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Medically reviewed by Last updated on Mar 8, 2023.

What is Depression?

Harvard Health Publishing

Depression is more than just a passing blue mood, a "bad day," or temporary sadness. The most common symptom is a low mood that can sometimes appear as irritability. Often the person with depression is not able to enjoy activities that he or she normally enjoys.

In major depression, people experience profound sadness, a sense of despair, or a loss of enjoyment. The symptoms of major depression are defined as lasting at least two weeks, but usually they go on much longer.

Another type of depressive disorder, persistent depressive disorder (previously known as dysthymia), has fewer symptoms than an episode of major depression, but lasts much longer (at least two years in adults and at least one year in children and adolescents). Many people with this disorder describe having been depressed as long as they can remember, or feeling as though they go in and out of depression all the time.

A variety of symptoms usually accompany the low mood of any type of depression. And the symptoms can vary significantly among different people.

Many people with depression also have anxiety. They may worry more than average about their physical health. They may have excessive conflict in their relationships or function poorly at work. Sexual functioning may be a problem. People with depression are also at more risk for abusing alcohol or other substances.

Depression probably involves changes in the areas of the brain that control mood. The nerve cells may be functioning poorly in certain regions of the brain. Altered communication between nerve cells or nerve circuits can make it harder for a person's brain to regulate his or her mood.

Hormone changes may also negatively affect mood. An individual's life experiences can affect these biological processes. And a person's genetic makeup influences how vulnerable he or she is to experiencing depression.

An episode of depression can be triggered by a stressful life event. But in many cases, depression does not appear to be related to a specific event.

A major depressive episode may occur within the first year after giving birth to a baby. In that case, it may be called major depressive disorder with peripartum onset. Most people refer to it as postpartum depression.

Depression that occurs mainly during the winter months is usually called seasonal affective disorder, or SAD. It also may be called major depressive disorder with seasonal pattern.

Episodes of depression can occur at any age. Depression is diagnosed in women twice as often as in men. People who have a family member with major depression are more likely to develop depression or drinking problems.


A depressed person may gain or lose weight, eat more or less than usual, have difficulty concentrating, and have trouble sleeping or sleep more than usual. He or she may feel tired and have no energy for work or play. Small burdens or obstacles may appear impossible to manage. The person can appear slowed down, or agitated and restless. The symptoms can be quite noticeable to others.

A particularly painful symptom of this illness is an unshakable feeling of worthlessness and guilt. The person may feel guilty about a specific life experience, or may feel general guilt not related to anything in particular.

If pain and self-criticism become great enough, they can lead to feelings of hopelessness, self-destructive behavior, or thoughts of death and suicide. The vast majority of people who suffer severe depression do not attempt or complete suicide, but they are more likely to do so than people who are not depressed.

Symptoms of major depression include:

People with persistent depressive disorder may have many of the same symptoms, although fewer symptoms are needed to make the diagnosis, and these symptoms are long-lasting.


A primary care physician or a mental health professional usually can diagnose depression by asking questions about a person's medical history and symptoms.

Many people with depression do not seek evaluation or treatment because of society's attitudes about depression. The person may feel the depression is his or her fault or may worry about what others will think. Also, the depression itself may distort a person's ability to recognize the problem. Therefore, family members or friends may need to encourage someone showing symptoms of depression to seek help.

There are no specific tests for depression. However, it is important to be evaluated by a primary care physician to make sure the symptoms are not being caused by a medical condition or medication.

Expected duration

On average, untreated episodes last several months. However, episodes of major depression can last any length of time. Symptoms can also vary in intensity during an episode.

If depression is not treated, it can become chronic (long-lasting). Treatment can shorten the length and severity of a depressive episode.


There is no way to prevent major depression, but detecting the first signs of depression early can help, as increasing physical activity, prioritizing sleep, and other lifestyle changes can improve symptoms. Treatment can both reduce symptoms and help to prevent the illness from returning.


The most helpful treatment is a combination of psychotherapy and medication. A medication from a class of antidepressants called selective serotonin reuptake inhibitors (SSRIs) is often prescribed first. These medications include fluoxetine (Prozac), sertraline (Zoloft), paroxetine (Paxil), citalopram (Celexa), and escitalopram (Lexapro). They are not without problems, but they are fairly easy to take and relatively safe compared with previous generations of antidepressants.

SSRIs are known to cause problems with sexual functioning, some nausea, and an increase in anxiety in the early stages of treatment.

Other effective antidepressants include bupropion (Wellbutrin), venlafaxine (Effexor), mirtazapine (Remeron), and duloxetine (Cymbalta). Two older classes of antidepressants, tricyclic antidepressants and monoamine oxidase inhibitors, are also still in use. They are as effective as the newer ones and can be very useful when someone has not responded well to other treatments.

It usually takes at least two to six weeks of taking an antidepressant to see improvement. It may take several attempts to find the medication that works best. Once the right medication is found, it may take up to a few months to find a proper dose and for the full positive effect to be seen.

Sometimes, two different antidepressants are used together. Or a mood stabilizer, such as lithium (sold under several brand names) or valproic acid (Depakene, Depakote), is added. If psychotic symptoms are present, a doctor may prescribe an antipsychotic medication. These include haloperidol (Haldol), risperidone (Risperdal), ziprasidone (Geodon), aripiprazole (Abilify), and olanzapine (Zyprexa).

A number of different psychotherapy techniques have been demonstrated to be helpful, depending on the causes of the depression, the availability of family and other social support, and an individual's personal style and preference. A technique called cognitive behavioral therapy can help a depressed person recognize negative thinking and teach techniques for controlling symptoms. Other types of therapy, including psychodynamic, insight-oriented, and interpersonal psychotherapy, can help depressed people to sort out conflicts in important relationships or explore the history behind symptoms.

If you suffer from depression, you will benefit from learning all you can about the illness. You can also make use of any support networks that may be available in your community.

Electroconvulsive therapy (ECT) can be a lifesaving option. In ECT, an electrical impulse is applied to the person's scalp and passes through to the brain, causing a seizure. The patient is under anesthesia for the entire procedure and is monitored carefully. Medication is given before the procedure to prevent any outward signs of convulsions, which helps to prevent injury. Improvement is seen gradually over a period of days to weeks after the treatment. ECT is the quickest and most effective treatment for the most severe forms of depression, and in most people, it is not any more risky than other antidepressant treatments.

Repetitive transcranial magnetic stimulation (rTMS) is another treatment for depression that is becoming more common. rTMS uses magnetic fields to alter brain function, possibly improving connections between neurons and changing how regions of the brain interact to influence mood.

Treatment options

The following list of medications are related to or used in the treatment of this condition.

View more treatment options

Antidepressants and suicide risk

Since 2004, the FDA has required manufacturers of antidepressants to include a so-called "black box warning" on their product labeling. The warning is intended to address the concern that antidepressants may increase the risk of suicide in children, adolescents, and young adults. This problem has remained a focus of research, but the evidence surrounding it remains hard to interpret.

A small number of young people taking these medications probably do have an unusual reaction and end up feeling much worse, rather than better. Any medication that affects mood can have an unexpected negative effect in some people.

However, some experts worry that this warning has had too much of a chilling effect on the use of antidepressants for treatment. It is potentially dangerous for both doctors and patients to be too cautious about using a helpful intervention. When depression goes untreated, the risk of suicide goes up. Paradoxically, it is possible that the labeling puts more people at risk for suicide if it means that some people do not receive the treatment they need.

Therefore, independent of this debate, it is always important to monitor your treatment closely. No matter what age you are or what treatment you're getting, report any troubling symptoms or worsening mood to your doctor immediately.

When to call a professional

Depression is a painful and potentially dangerous, but treatable, illness. You should contact a health care professional if you have any suspicion that you or a loved one is depressed.


Treatment of depression has become quite sophisticated and effective. The prognosis for treated depression is excellent. With treatment, the intensity of symptoms and the frequency of episodes often are significantly reduced. Many people recover completely.

When treatment is successful, it is still important to stay in close touch with your doctor or therapist, because maintenance treatment is often required to prevent depression from returning.

Additional info

National Institute of Mental Health

American Psychiatric Association

American Psychological Association

Depression and Bipolar Support Alliance (DBSA)

National Alliance on Mental Illness

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.