asdAbnormal Behavior- Patterns of emotion, thought, and action considered pathological for one or more of these reasons: statistical infrequency, disability or dysfunction, personal distress, or violation of norms.

Medical Model- Perspective that assumes abnormal behaviors reflect mental or physical illness.

Psychiatry- The specialized branch of medicine dealing with the diagnosis, treatment, and prevention of mental disorders.

Diagnostic and Statistical Manual of Mental Disorders (DSM-IV)- A classification system, developed by the American Psychiatric Association, used to describe abnormal behaviors; the IV indicates it is in its fourth revision.

Neurosis- A term used in early versions of the DSM to describe mental disorders related to anxiety.

Psychosis- Serious mental disorders characterized by loss of contact with reality and extreme mental disruption. Since daily functioning is often impaired, psychotic individuals are more likely to need hospitalization.

Insanity- A legal term for people with a mental disorder that implies a lack of responsibility for their behavior and an inability to manage their affairs.

Anxiety Disorders- Type of abnormal behavior characterized by unrealistic, irrational fear.

Generalized Anxiety Disorder- Type of anxiety disorder characterized by chronic, uncontrollable, and excessive worry. The anxiety is not focused on any particular object or situation.

Panic Disorder- Type of anxiety disorder characterized by sudden and inexplicable attacks of intense fear. Symptoms include difficulty breathing, heart palpitations, dizziness, trembling, terror, and feelings of impending doom.

Phobia- Type of anxiety disorder characterized by intense, irrational fear and avoidance of a specific object or situation.

Obsessive-Compulsive Disorder (OCD)- Type of anxiety disorder characterized by intrusive thoughts (obsessions) and urges to perform repetitive, ritualistic behaviors (compulsions).

Posttraumatic Stress Disorder (PTSD)- Type of anxiety disorder following exposure to a life threatening or other extreme event that evoked great horror or helplessness; it is characterized by flashbacks, nightmares, and impaired functioning.

Bipolar Disorder- A diagnostic term in DSM-IV for individuals who experience episodes of mania or of both mania and depression. Excessive and unreasonable elation and hyperactivity characterize manic episodes.

Schizophrenia- Group of psychotic disorders involving major disturbances in perception, language, thought, emotion, and behavior. The individual withdraws from people and reality, often into a fantasy life of delusions and hallucinations.

Hallucinations- Sensory perceptions that occur without an external stimulus.

Dopamine Hypothesis- A theory suggesting that schizophrenia is caused by an overativity of dopamine neurons in a specific region of the brain.

Dissociative Identity Disorder (DID)- A dissociative disorder characterized by the presence of two or more distinct personality systems within the same individual; previously known as multiple personality disorder.

Dissociative Disorder- Stress-related disorder characterized by amnesia, fugue, or multiple personality. In all cases, though, the person is trying to escape from the memory of a painful experience.

Personality Disorders- A DSM-IV category that describes individuals with inflexible, maladaptive personality traits. The best known type is the antisocial personality.

Antisocial Personality- Personality disorder characterized by egocentrism, lack of conscience, impulsive behavior, and charisma.

Substance-Related Disorders- Problem use of drugs, such as alcohol, barbiturates, and amphetamines, that affects mental functioning.

Comorbidity- The co-occurrence of two or more disorders in the same person at the same time, as when a person suffers both depression and alcoholism.