The Course of Major Depression

Brindusa Vanta, MD, DHMHS
Medical editor

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To diagnose someone with major depressive disorder (MDD), the person must have had at least one major depressive episode (in which they suffer from a depressed mood or the loss of interest or pleasure in nearly all activities) for at least two weeks.[1],[2]


In addition, depressive symptoms must persist for most of the day, nearly every day, and cause problems in social interactions, work, or someone's ability to function in daily life. For some individuals with milder depressive episodes, social and occupational functioning may appear normal, but the affected person is making a serious, concerted effort to appear unimpaired.[1],[2]

When a person has experienced only one episode of depression, it is classified as major depression, single episode. When multiple major depressive episodes occur in a row, and no manic or mixed episodes are observed, the diagnosis changes to major depression, recurrent.[1],[2]

What is Recurrent vs. Single Episode Depression?

Recurrent major depressive disorder means a person has a history of two or more major depressive episodes. Meanwhile, single-episode depression involves one major depressive episode lasting at least two weeks.[1] Distinguishing between single-episode depression and recurrent-episode depression is essential for treatment as it influences the duration and intensity of therapy. Recurrent episodes typically require longer-term treatment and more comprehensive relapse prevention strategies.

How Long Does a Major Depressive Episode Last?

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Untreated, a major depressive episode may last several months. With antidepressant treatment, the episodes may be shorter. Some people only experience a single depressive episode and, after that, are symptom-free.

However, many people who experience one major depressive episode will go on to experience multiple major depressive episodes. The more major depressive episodes an individual experiences, the more likely they are to develop future episodes.

Recurrence in major depressive disorder is common, with over 50% experiencing additional episodes after recovering from the first episode. Around 80% of individuals with a history of two episodes will experience another recurrence.[6]

The course of recurrent major depression varies across individuals. Some people have isolated depressive episodes that are separated by many years during which mood is normal, while other individuals experience clusters of major depressive episodes that occur closely together in time. Still, other people with major depressive disorder experience increasingly frequent episodes as they grow older.

Prevalence and Risk of Recurrence

Factors that may increase the risk of recurrence:[3],[5]

  • Presence of co-occurring disorders, such as substance use disorders or anxiety disorders
  • Inadequate or incomplete treatment of the initial depressive episode
  • Environmental stressors like major life events
  • Biological factors like neurochemical imbalances and genetic predispositions

As Dr. Brindusa Vanta, MD, says, "Some individuals with recurrent depression may not find relief from standard treatments (antidepressants and psychotherapy). Alternative interventions like low-dose ketamine therapy, transcranial magnetic stimulation (TMS), or neurofeedback therapy may be recommended in these cases."

Triggers or Causes of Major Depressive Episodes

Highly stressful events can trigger episodes of major depression. Stressors capable of triggering major depression may include the death of a loved one and other significant losses, such as a job layoff, or relationship difficulties, such as divorce or separation.

Even normal developmental milestones, such as puberty, marriage, or retirement, may trigger depression when a particular event is personally distressing to a given individual. Stressors that trigger depression may be fresh, or they may be past events that are intensely remembered for some reason or another. For example, thinking deeply about stressful past experiences, such as emotional, physical, or sexual abuse, can be sufficient to trigger an onset of depression.

Individuals with post-traumatic stress disorder (PTSD) who have experienced a traumatic event such as a military battle, rape, severe automobile accident, or natural disaster are more likely to suffer from depression than people who have not experienced such trauma.

A wide range of medical conditions and medications can also cause or worsen MDD. Major depression frequently co-occurs with other mental illnesses such as substance-related disorders, panic disorder, obsessive-compulsive disorder, anorexia nervosa, bulimia nervosa, or borderline personality disorder.[2]

Symptoms and Diagnosis

Single episodes and recurrent episodes of major depressive disorder share many symptoms because the episodes themselves are indistinguishable. In addition to depressed mood, other symptoms experienced during MDD include [1],[2],[3],[4]

  • Thoughts of suicide or death
  • Issues concentrating or making decisions
  • Feeling guilty or worthless
  • Severe fatigue or loss of energy
  • Sleeping too much or too little
  • Loss of interest in previously enjoyed hobbies

The above symptoms must be present for at least two weeks and must cause distress and impaired functioning. If someone has single-episode depression, they will only experience one depressive episode. Conversely, recurrent-episode depression involves more than one depressive episode.

Diagnosing MDD

At present, there is no diagnostic laboratory test (e.g., no blood test) that can confirm whether you have major depression. However, some laboratory tests can appear abnormal during an active depressive episode.

For example, sleep electroencephalograph (measurements of electrical activity in the brain during sleep) abnormalities have been found in many individuals who are hospitalized for MDD. Even depressed people who do not have symptoms severe enough to require hospitalization may show EEG abnormalities.

As Dr. Brindusa Vanta, MD, says, "PET scans are used in research studies to detect depression. These brain scans may show changes in brain activity and metabolism associated with the condition."

Even though lab tests aren't used to diagnose depression, don't be surprised if your doctor still sends you to the lab. Medical tests can be helpful in ruling out other conditions that may cause depressive moods, such as thyroid trouble, cancer, or arthritis.

Symptoms of Major Depressive Disorder

Symptoms of major depressive disorder usually develop over a few days or weeks.

Many people feel anxious or mildly depressed for a while before a full depressive episode becomes apparent. Often, the symptoms eventually disappear, and functioning returns to normal. The DSM-5 provides labels that describe the course of a person's major depression. "Full remission" means no current depressive symptoms; "partial remission" means that the person currently has fewer than five depressive symptoms or has had no symptoms at all for less than two months; and "chronic" means that a person has met all of the diagnostic criteria for major depression for two or more years. 

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  1. World Health Organization. (2023). Depressive disorder (depression). Retrieved from
  2. American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.).
  3. American Psychiatric Association. (2020). What is depression? Retrieved from
  4. Bains N, Abdijadid S. Major Depressive Disorder. [Updated 2023 Apr 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from:
  5. Bockting, C. L., Hollon, S. D., Jarrett, R. B., Kuyken, W., & Dobson, K. (2015). A lifetime approach to major depressive disorder: The contributions of psychological interventions in preventing relapse and recurrence. Clinical psychology review, 41, 16–26.
  6. Burcusa, S. L., & Iacono, W. G. (2007). Risk for recurrence in depression. Clinical psychology review, 27(8), 959–985.

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