Skip Navigation
NIH MedlinePlus the Magazine, Trusted Health Information from the National Institutes of Health


Understanding Depression

Dr. Carlos Zarate of the National Institute of Mental Health (right) and a colleague monitor a patient participating in research from a MEG scanner control room. MEG scans can lead to a better understanding of brain functioning.

Depression is one of the most common and serious mental disorders in the U.S. Also called major depressive disorder or clinical depression, it causes severe symptoms that affect how you feel, think, and handle daily activities, such as sleeping, eating, or working. Current research suggests that depression is caused by a combination of genetic, biological, environmental, and psychological factors.

Types of depression

Depression can present itself in a variety of forms. No two people are affected the same way by depression and there is no "one-size-fits-all" for treatment. To be diagnosed with depression, the symptoms must be present for at least two weeks. It may take some trial and error to find the treatment that works best for you.

The major categories are:

  • Persistent depressive disorder is a depressed mood that lasts for at least two years.
  • Perinatal depression is much more serious than the "baby blues," relatively mild depressive and anxiety symptoms that typically clear within two weeks after giving birth. Women with perinatal depression experience full-blown major depression during pregnancy or after delivery (postpartum depression).
  • Psychotic depression occurs when a person has severe depression plus some form of psychosis, such as having delusions or hallucinations.
  • Seasonal affective disorder (SAD) is characterized by the onset of depression during the winter, when there is less sunlight.
  • Bipolar disorder is different from depression, but it is included in this list because someone with bipolar disorder experiences episodes of extremely low moods that meet the criteria for major depression (called "bipolar depression"). But a person with bipolar disorder also experiences extreme high—euphoric or irritable—moods called "mania" or a less severe form called "hypomania."

Signs and symptoms

If you have been experiencing some of the following signs and symptoms most of the day, nearly every day, for at least two weeks, you may be suffering from depression. The signs and symptoms include the following.

  • Persistent sad, anxious, or "empty" mood
  • Feelings of hopelessness, or pessimism
  • Feelings of guilt, worthlessness, or helplessness
  • Loss of interest or pleasure in hobbies and activities
  • Difficulty concentrating, remembering, or making decisions
  • Difficulty sleeping, early-morning awakening, or oversleeping
  • Thoughts of death or suicide, or suicide attempts

Treatment and Therapies

Depression, even the most severe cases, can be treated. The earlier treatment can begin, the more effective it is. Depression is usually treated with medications, psychotherapy, or a combination of the two. If these treatments do not reduce symptoms, electroconvulsive therapy (ECT) and other brain stimulation therapies may be options to explore.


Antidepressants are medicines that treat depression. They may help improve the way your brain uses certain chemicals that control mood or stress. You may need to try several different antidepressant medicines before finding the one or ones that improve your symptoms and have manageable side effects.

Antidepressants take time—usually two to four weeks—to work, and often, symptoms such as sleep, appetite, and concentration problems improve before mood lifts.

Research Update

Big Data Can Guide Psychiatric Treatment

NIH grantee Dr. Roy Perlis at Massachusetts General Hospital is pursuing innovative research using data science to find new treatments for depression.

Pooling large amounts of data from electronic health records, doctor's medical notes, and simple surveys, the data are added to existing knowledge about which genes may predict patients at risk for developing depression. Dr. Perlis and his collaborators found they could make better predictions about discharged hospitalized patients who would benefit from a range of possible interventions, such as medication, occupational therapy, or a phone call or web-based follow-up for lower-risk patients.

This novel research approach is seen as a complement to large scale clinical studies, and has the promise to save time and money, and to benefit patients. It is an example of what NIH seeks to accomplish with its new "All of Us" Research Program Opens new window (www.

Find Out More

Mental Health Institute Seeks Speedier Depression Relief

Rapidly-Acting Treatments for Treatment-Resistant Depression (RAPID) is an NIMH-funded research project that promotes development of speedier therapies for severe, treatment-resistant depression. The initiative is supporting researchers, led by Maurizio Fava, MD, of Massachusetts General Hospital, who are identifying and testing promising treatments that lift depression within a few days.

By contrast, current antidepressant medications usually take a few weeks to work—and half of patients fail to fully respond. While a proven brain stimulation technique, electroconvulsive therapy (ECT), works faster, it runs a risk of cognitive side-effects and requires anesthesia and a surgical setting. The urgent need for improved, faster acting antidepressant treatments is underscored by the fact that severe depression can be life-threatening, due to heightened risk of suicide.

Recent research provides clues to potential fast-acting antidepressant brain mechanisms, and the RAPID team is collaborating with investigators in NIMH's Intramural Research Program, who have pioneered studies of fast-acting antidepressant mechanisms in trials of ketamine and scopolamine. The project aims to translate such evidence into practical treatments.

Read More "Depression" Articles

Dealing with Depression / Depression Strikes… Anyone / For the First Time, Life Seems Worth Living | Dr. Carlos Zarate / Understanding Depression | Research Update

Winter 2017 Issue: Volume 11 Number 4 Page 7-8