Depression (psychology), mental illness in which a person experiences deep, unshakable sadness and diminished interest in nearly all activities. People also use the term depression to describe the temporary sadness, loneliness, or blues that everyone feels from time to time. In contrast to normal sadness, severe depression, also called major depression, can dramatically impair a person’s ability to function in social situations and at work. People with major depression often have feelings of despair, hopelessness, and worthlessness, as well as thoughts of committing suicide.
Depression can take several other forms. In bipolar disorder, sometimes called manic-depressive illness, a person’s mood swings back and forth between depression and mania. People with seasonal affective disorder typically suffer from depression only during autumn and winter, when there are fewer hours of daylight. In dysthymia (pronounced dis-THI-mee-uh), people feel depressed, have low self-esteem, and concentrate poorly most of the time—often for a period of years—but their symptoms are milder than in major depression. Some people with dysthymia experience occasional episodes of major depression. Mental health professionals use the term clinical depression to refer to any of the above forms of depression.
Surveys indicate that people commonly view depression as a sign of personal weakness, but psychiatrists and psychologists view it as a real illness. In the United States, the National Institute of Mental Health has estimated that depression costs society many billions of dollars each year, mostly in lost work time.
Depression is one of the most common mental illnesses. At least 8 percent of adults in the United States experience serious depression at some point during their lives, and estimates range as high as 17 percent. The illness affects all people, regardless of sex, race, ethnicity, or socioeconomic standing. However, women are two to three times more likely than men to suffer from depression. Experts disagree on the reason for this difference. Some cite differences in hormones, and others point to the stress caused by society’s expectations of women.
Depression occurs in all parts of the world, although the pattern of symptoms can vary. The prevalence of depression in other countries varies widely, from 1.5 percent of people in Taiwan to 19 percent of people in Lebanon. Some researchers believe methods of gathering data on depression account for different rates.
A number of large-scale studies indicate that depression rates have increased worldwide over the past several decades. Furthermore, younger generations are experiencing depression at an earlier age than did previous generations. Social scientists have proposed many explanations, including changes in family structure, urbanization, and reduced cultural and religious influences.
Although it may appear anytime from childhood to old age, depression usually begins during a person’s 20s or 30s. The illness may come on slowly, then deepen gradually over months or years. On the other hand, it may erupt suddenly in a few weeks or days. A person who develops severe depression may appear so confused, frightened, and unbalanced that observers speak of a “nervous breakdown.” However it begins, depression causes serious changes in a person’s feelings and outlook. A person with major depression feels sad nearly every day and may cry often. People, work, and activities that used to bring them pleasure no longer do.
Symptoms of depression can vary by age. In younger children, depression may include physical complaints, such as stomachaches and headaches, as well as irritability, “moping around,” social withdrawal, and changes in eating habits. They may feel unenthusiastic about school and other activities. In adolescents, common symptoms include sad mood, sleep disturbances, and lack of energy. Elderly people with depression usually complain of physical rather than emotional problems, which sometimes leads doctors to misdiagnose the illness.
Symptoms of depression can also vary by culture. In some cultures, depressed people may not experience sadness or guilt but may complain of physical problems. In Mediterranean cultures, for example, depressed people may complain of headaches or nerves. In Asian cultures they may complain of weakness, fatigue, or imbalance.
If left untreated, an episode of major depression typically lasts eight or nine months. About 85 percent of people who experience one bout of depression will experience future episodes.
A Appetite and Sleep Changes
Depression usually alters a person’s appetite, sometimes increasing it, but usually reducing it. Sleep habits often change as well. People with depression may oversleep or, more commonly, sleep for fewer hours. A depressed person might go to sleep at midnight, sleep restlessly, then wake up at 5 am feeling tired and blue. For many depressed people, early morning is the saddest time of the day.
B Changes in Energy Level
Depression also changes one’s energy level. Some depressed people may be restless and agitated, engaging in fidgety movements and pacing. Others may feel sluggish and inactive, experiencing great fatigue, lack of energy, and a feeling of being worn out or carrying a heavy burden. Depressed people may also have difficulty thinking, poor concentration, and problems with memory.
C Poor Self-Esteem
People with depression often experience feelings of worthlessness, helplessness, guilt, and self-blame. They may interpret a minor failing on their part as a sign of incompetence or interpret minor criticism as condemnation. Some depressed people complain of being spiritually or morally dead. The mirror seems to reflect someone ugly and repulsive. Even a competent and decent person may feel deficient, cruel, stupid, phony, or guilty of having deceived others. People with major depression may experience such extreme emotional pain that they consider or attempt suicide. At least 15 percent of seriously depressed people commit suicide, and many more attempt it.
D Psychotic Symptoms
In some cases, people with depression may experience psychotic symptoms, such as delusions (false beliefs) and hallucinations (false sensory perceptions). Psychotic symptoms indicate an especially severe illness. Compared to other depressed people, those with psychotic symptoms have longer hospital stays, and after leaving, they are more likely to be moody and unhappy. They are also more likely to commit suicide. See Psychosis.
Some depressions seem to come out of the blue, even when things are going well. Others seem to have an obvious cause: a marital conflict, financial difficulty, or some personal failure. Yet many people with these problems do not become deeply depressed. Most psychologists believe depression results from an interaction between stressful life events and a person’s biological and psychological vulnerabilities.
A Biological Factors
Depression runs in families. By studying twins, researchers have found evidence of a strong genetic influence in depression. Genetically identical twins raised in the same environment are three times more likely to have depression in common than fraternal twins, who have only about half of their genes in common. In addition, identical twins are five times more likely to have bipolar disorder in common. These findings suggest that vulnerability to depression and bipolar disorder can be inherited. Adoption studies have provided more evidence of a genetic role in depression. These studies show that children of depressed people are vulnerable to depression even when raised by adoptive parents.
Genes may influence depression by causing abnormal activity in the brain. Studies have shown that certain brain chemicals called neurotransmitters play an important role in regulating moods and emotions. Neurotransmitters involved in depression include norepinephrine, dopamine, and serotonin. Research in the 1960s suggested that depression results from lower than normal levels of these neurotransmitters in parts of the brain. Support for this theory came from the effects of antidepressant drugs, which work by increasing the levels of neurotransmitters involved in depression. However, later studies have discredited this simple explanation and have suggested a more complex relationship between neurotransmitter levels and depression.
An imbalance of hormones may also play a role in depression. Many depressed people have higher than normal levels of hydrocortisone (cortisol), a hormone secreted by the adrenal gland in response to stress. In addition, an underactive or overactive thyroid gland can lead to depression.
A variety of medical conditions can cause depression. These include dietary deficiences in vitamin B6, vitamin B12, and folic acid (see Vitamin); degenerative neurological disorders, such as Alzheimer’s disease and Huntington’s disease (see Chorea); strokes in the frontal part of the brain; and certain viral infections, such as hepatitis and mononucleosis. Certain medications, such as steroids, may also cause depression.
B Psychological Factors
Psychological theories of depression focus on the way people think and behave. In a 1917 essay, Austrian psychoanalyst Sigmund Freud explained melancholia, or major depression, as a response to loss—either real loss, such as the death of a spouse, or symbolic loss, such as the failure to achieve an important goal. Freud believed that a person’s unconscious anger over loss weakens the ego, resulting in self-hate and self-destructive behavior.
Cognitive theories of depression emphasize the role of irrational thought processes. American psychiatrist Aaron Beck proposed that depressed people tend to view themselves, their environment, and the future in a negative light because of errors in thinking. These errors include focusing on the negative aspects of any situation, misinterpreting facts in negative ways, and blaming themselves for any misfortune. In Beck’s view, people learn these self-defeating ways of looking at the world during early childhood. This negative thinking makes situations seem much worse than they really are and increases the risk of depression, especially in stressful situations.
In support of this cognitive view, people with “depressive” personality traits appear to be more vulnerable than others to actual depression. Examples of depressive personality traits include gloominess, pessimism, introversion, self-criticism, excessive skepticism and criticism of others, deep feelings of inadequacy, and excessive brooding and worrying. In addition, people who regularly behave in dependent, hostile, and impulsive ways appear at greater risk for depression.
American psychologist Martin Seligman proposed that depression stems from “learned helplessness,” an acquired belief that one cannot control the outcome of events. In this view, prolonged exposure to uncontrollable and inescapable events leads to apathy, pessimism, and loss of motivation. An adaptation of this theory by American psychologist Lynn Abramson and her colleagues argues that depression results not only from helplessness, but also from hopelessness. The hopelessness theory attributes depression to a pattern of negative thinking in which people blame themselves for negative life events, view the causes of those events as permanent, and overgeneralize specific weaknesses as applying to many areas of their life.
C Stressful Events
Psychologists agree that stressful experiences can trigger depression in people who are predisposed to the illness. For example, the death of a loved one may trigger depression. Psychologists usually distinguish true depression from grief, a normal process of mourning a loved one who has died. Other stressful experiences may include divorce, pregnancy, the loss of a job, and even childbirth. About 20 percent of women experience an episode of depression, known as postpartum depression, after having a baby. In addition, people with serious physical illnesses or disabilities often develop depression.
People who experience child abuse appear more vulnerable to depression than others. So, too, do people living under chronically stressful conditions, such as single mothers with many children and little or no support from friends or relatives.
Depression typically cannot be shaken or willed away. An episode must therefore run its course until it weakens either on its own or with treatment. Depression can be treated effectively with antidepressant drugs, psychotherapy, or a combination of both.
Despite the availability of effective treatment, most depressive disorders go untreated and undiagnosed. Studies indicate that general physicians fail to recognize depression in their patients at least half of the time. In addition, many doctors and patients view depression in elderly people as a normal part of aging, even though treatment for depression in older people is usually very effective.
A Antidepressant Drugs
Up to 70 percent of people with depression respond to antidepressant drugs. These medications appear to work by altering the levels of serotonin, norepinephrine, and other neurotransmitters in the brain. They generally take at least two to three weeks to become effective. Doctors cannot predict which type of antidepressant drug will work best for any particular person, so depressed people may need to try several types. Antidepressant drugs are not addictive, but they may produce unwanted side effects. To avoid relapse, people usually must continue taking the medication for several months after their symptoms improve.
Commonly used antidepressant drugs fall into three major classes: tricyclics, monoamine oxidase inhibitors (MAO inhibitors), and selective serotonin reuptake inhibitors (SSRIs). Tricyclics, named for their three-ring chemical structure, include amitriptyline (Elavil), imipramine (Tofanil), desipramine (Norpramin), doxepin (Sinequan), and nortriptyline (Pamelor). Side effects of tricyclics may include drowsiness, dizziness upon standing, blurred vision, nausea, insomnia, constipation, and dry mouth.
MAO inhibitors include isocarboxazid (Marplan), phenelzine (Nardil), and tranylcypromine (Parnate). People who take MAO inhibitors must follow a diet that excludes tyramine—a substance found in wine, beer, some cheeses, and many fermented foods—to avoid a dangerous rise in blood pressure. In addition, MAO inhibitors have many of the same side effects as tricyclics.
Selective serotonin reuptake inhibitors include fluoxetine (Prozac), sertraline (Zoloft), and paroxetine (Paxil). These drugs generally produce fewer and milder side effects than do other types of antidepressants, although SSRIs may cause anxiety, insomnia, drowsiness, headaches, and sexual dysfunction. Some patients have alleged that Prozac causes violent or suicidal behavior in a small number of cases, but the U.S. Food and Drug Administration has failed to substantiate this claim.
Prozac became the most widely used antidepressant in the world soon after its introduction in the late 1980s by drug manufacturer Eli Lilly and Company. Many people find Prozac extremely effective in lifting depression. In addition, some people have reported that Prozac actually tranforms their personality by increasing their self-confidence, optimism, and energy level. However, mental health professionals have expressed serious ethical concerns over Prozac’s use as a “personality enhancer,” especially among people without clinical depression.
Doctors often prescribe lithium carbonate, a natural mineral salt, to treat people with bipolar disorder (see Lithium). People often take lithium during periods of relatively normal mood to delay or even prevent subsequent mood swings. Side effects of lithium include nausea, stomach upset, vertigo, and frequent urination.
Studies have shown that short-term psychotherapy can relieve mild to moderate depression as effectively as antidepressant drugs. Unlike medication, psychotherapy produces no physiological side effects. In addition, depressed people treated with psychotherapy appear less likely to experience a relapse than those treated only with antidepressant medication. However, psychotherapy usually takes longer to produce benefits.
There are many kinds of psychotherapy. Cognitive-behavioral therapy assumes that depression stems from negative, often irrational thinking about oneself and one’s future. In this type of therapy, a person learns to understand and eventually eliminate those habits of negative thinking. In interpersonal therapy, the therapist helps a person resolve problems in relationships with others that may have caused the depression. The subsequent improvement in social relationships and support helps alleviate the depression. Psychodynamic therapy views depression as the result of internal, unconscious conflicts. Psychodynamic therapists focus on a person’s past experiences and the resolution of childhood conflicts. Psychoanalysis is an example of this type of therapy. Critics of long-term psychodynamic therapy argue that its effectiveness is scientifically unproven.
C Other Treatments
Electroconvulsive therapy (ECT) can often relieve severe depression in people who fail to respond to antidepressant medication and psychotherapy. In this type of therapy, a low-voltage electric current is passed through the brain for one to two seconds to produce a controlled seizure. Patients usually receive six to ten ECT treatments over several weeks. ECT remains controversial because it can cause disorientation and memory loss. Nevertheless, research has found it highly effective in alleviating severe depression.
For milder cases of depression, regular aerobic exercise may improve mood as effectively as psychotherapy or medication. In addition, some research indicates that dietary modifications can influence one’s mood by changing the level of serotonin in the brain.
David B. Cohen