  •     Major depressive disorder
  •     Cyclothymic disorder