Psychological disorders are so widespread that, even if you never experience one in your lifetime, you will almost certainly know someone who does. Ancient humans believed that abnormal behavior is caused by supernatural forces. Up until fairly recent history, people with psychological disorders were subjected to trephination to "release" the spirit, or branded as witches. Early biological views, such as those of the Greek physician Hippocrates, suggested that psychological disorders are diseases just like physical disorders. Early psychological theories focused on the use of psychoanalytic, behavioral, cognitive, and humanistic theories to explain abnormality. Today most clinical psychologists and counselors believe in the vulnerability-stress model, which suggests that we all have some susceptibility, given sufficient stress. Biological, psychological, and environmental and sociocultural factors all play a role in the development of psychological disorders.
Judgments about what an "abnormal" behavior is are often difficult to make, can vary from culture to culture, and can change as societies develop. A current working definition for abnormal behavior is "behavior that is personally distressful, personally dysfunctional, and/or so culturally deviant that other people judge it to be inappropriate or maladaptive." The most widely used diagnostic system for classifying mental disorders in the United States is called the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). DSM-IV uses five axes (primary diagnosis, personality/developmental disorders, relevant physical conditions, severity of psychosocial stressors, and global assessment of functioning) to help clinicians understand disorders. Criminal "insanity" defense standards have shifted since the 1980s; defendants must now prove that they were not sane when they committed the crime.
In anxiety disorders, the frequency and intensity of anxiety responses are out of proportion to the situations that trigger them, and the anxiety interferes with daily life. Anxiety disorders have subjective-emotional, cognitive, physiological, and behavioral components. Phobias are strong and irrational fears of certain objects or situations. Generalized anxiety disorder is a chronic state of anxiety (called 'free-floating') that is not attached to specific situations or objects. Panic disorders involve sudden and unpredictable anxiety that is extremely intense. Obsessive-compulsive disorder involves repetitive and unwelcome thoughts, images, and impulses and repetitive behavioral responses. People who have been exposed to traumatic live events may develop posttraumatic stress disorder, whose symptoms include anxiety, "flashbacks," avoidance of reminders of the traumatic event, and "survivor guilt" in cases where others in the same situation did not survive. Biological factors including genetics, neurotransmitters, and evolutionary factors have all been implicated in the development of anxiety disorders. Psychological factors such as cognitive processes and learning also play important roles in the development of anxiety disorders. Anxiety disorders are more prevalent in women than in men, and sociocultural factors can also play a role, as indicated by the existence of various culture-bound anxiety disorders.
Somatoform disorders, such as hypochondriasis, involve physical complaints or disabilities that suggest a medical problem, but which have no known biological cause.
Dissociative disorders involve a breakdown of the normal integration of personality. These disorders include psychogenic amnesia, psychogenic fugue, and dissociative identity disorder (formerly called multiple personality disorder). According to trauma-dissociation theory, dissociative disorders develop due to response to severe stress in a person's life.
Together with anxiety disorders, mood disorders are the most prevalent psychological disorders. Depression involves emotional, cognitive, motivational, and somatic (body) symptoms. Major depression may lead people to be unable to function, while a less intense form of depression called dysthymia has less dramatic effects on personal functioning. Bipolar disorder involves both depression and periods of mania, which is a state of excited mood and behavior. Women experience higher rates of depression, but not of bipolar disorder, than men. Biological factors, including genetics and neurotransmitters, play an important role in the development of mood disorders. Low levels of neurotransmitters such as serotonin, dopamine, and norepinephrine may be particularly likely to influence the development of mood disorders. Psychological factors including personality, cognitive processes, and learning also play roles. Sociocultural factors can affect the prevalence of depressive disorders and the ways in which depression is manifested. Depression is the strongest predictor of suicide, and suicide is the leading cause of death after accidents among high school and college students. Warning signs of suicide should be taken seriously and professional help should be sought.
Schizophrenia is a psychotic disorder that involves severe disturbances in thinking, speech, perception, emotion, and behavior. DSM-IV differentiates between four major types of schizophrenia: paranoid type, disorganized type, catatonic type, and undifferentiated type. Strong evidence exists for the role of genetic factors in the development of schizophrenia. MRI studies have shown abnormalities in schizophrenics including brain atrophy (a loss of neurons in the cerebral cortex and the limbic system). Overactivity of the dopamine system may play a role in the development of schizophrenia. Psychological factors such as family dynamics, especially families with a high level of expressed emotion (criticism, hostility, and overinvolvement) may also play a role. Studies of sociocultural factors have indicated that the prevalence of schizophrenia is highest in lower socioeconomic populations. Schizophrenia appears to be relatively "culture-free," as it occurs fairly evenly worldwide.
Personality disorders are stable, ingrained, inflexible, and maladaptive ways of thinking, feeling, and behaving. The most serious of these is antisocial personality disorder, in which the person seems to lack a conscience. Antisocial personality disorder is three times as common in men as in women. Studies have focused on the role of genetics, and psychological factors such as classical conditioning and modeling, as causes of antisocial personality disorder.
Both children and the elderly are at high risk for a variety of disorders. Moreover, many childhood disorders are precursors for psychological disorders in adulthood. Childhood disorders are divided into two categories. Externalizing disorders are characterized by inattentive, disruptive, or aggressive behavior; attention deficit/hyperactivity disorder, oppositional defiance disorder, and conduct disorder are externalizing disorders. Internalizing disorders involve thoughts and emotions and are typically characterized by anxiety or depression. Cognitive deterioration, or dementia, can occur at any point in life, but is especially prevalent in old age. There are more than a dozen causes of dementia, including Parkinson's disease, stroke, brain injury, complications of high blood pressure, and other diseases. Alzheimer's disease, which is linked to destruction of cells that produce the neurotransmitter acetylcholine, accounts for more than half of all senile dementias.