T he ability to adapt is central to being emotionally fit, healthy, and mature. An emotionally fit person is one who can adapt to changing circumstances with constructive reactions and who can enjoy living, loving others, and working productively. In everyone's life there are bound to be experiences that are anxious or deeply disturbing, such as the sadness of losing a loved one or the disappointment of failure. The emotionally fit person is stable enough not to be overwhelmed by the anxiety, grief, or guilt that such experiences frequently produce. His sense of his own worth is not lost easily by a setback in life; rather, he can learn from his own mistakes.

Types of Mental Illness

T he following discussion of classifications and types of mental illnesses is based on criteria compiled by the American Psychiatric Association in the Diagnostic and Statistical Manual of Mental Disorders .

Anxiety Disorders

Anxiety disorders are the most common emotional disorders. They are characterized by chronic feelings of uneasiness. The symptoms of an anxiety disorder are more persistent and intense than the typical feelings of nervousness or anxiety everyone feels at various times. In addition, the symptoms typically occur for no clear reason and do not go away.

There are several types of anxiety disorders. Symptoms of these disorders range from a mild, chronic sense of worry, to an overwhelming emotional condition, accompanied by such physical reactions as muscle tension, racing heart, nausea, and an increase in perspiration and blood pressure.

Panic Disorder

A person with panic disorder has recurrent attacks of intense apprehension, fear, or terror. Panic attacks may occur unexpectedly and seemingly without reason. This unpredictability tends to further intensify the feelings of tearfulness and terror.


A person with an anxiety of any place or situation from which a quick departure would be difficult or embarrassing may suffer from agoraphobia . The anxiety of agoraphobia is so severe that it can result in the outright avoidance of certain places or situations. Agoraphobia and panic disorder often occur together. People suffering from both have a fear of being in a place or situation in which they would not be able to get help if they had a panic attack.

Specific Phobias

A person with a specific phobia has an extreme or excessive fear of an object or situation that, under general conditions, is not harmful. The phobia often leads to avoidance of the object or situation altogether. People with specific phobias tend to realize that their reactions are irrational, but still are unable to overcome their fear without professional intervention. Common specific phobias include a fear of heights (acrophobia), a fear of flying (aerophobia), a fear of spiders (arachnophobia), a fear of confined spaces (claustrophobia), a fear of blood (hemophobia), and a fear of strangers (xenophobia).

Social Phobia

Also called social anxiety disorder , asocial phobia is the fear of behaving in a way that could lead to public embarrassment or ridicule in specific social situations. A person with this phobia often avoids the problematic social situation altogether. Common social phobias include a fear of public speaking, a fear of using public restrooms, and a fear of meeting new people.

Obsessive-Compulsive Disorder

A person with obsessive-compulsive disorder experiences recurrent obsessions and recurrent compulsions. Obsessions are frequently occurring thoughts that usually reflect exaggerated anxiety or fears that have no foundation in reality. Although people with obsessions realize that their thoughts are irrational, this realization is not enough to alleviate their anxiety. Instead, they engage in repetitive rituals, or compulsions, to get rid of the obsessive thoughts and thereby reduce their anxiety. Compulsive behaviors can sometimes take up more than an hour a day, and can interfere with normal daily activities and social relationships.

Common obsessions, and the compulsions which result from them, include: a preoccupation with dirt or germs, resulting in repeated hand washing and the performing of excessive housekeeping chores; second-guessing previous actions, resulting in constant checking and rechecking to satisfy doubts; a need to have items in a very specific arrangement, resulting in strict regimens to ensure order and consistency.

Post-Traumatic Stress Disorder

Post-traumatic stress disorder is characterized by the repeated experiencing or “reliving” of a traumatic event, accompanied by extreme emotional, mental, and physical distress when exposed to situations reminiscent of the trauma. People with post-traumatic stress disorder repeatedly experience their ordeal through recurrent nightmares, memories of the event, and vivid flashbacks, which may make the person feel as if they were reliving the original event. Typical events which can result in post-traumatic stress disorder include: military combat, natural disasters, violent crime, and childhood abuse.

Acute Stress Disorder

Similar to post-traumatic stress disorder, acute stress disorder differs from it in duration. Whereas post-traumatic stress disorder lasts more than a month, acute stress disorder lasts a month or less; it occurs within a month after exposure to a traumatic event.

Generalized Anxiety Disorder

Generalized anxiety disorder is characterized by chronic and overwhelming anxiety that lasts for at least six months. People with this disorder experience such persistent worry and tension that it interferes with their daily lives. Symptoms of generalized anxiety disorder include: excessive concerns (about health, family, career, or finances) even when there is no apparent reason for such concern, inability to relax, tremors, insomnia, irritability, difficulty concentrating, fatigue, and headaches.

Substance-Induced Anxiety Disorder

In a substance-induced anxiety disorder , symptoms of anxiety are present because of drug abuse, the use of medication, or exposure to a toxin.

Mood Disorders

The predominant feature of these disorders is a serious disturbance in mood. Mood disorders can be caused by biological factors, drug abuse, use of medication, toxic substances, or various medical conditions. Some people have a genetic predisposition to developing mood disorders. The development and intensity of a mood disorder can also be affected by the personality of the individual. There are two types of mood disorders: depressive and bipolar .

Depressive Disorders

In a major depressive disorder , a person has strong feelings of depression for at least two weeks. The depression may have melancholic features—that is, there may be a loss of interest or pleasure in virtually all activities.

In a dysthymic disorder , a depressed mood exists for at least 2 years. This disorder is characterized by a moderate, lingering depression, in contrast to the more intense depression characteristic of a major depressive disorder.

Other symptoms of depressive disorders include periods of prolonged sadness, changes in appetite and sleep patterns, anger, anxiety, loss of energy, feelings of worthlessness, and recurring thoughts of death or suicide.

Bipolar Disorders

There are several variations of bipolar disorders , formerly known as manic-depression . These disorders are characterized by episodes of deep depression alternating with periods of extreme elation, or manic behavior. Examples of manic behavior include the need for less sleep without feeling tired, an increase in mental and physical activity, and exaggerated enthusiasm and feelings of self-worth. A person with a bipolar disorder might take unnecessary chances and engage in risky behavior.

Schizophrenia and Other Psychotic Disorders

The defining features of these disorders are psychotic symptoms, which include a loss of contact with reality, a disorganized thought process, hallucinations, and delusions.

A disorganized thought process is reflected by a person's actions and speech. The person may behave in a bizarre manner and not be able to give a coherent explanation for his or her actions. The person's speech will not make much sense to the average person.

Hallucinations are sensations that do not result from a “real” or external stimulus, although the person experiencing the hallucination might believe otherwise. They can occur with any of the five senses, but the most common are auditory hallucinations, particularly those of hearing voices.

Delusions are erroneous beliefs that usually involve a misinterpretation of experiences. One example of a delusion is the belief of being under surveillance by the police, although in actuality no surveillance is being made. A more extreme example of a delusion is the belief of certain people that their thoughts are under the control of or are being taken away by unknown entities. Persecutory delusions —delusions of being harassed, spied on, or tormented—are the most common type.


Schizophrenia is one of the most debilitating and puzzling mental illnesses. Symptoms may include not only psychotic symptoms—disorganized thought process, hallucinations, and delusions—but also withdrawal, social isolation, lack of emotional expression, and a decrease in normal thinking and speaking activity. Schizophrenia varies in severity from person to person, and, in a given individual, from one time to another.

Most mental health professionals agree that schizophrenia is a biological illness, and that it probably occurs in individuals with a genetic susceptibility to the illness who have been exposed to other factors. These factors include such prenatal problems as exposure to influenza or lack of nutrition while the individual was growing in the mother's womb. For someone with schizophrenia, stressful social and family interactions may affect the progression of the disease, but are they not the origin.

Contrary to popular belief, a schizo phrenic does not have a “split personality.” This notion probably developed from the fact that episodes of the illness may be separated by periods of normal behavior.

There are several types of schizophrenia, with behavior ranging from excitement and aggressiveness to withdrawal and immobility.

People with paranoid schizophrenia have strong feelings of persecution. They typically feel that someone (or a group of people) is plotting to harm or kill them.

People with disorganized schizophrenia , historically known as hebephrenic schizophrenia , experience such strong speech and behavior disorganization that their ability to perform daily activities is disrupted.

In catatonic schizophrenia , a person is usually in a state of extreme withdrawal and immobility. This may alternate with occasional periods of extreme agitation or excitement.

People with residual schizophrenia exhibit the absence of normal behaviors. For example, they may withdraw, lack emotional expression, isolate themselves from society, and experience a decrease in thinking and speaking activity.

In undifferentiated schizophrenia , a person exhibits a variety of schizophrenic symptoms, but none of them is dominant.

Psychotic Disorders

Other disorders included in the category of Schizophrenia and Psychotic Disorders follow, along with some defining features of each disorder.

Both brief psychotic disorder and schizophreniform disorder have the same symptoms as schizophrenia, but the symptoms do not last long enough to warrant a diagnosis of schizophrenia. In brief psychotic disorder, the symptoms last more than a day, but less than one month. In schizophreniform disorder, the symptoms last from one to six months.

In schizoaffective disorder , a person displays symptoms of a mood disorder—either bipolar or depressive—in addition to psychotic symptoms.

In a delusional disorder , a person experiences one or more delusions based on situations that could conceivably be happening to the person, but for which there is no evidence. The delusions must persist for at least one month in order to be classified as a delusional disorder.

In a shared psychotic disorder , a person is influenced by someone else who already has a similar delusion.

In a substance-induced psychotic disorder , the psychotic symptoms present are the result of drug abuse, medication, or exposure to a toxin.

Personality Disorders

These disorders are characterized by a persistent pattern of noticeably unusual behavior and ways of thinking.

A paranoid personality disorder is characterized by a pattern of suspicion and distrust A person with this disorder will misconstrue other people's intentions as being malicious.

A schizoid personality disorder is characterized by a pattern of disinterest in social relationships. A person with this disorder may be fearful of close interaction with others. They also have a limited range of emotional expression.

People with schizotypal personality disorder are socially and emotionally distant. Their thinking process is odd and distorted, and these oddities are evident through their speech and behavior.

An antisocial personality disorder is characterized by a pattern of disregarding and violating the rights of others. People with this disorder typically do not feel remorse or guilt after inflicting harm upon others. This disorder usually develops in adolescence and often continues into adulthood, although the severity of the disorder can diminish as a person ages.

A borderline personality disorder is characterized by a pattern of instability in relationships. A person with this disorder also displays symptoms of impulsiveness and irritability.

In histrionic personalty disorder , there is a pattern of attention-seeking behavior and excessive displays of emotion. A person with this disorder may easily fall under the influence of others in an effort to be the center of attention.

A narcissistic personality disorder is characterized by an exaggerated sense of self-importance. A person with this disorder requires excessive admiration and lacks empathy for others.

An avoidant personality disorder is characterized by feelings of inadequacy. A person with this disorder will avoid activities that require significant interpersonal interaction, and tends to be hypersensitive to negative evaluation.

A dependent personality disorder is characterized by an excessive need to be taken care of. A person with this disorder has a pattern of submissive and clinging behavior.

An obsessive-compulsive personality disorder is characterized by a preoccupation with orderliness, perfectionism, and control. A person with this disorder will appear inflexible and stubborn to others.

Dissociative Disorders

In these disorders, there is a disruption in consciousness, memory, identity, or perception. The disruption may occur suddenly, or it may gradually develop. It can also take the form of a brief affliction or a chronic condition.

A person with dissociative amnesia is unable to recall relevant personal information. The “forgotten” information is usually disturbing to the individual, and of a traumatic nature. For example, a person who attempts to commit suicide might not later remember anything at all regarding the incident.

A dissociative fugue is characterized by a sudden loss of personal identity and of the memory of one's past life. This is accompanied by the tendency to suddenly wander far from one's home or place of work. In some cases, the individual also assumes a new identity. The disorder can last from a couple of hours to several months. A dissociative fugue is usually brought on by traumatic events or an overwhelming accumulation of tension and stress. It is a rare disorder.

Dissociative identity disorder , formerly called multiple personality disorder , refers to the presence of two or more distinct personalities, each of which dominate an individual's behavior at different times. This disorder is also characterized by gaps in the individual's memory that vary, depending on which personality is currently dominant. For example, a weaker personality may not remember what happens during the times that a stronger personality is dominating the individual's behavior.

Depersonalization disorder is characterized by persistent feelings of detachment from one's own body or thoughts. The feelings of depersonalization can be severe and occur often enough that one's life is disrupted, and treatment is needed. In many cases, though, the sense of depersonalization is brief and minimal, and treatment is not needed.

Factitious Disorder

This disorder is characterized by physical or psychological symptoms that are deliberately produced or feigned in order to appear sick. People with this disorder might inflict harm upon themselves, exaggerate an existing medical complaint, or completely fabricate a new and false medical problem, for the sole purpose of appearing ill.

Somatoform Disorders

In these disorders, a person has physical symptoms of a physical disease, but does not have the disease. The physical symptoms are caused by psychological factors and are not intentionally produced by the individual. Examples of physical symptoms common in somatoform disorders include blindness, paralysis, respiratory distress, and heart problems.

A person with a somatization disorder has recurrent and multiple physical complaints and symptoms for which there is no known medical cause. There is evidence, or a strong presumption, that the symptoms are related to psychological reasons. Symptoms vary from person to person and also depend upon their underlying emotional conflict.

A person with a conversion disorder experiences emotional distress that is “converted” into physical symptoms. The physical symptoms have no biological cause, and are not a part of a somatization disorder. A person who witnesses a terrifying event and then develops blindness would be an extreme example of this disorder.

Hypochondriasis is the preoccupation with the fear of acquiring or the belief of having a serious disease. A person reaches this conclusion by overreacting to normal bodily functions and minor abnormalities. People with hypochondriasis will persist in their fears and beliefs despite medical tests and exams that prove that they do not have a serious disease.

A person with body dysmorphic disorder is preoccupied with an imagined or insignificant defect in one's own appearance.

Sexual and Gender Identity Disorders

These disorders involve sexual performance, sexual deviance, and concepts of appropriate gender roles. They include the categories of sexual dysfunctions, paraphilias, and gender identity disorders.

Sexual dysfunctions refer to changes in personal sexual desires and activities that the individual finds unfulfilling, or inadequate. Examples of sexual dysfuntions include pain during sexual activity and complications with sexual arousal and desire.

Persistent and intense sexual urges or behaviors that involve unusual objects or situations are called paraphilias . Examples of paraphilias include exhibitionism (exposing one's self), voyeurism (observing sexual activity), sadism (inflicting pain or humiliation), and masochism (receiving pain or humiliation).

A gender identity disorder is characterized by intense, persistent feelings of discomfort or inappropriateness with one's own gender, in addition to a strong identification with the opposite gender. People with gender identity disorders may engage in cross-dressing, hormone treatment, or surgery to acquire the physical appearance of the opposite sex.

Other Disorders

Several other types of disorders are discussed elsewhere in this encyclopedia. These disorders include:

Eating Disorders. See Chapter 3, The Teens , subtitles Anorexia Nervosa, and Bulimia.

Disorders Usually First Diagnosed in Infancy, Childhood, or Adolescence. See Chapter 2, The First Dozen Years , subtitles Autism, Brain Damage, Developmental Disability, Dyslexia, Hyperactivity, Learning Disability, Mental Illness, Mental Retardation, Pica, Speech Impediments, and Stuttering. Chapter 28, Mental and Emotional Disorders , subtitle Mental Retardation.

Sleep Disorders. See Chapter 2, The First Dozen Years , subtitles Dreams and Nightmares, Sleepwalking. Chapter 37, Encyclopedic Guide to the Body , Health and Medicine , subtitles Narcolepsy, Sleep, Sleep Apnea, Snoring. Chapter 5, The Middle Years , subtitle Rest and Sleep.

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