What is Major Depressive Disorder?
Major depressive disorder, also known as clinical depression or major depression, is a mental health condition. Major depressive disorder affects millions of people worldwide. It is a serious illness that causes persistent feelings of sadness, hopelessness, and loss of interest in activities that were once enjoyable.
What are the Symptoms of Major Depressive Disorder?
The symptoms of major depressive disorder can vary from person to person, but common symptoms include:
- Persistent feelings of sadness, anxiety, or hopelessness
- Loss of interest in activities that were once enjoyable
- Changes in appetite and weight
- Difficulty sleeping or oversleeping
- Fatigue or loss of energy
- Feelings of worthlessness or guilt
- Difficulty concentrating or making decisions
- Thoughts of suicide or self-harm
To be diagnosed with major depressive disorder, a person must experience at least five of these symptoms for at least two weeks.
How is Major Depressive Disorder Diagnosed?
The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), is used by mental health professionals to diagnose major depressive disorder. The DSM-5 outlines specific criteria that must be met for a diagnosis of major depressive disorder, including the presence of specific symptoms and the duration of those symptoms.
What are the Causes of Major Depressive Disorder?
The exact cause of major depressive disorder is unknown, but it is believed to be a combination of genetic, environmental, and biological factors. Some risk factors for major depressive disorder include:
- Family history of depression
- Trauma or stressful life events
- Chronic illness or pain
- Substance abuse
- Imbalances in brain chemicals
How is Major Depressive Disorder Treated?
Treatment for major depressive disorder may include a combination of medication, therapy, and lifestyle changes. Antidepressant medications can help balance brain chemicals and improve symptoms. Therapy, such as cognitive-behavioral therapy, can help individuals learn coping skills and develop a more positive outlook. Lifestyle changes, such as regular exercise and a healthy diet, can also help improve symptoms of major depressive disorder.
If you are experiencing symptoms of major depressive disorder, it is important to seek help from a mental health professional. With the right treatment, it is possible to manage symptoms and improve your quality of life.
What is the Prevalence of Major Depressive Disorder?
Prevalence estimates depend on what is measured, the population and the survey year. The figures below describe a major depressive episode in the past year in the 2021 U.S. National Survey on Drug Use and Health, as reported by NIMH. They are historical estimates, not current-year counts of everyone with a diagnosed disorder.
| Population | Measure | Estimate | Share of that population |
|---|---|---|---|
| Adults aged 18+ | At least one major depressive episode | 21.0 million | 8.3% |
| Adults aged 18+ | Episode with severe impairment | 14.5 million | 5.7% |
| Adolescents aged 12–17 | At least one major depressive episode | 5.0 million | 20.1% |
The severe-impairment figure is a subset, not the total prevalence. Survey estimates of an episode are also different from counting people with a clinician-confirmed MDD diagnosis.
Demographics and Major Depressive Disorder
Comparisons by age, sex or race require the same survey, measure and denominator. Figures for all mental illnesses, state-level estimates and severe-impairment subsets cannot be substituted for MDD prevalence. Consult the linked NIMH tables for definitions and sampling limitations.
Living with Major Depressive Disorder
Statistics describe populations; they do not measure how serious one person’s symptoms are. If symptoms affect sleep, concentration, relationships or daily responsibilities, seek an assessment. Care may include psychotherapy, medication and support tailored to individual needs.
If there is immediate danger or thoughts of self-harm, seek urgent help from emergency services or a qualified crisis service. Do not wait for a routine admissions appointment.
