Depression is a common mental health disorder characterized by sadness, lethargy, and loss of interest in daily life activities. Read the overview below to gain an understanding of this illness and explore the previews of other articles examining different aspects of depression.

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Depression Topic Overview

"Watson, Stephanie. "Depression." Gale Health and Wellness Online Collection, Gale, 2021. 

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Depression is a mood disorder that causes persistent feelings of sadness, hopelessness, loss of interest, and decreased energy. A diagnosis of major depression means symptoms have been consistent nearly every day for at least two weeks. However, depression is more than just unhappiness. It can be severe enough to interfere with relationships, work, school, and other daily activities. Doctors also refer to this condition as major depressive disorder or clinical depression.

An estimated 1 in 6 people, or nearly 17 percent of Americans, will experience depression at some point in their lifetime, according to the American Psychiatric Association. About 7 percent of Americans have at least one major depressive episode per year. Although the symptoms can start at any age, depression is most likely to begin during a person's teens or 20s.


Types of depression
  • Along with major depression, there are several other types of depression, which are characterized by their symptoms or causes: Postpartum depression involves feelings of extreme sadness, fatigue, and anxiety that start after a woman gives birth.
  • Premenstrual dysphoric disorder (PMDD) is severe depression, irritability, and anxiety that occurs in the week or two before a woman's period.
  • Seasonal affective disorder (SAD) is depression that occurs during the winter months and is relieved by the change of season.
  • Bipolar disorder, formerly called manic depression, is characterized by alternating episodes of extremely low mood (depression) and exuberant highs (mania).
  • Persistent depressive disorder, which is depressions lasting two years or more. It combines dysthymia, which is a low-grade but persistent depression with chronic major depression. People with persistent depressive disorder generally lack energy, have low self-esteem, and often feel helpless.
  • Psychotic depression includes features of both depression and psychosis, such as having false beliefs (delusions) or seeing and hearing things that are not there (hallucinations).

Depression stems from a combination of biological, environmental, and psychological factors. People with depression often have family members with the condition, which suggests that genetics are involved. If one biological twin has depression, the other twin has a 70 percent chance of also having the condition.

Researchers have discovered differences in the brains of people with depression, as well as in the function of chemical messengers called neurotransmitters. Hormonal changes also can set off depressive symptoms; for example, during a woman's menstrual cycle or after she gives birth.

The following factors increase the risk for depression:

  • a personal or family history of depression or other mental health disorder
  • trauma or stress, such as physical or sexual abuse, relationship issues, or financial worries drug or alcohol abuse
  • medical conditions such as diabetes, cancer, heart disease, stroke, and Parkinson's disease certain medications, including those used to treat high blood pressure and insomnia



People who have depression will experience some or all of the following symptoms (almost every day for at least two weeks for major depression):

  • Persistent sad or empty mood
  • Feelings of hopelessness, helplessness, emptiness, worthlessness, or guilt
  • Low energy, fatigue
  • Irritability, restlessness, anxiety
  • Slowed thinking, speaking, or movement
  • Loss of interest in activities they once enjoyed
  • Trouble concentrating, remembering, or making decisions
  • Loss of appetite, or eating too much
  • Weight gain or loss
  • Trouble sleeping, or sleeping too much
  • Headache, stomachache, and other aches and pains that do not have a clear physical cause
  • Thoughts of death or suicide

Some people with depression will experience many of these symptoms. Others will have just a few. The severity of depression symptoms can range from mild to severe enough to affect a person's day-to-day life.


Doctors start the diagnostic process with a physical exam and lab work to rule out possible physical causes of depression, such as a thyroid disorder or vitamin deficiency. A psychologist or physician can do a psychological evaluation, asking questions and assessing symptoms according to established criteria for identifying depression and arriving at a diagnosis.



Since chemistry in the brain is linked to depression, a person might take an antidepressant, which can modify the brain's chemistry. Typical treatment includes antidepressants or other medications, psychotherapy (talk therapy), or a combination of the two interventions. Personalizing treatment to the individual can increase the chances that it will be successful.

Antidepressants are a class of drugs used to treat depression. They include the following types:

  • Selective serotonin reuptake inhibitors (SSRIs) are often the first drugs doctors prescribe for depression. These drugs affect the chemical messenger, serotonin, which helps to regulate mood. Low serotonin levels have been linked to depression. Serotonin-norepinephrine reuptake inhibitors (SNRIs) work on two brain chemicals—serotonin and norepinephrine.
  • Atypical antidepressants act on the brain in a different way from other antidepressants. These drugs may be an option for people who have not found relief from SSRIs or SNRIs.
  • Tricyclic antidepressants are an older class of antidepressant. They work on three brain chemicals: serotonin, norepinephrine, and dopamine. Tricyclics are not used as often as they once were because they have a higher risk for side effects than newer antidepressants.
  • Monoamine oxidase inhibitors (MAOIs), the first class of antidepressants developed, are used infrequently today due to their numerous interactions with other drugs and foods.
  • In 2019, the FDA approved a nasal spray called esketamine (Spravato) to treat people with major depression and for whom other antidepressants are not working. The spray works more quickly than do SSRIs taken by mouth.

Sometimes doctors will prescribe another type of medication—such as an anti-anxiety drug, antipsychotic medicine, or stimulant—along with the antidepressant. Antidepressants can take up to four weeks to achieve their full benefits. Other drugs might work specifically for one type of depression. For example, brexanolone became the first therapy approved (in 2019) for treating postpartum depression specifically. It can take a few tries to find the best drug and dosage combination that will relieve your depression.

Talk therapy programs like cognitive-behavioral therapy (CBT) help people with depression identify the negative thoughts and behaviors that result from depression, and replace them with more positive strategies for building coping skills and psychological resilience. Therapy can be done one-on-one with a therapist, as part of a group, or together with a partner or other family members.

If these treatments are not effective, brain stimulation therapies including electroconvulsive therapy (ECT) might be an option. ECT is done while a person is under general anesthesia. Small electrical currents are passed through the brain to induce a seizure. Research finds ECT is often effective in cases where antidepressants and talk therapy fail.

A few alternative remedies and supplements are used to treat depression, including acupuncture, meditation, guided imagery, and tai chi. Evidence that herbal supplements like St. John's wort and SAMe help with depression symptoms is inconclusive, and they are

not FDA-approved treatments. Because these supplements can often cause side effects or interact with other medications you take, alert your doctor first if you would like to try them.



Depression is highly treatable. Up to 90 percent of people will eventually improve with medication, therapy, a combination of the two, or another treatment. However, it can take some trial and error to find the therapy that works best. Help is available for people who are struggling with depression through the U.S. Substance Abuse and Mental Health Services Administration (SAMHSA) helpline at 1-800-662-HELP (4357).

Suicidal thoughts and actions can occur in people who are severely depressed. Anyone who might be considering harming themselves should call a trusted health care provider right away, reach out to supportive friends or family members, or call the National Suicide Prevention Lifeline at 1-800-273-TALK (1-800-273-8255). If a friend or loved one is at immediate risk for self-harm, it is advised to dial 911 or local emergency services.




"Depression." MedlinePlus. October 28, 2020. (accessed November 16, 2020). "Depression." National Institute of Mental Health. February 2018. (accessed November 16, 2020).

"Depression (major depressive disorder)." Mayo Clinic. February 3, 2018. (accessed November 16, 2020).

"Major Depression in Teens." Health Encyclopedia, University of Rochester Medical Center. (accessed November 16, 2020).

"What Is Depression?" American Psychiatric Association. October 2020. families/depression/what-is depression (accessed November 16, 2020).



American Psychiatric Association,   800 Maine Avenue, S.W., Suite 900,   Washington,   D.C.,   20024 (888) 357-7924,   (202) 559

National Alliance on Mental Illness (NAMI),   3803 N. Fairfax Drive, Suite 100,   Arlington,   VA,   22203,  (800) 950-6264,   (703) 524

National Institute of Mental Health,   6001 Executive Boulevard, Room 6200,  Bethesda,   MD,   20892-9663,   (866) 615-6464,   Fax 443-4279,   [email protected],

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Depressive Disorders

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Source: "Academy of American Family Physicians, Disclaimer: This information is not a tool for self-diagnosis or a substitute for professional care. This image may be used for personal, non-commercial purposes only.

"Depressive Disorders." The Gale Encyclopedia of Children's Health: Infancy through Adolescence, edited by Deirdre S. Blanchfield, 3rd ed., vol. 2, Gale Health and Wellness, Gale, 2016,

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