The disorder depression is a feeling of sadness intense enough to interfere with functioning and/or a decreased interest or pleasure in activities. It may follow a recent loss or other sad event but is out of proportion to that event and lasts beyond an appropriate length of time.
People often use the term depression to describe the sad or discouraged mood that results from emotionally distressing events, such as a natural disaster, a serious illness, or death of a loved one. People may also say they feel depressed at certain times, such as during the holidays (holiday blues) or on the anniversary of a loved one's death. However, such feelings do not usually represent a disorder. Usually, these feelings are temporary, lasting days rather than weeks or months, and occur in waves that tend to be tied to thoughts or reminders of the distressing event. Also, these feelings do not substantially interfere with functioning for any length of time.
After anxiety, depression is the most common mental health disorder. About 30% of people who visit a primary care practitioner have symptoms of depression, but fewer than 10% of these people have major depression.
Depressive disorders typically develop during a person's mid teens, 20s, or 30s, although depression can begin at almost any age, including during childhood (see Depression in Children and Adolescents).
An episode of depression, if untreated, typically lasts about 6 months but sometimes lasts for 2 years or more. Episodes tend to recur several times over a lifetime.
The exact cause of depression is unclear, but a number of factors may make depression more likely. Risk factors include
Depression does not reflect a weakness of character and may not reflect a personality disorder, childhood trauma, or poor parenting. Social class, race, and culture do not appear to affect the chance that people will experience depression during their lifetime. Depression may arise or worsen without any apparent or significant life stresses.
Genetic abnormalities may contribute. They can affect the function of substances that help nerve cells communicate (neurotransmitters). Serotonin, dopamine, and norepinephrine are neurotransmitters that may be involved in depression.
Women are more likely than men to experience depression, although the reasons are not entirely clear. Of physical factors, hormones are the ones most involved. Changes in hormone levels, which can cause mood changes shortly before menstruation (see Premenstrual Syndrome) and after childbirth, might play some role in women. During the first 4 weeks after giving birth, some women become depressed (called baby blues or, if the depression is more serious, postpartum depression—see Postpartum Depression). Abnormal thyroid function, which is fairly common among women, may also be a factor.
Depression may occur with or be caused by a number of physical disorders and factors. Physical disorders may cause depression directly (as when a thyroid disorder affects hormone levels) or indirectly (as when rheumatoid arthritis causes pain and disability). Often, a physical disorder both directly and indirectly causes depression. For example, AIDS may cause depression directly if the human immunodeficiency virus (HIV), which causes AIDS, damages the brain. AIDS may cause depression indirectly by having an overall negative effect on the person's life. Many people report feeling sadder in late autumn and winter and blame this tendency on the shortening of daylight hours and colder temperatures. However, in some people, such sadness is severe enough to be considered a type of depression.
The use of some prescription drugs, such as some beta-blockers (used to treat high blood pressure), can cause depression. For unknown reasons, corticosteroids often cause depression when the body produces them in large amounts as part of a disorder (as in Cushing syndrome), but when they are given as a drug, they tend to cause hypomania (a less severe form of mania) or, rarely, mania (see Bipolar Disorder (Manic-Depressive Illness)). Sometimes stopping a drug can cause temporary depression.
A number of mental health disorders can predispose a person to depression. They include certain anxiety disorders, alcoholism, other substance abuse disorders, and schizophrenia. People who have had depression are more likely to have it again.
Emotionally distressing events, such as loss of a loved one, can sometimes trigger depression, particularly in people who predisposed to depression, such as those who have family members with depression.
|PrintOpen table in new window
|Some Causes of Depression
Brain and nervous system disorders
Dementia (in early stages)
Seizures that affect the temporal lobe (complex partial seizures)
Cancer spreading throughout the body (metastatic)
Cancer of the pancreas
Connective tissue disorders
Systemic lupus erythematosus (lupus)
High levels of parathyroid hormone (hyperparathyroidism)
Low or high levels of thyroid hormone (hypothyroidism or hyperthyroidism)
Low levels of pituitary hormones (hypopituitarism)
Low levels of testosterone (hypogonadism)
Syphilis (late stage)
Pellagra (vitamin B6 deficiency)
Pernicious anemia (a form of vitamin B12 deficiency)
Hormone (estrogen) therapy
Symptoms typically develop gradually over days or weeks and can vary greatly. For example, a person who is becoming depressed may appear sluggish and sad or irritable and anxious.
Many people with depression cannot experience emotions—including grief, joy, and pleasure—in a normal way. The world may appear to have become colorless and lifeless. They lose interest or pleasure in activities that they used to enjoy.
Depressed people may be preoccupied with intense feelings of guilt and self-denigration and may not be able to concentrate. They may experience feelings of despair, loneliness, and worthlessness. They are often indecisive and withdrawn, feel progressively helpless and hopeless, and think about death and suicide.
Most depressed people have difficulty falling asleep and awaken repeatedly, particularly early in the morning. Poor appetite and weight loss may lead to emaciation, and in women, menstrual periods may stop. However, overeating and weight gain are common in people with mild depression.
Some depressed people neglect personal hygiene or even their children, other loved ones, or pets. Some complain of having a physical illness, with various aches and pains.
The term depression is used to describe several related disorders:
Major depressive disorder:
People are depressed most days for at least 2 weeks. People who have a major depressive disorder may appear miserable. Their eyes may be full of tears, their brows may be furrowed, and the corners of the mouth may be turned down. They may slump and avoid eye contact. They may hardly move, show little facial expression, and speak in a monotone.
Persistent depressive disorder:
People have been depressed for most of the time for 2 years or more.
Symptoms begin gradually, often during adolescence, and may last for years or decades. How many symptoms are present at one time varies, and sometimes symptoms are less severe than those in major depression.
People with this disorder may be gloomy, pessimistic, skeptical, humorless, and incapable of having fun. Some are passive, lack energy, and keep to themselves. Some constantly complain and are quick to criticize others and reproach themselves. They may be preoccupied with inadequacy, failure, and negative events, sometimes to the point of morbid enjoyment of their own failures.
Premenstrual dysphoric disorder:
Severe symptoms occur before most menstrual periods and disappear after they end. Symptoms cause substantial distress and/or greatly interfere with functioning. Symptoms are similar to those of premenstrual syndrome (see Premenstrual Syndrome) but are more severe, causing great distress and interfering with functioning at work and social interactions.
This disorder may first appear any time after girls start to menstruate. It may worsen as women approach menopause but ends after menopause. It occurs in about 2 to 6% of women who are menstruating.
Women have mood swings, suddenly becoming sad and tearful. They are irritable and anger easily. They feel very depressed, hopeless, anxious, and on edge. They may feel overwhelmed or out of control. They often put themselves down.
As with other types of depression, women with this disorder may lose interest in their usual activities, have difficulty concentrating, and feel tired and without energy. They may eat too much and crave certain foods. They may sleep too little or too much.
Like many women whose period is about to start, these women may have tender, swollen breasts and/or achy muscles and joints. They may feel bloated and gain weight.
Doctors use certain terms to describe specific symptoms that can occur in people with depression. These terms include
Thoughts of death are among the most serious symptoms of depression. Many depressed people want to die or feel they are so worthless that they should die. As many as 15% of untreated depressed people end their life by suicide. A suicide threat is an emergency (see Suicidal Behavior). When people threaten to kill themselves, a doctor may hospitalize them so that they can be supervised until treatment reduces the risk of suicide. The risk is especially high in the following situations:
People with depression are more likely to abuse alcohol or other recreational drugs in an attempt to help them sleep or feel less anxious. However, depression causes alcoholism and drug abuse less often than was once thought. People are also more likely to smoke heavily and to neglect their health. Thus, the risk of developing or worsening other disorders, such as chronic obstructive pulmonary disease, is increased.
A doctor is usually able to diagnose depression based on symptoms. A previous history of depression or a family history of depression helps confirm the diagnosis. Excessive worrying, panic attacks, and obsessions are common in depression and may lead the doctor to incorrectly think that the person has an anxiety disorder.
In older people, depression may be difficult to notice, especially if they do not work or have little social interaction. Also, depression may be mistaken for dementia because it can cause similar symptoms, such as confusion and difficulty concentrating and thinking clearly. However, when such symptoms are caused by depression, they resolve when depression is treated. When dementia is the cause, they do not resolve.
Standardized questionnaires are used to help identify depression and determine how severe it is, but they cannot be used alone to diagnose depression. Two such questionnaires are the Hamilton Depression Rating Scale, conducted verbally by an interviewer, and the Beck Depression Inventory, a self-administered questionnaire. Doctors also ask people whether they have any thoughts or plans to harm themselves. Such thoughts indicate that depression is severe.
No test can confirm depression. However, laboratory tests may help a doctor determine whether depression is caused by an endocrine or other physical disorder For example, blood tests are usually done to detect a thyroid disorder or vitamin deficiency. In younger people, tests may be done to detect drug abuse. A thorough neurologic examination is done to check for Parkinson disease, which causes some of the same symptoms. People who have severely disturbed sleep may need to have testing (polysomnography—see Testing) to distinguish sleep disorders from depression.
Most people with depression do not require hospitalization. However, some people should be hospitalized, especially if they are contemplating suicide or have attempted it, are frail because of weight loss, or are at risk of heart problems because of severe agitation.
Treatment depends the severity and type of depression:
Depression can usually be treated successfully. If a cause (such as a drug or another disorder) can be identified, it is corrected first, but drugs to treat depression may also be needed.
Doctors may schedule visits or telephone calls every week or every other week for people with depression. Doctors explain to them and their family members that depression has physical causes and requires specific treatment, which is usually effective. Doctors reassure them that depression does not reflect a character flaw, such as weakness.
Learning about depression can help people understand and deal with the disorder. For example, people learn that the path to recovery is often bumpy and that episodes of sadness and dark thoughts may recur but they will stop. Thus, people can put any setbacks in perspective and are more likely to continue their treatment and not give up.
Becoming more active—taking walks and exercising regularly—can help, as can interacting more with others.
Support groups (such as the Depression and Bipolar Support Alliance—DBSA) can help by providing a forum to share commons experiences and feelings.
Psychotherapy alone may be just as effective as drug therapy for mild depression. When used with drugs, it can be useful for severe depression.
Individual or group psychotherapy can help people with depression gradually resume former responsibilities and adapt to the normal pressures of life. Interpersonal therapy focuses on the person's past and present social roles, identifies problems with how the person interacts with other people, and provides guidance as the person adjusts to changes in life roles. Cognitive-behavioral therapy can help change hopelessness and negative thinking.
Several types of antidepressants—selective serotonin reuptake inhibitors (SSRIs), heterocyclic antidepressants, monoamine oxidase inhibitors (MAOIs), and several newer types—are available, as well as psychostimulants. Most must be taken regularly for at least several weeks before they begin to work. Most people need to take antidepressants for 6 to 12 months to prevent relapses. People over 50 may have to take them for up to 2 years.
Side effects vary with each type of drug. Sometimes when treatment with one drug does not relieve depression, a different type (class) or a combination of antidepressant drugs is prescribed.
Selective serotonin reuptake inhibitors (SSRIs) are now the most commonly used class of antidepressants. SSRIs are effective in treating depression as well as other mental health disorders that often coexist with depression. Although SSRIs can cause nausea, diarrhea, tremor, weight loss, and headache, these side effects are usually mild or go away with continued use. Most people tolerate the side effects of SSRIs better than the side effects of heterocyclic antidepressants. SSRIs are less likely to adversely affect the heart than heterocyclic antidepressants. However, a few people may seem more agitated, depressed, and anxious the first week after they start SSRIs or the dose is increased. These people, especially younger children and adolescents, may become increasingly suicidal if these symptoms are not detected and rapidly treated. People taking SSRIs and their loved ones should be warned of this possibility and instructed to call their doctor if symptoms worsen with treatment. However, because people with untreated depression also sometimes commit suicide, people and their doctors must balance this risk against the risk of drug treatment. Also, with long-term use, SSRIs may have additional side effects, such as weight gain and sexual dysfunction (in one third of people). Abruptly stopping some of the SSRIs may result in a discontinuation syndrome that includes dizziness, anxiety, irritability, nausea, and flu-like symptoms.
Newer antidepressants are as effective and safe as SSRIs and have similar side effects. These drugs include
As may occur with SSRIs, the risk of suicide may be temporarily increased when these drugs are first started, and abruptly stopping serotonin-norepinephrine reuptake inhibitors may result in a discontinuation syndrome.
Heterocyclic (including tricyclic) antidepressants, once the mainstay of treatment, are now used infrequently because they have more side effects than other antidepressants. They often cause drowsiness and lead to weight gain. They can also cause an increase in heart rate and a decrease in blood pressure when a person stands (called orthostatic hypotension—see Dizziness or Light-Headedness When Standing Up). Other side effects, called anticholinergic effects, include blurred vision, dry mouth, confusion, constipation, and difficulty starting to urinate. Anticholinergic effects are often more severe in older people (see Sidebar 1: Anticholinergic: What Does It Mean? ). Abruptly stopping heterocyclic antidepressants, as with SSRIs, may result in a discontinuation syndrome.
Monoamine oxidase inhibitors (MAOIs) are very effective but are rarely prescribed except when other antidepressants have not worked. People who use MAOIs must adhere to a number of dietary restrictions and take special precautions to avoid a serious reaction involving a sudden, severe rise in blood pressure with a severe, throbbing headache (hypertensive crisis). This crisis can cause a stroke. Precautions include
People who take MAOIs should also avoid taking other types of antidepressants, including heterocyclic antidepressants, SSRIs, bupropion, serotonin modulators, and serotonin-norepinephrine reuptake inhibitors. Taking an MAOI with another antidepressant can cause a dangerously high body temperature, breakdown of muscle, kidney failure, and seizures. These effects, called neuroleptic malignant syndrome, can be fatal.
Psychostimulants, such as dextroamphetamine and methylphenidate, as well as other drugs, are sometimes used, often with antidepressants.
St. John's wort, an herbal dietary supplement, is sometimes used to relieve mild depression, although its effectiveness is not proven. Due to potentially harmful interactions between St. John's wort and many prescription drugs, people interested in taking this herbal supplement need to discuss possible drug interactions with their doctor (see St. John's Wort).
|PrintOpen table in new window
Electroconvulsive therapy is sometimes used to treat people with severe depression, including people who are psychotic, threatening to commit suicide, or refusing to eat. It is also used to treat depression during pregnancy when drugs are ineffective. This type of therapy is usually very effective and can relieve depression quickly, unlike most antidepressants, which can take up to several weeks. The speed with which it takes effect can save lives. After electroconvulsive therapy is stopped, episodes of depression can recur. To help prevent them, doctors often prescribe antidepressants.
For electroconvulsive therapy, electrodes are placed on the head, and an electrical current is applied to induce a seizure in the brain. For reasons that are not understood, the seizure relieves depression. Usually, at least five to seven treatments, one treatment every other day, are given. Because the electrical current can cause muscle contractions and pain, general anesthesia is required during treatments. Electroconvulsive therapy may cause some temporary memory loss and, rarely, permanent memory loss.
Phototherapy is the most effective treatment for seasonal depression but may be helpful for other types of depressive disorders. Phototherapy involves sitting a specific distance from a light box that provides light with the necessary intensity. People are instructed not to look directly at the light and to remain in front of the light for at least 30 minutes. The time of day that phototherapy is used depends on when people usually go to sleep and wake up.
Last full review/revision September 2014 by William Coryell, MD