What is the definition of Major Depressive Disorder (MDD)?

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From the Guidelines

Major depression is a serious mood disorder characterized by persistent feelings of sadness, hopelessness, and loss of interest in activities, diagnosed when at least 5 specific symptoms are present for at least 2 weeks, representing a change from previous functioning, as defined by the American Psychiatric Association 1. The symptoms of major depression typically include:

  • Depressed mood most of the day, nearly every day
  • Markedly diminished interest or pleasure in all, or nearly all, activities most of the day, nearly every day
  • Significant weight loss or gain, or increased or decreased appetite nearly every day
  • Insomnia or hypersomnia nearly every day
  • Psychomotor agitation or retardation nearly every day
  • Fatigue or loss of energy nearly every day
  • Feelings of worthlessness or inappropriate guilt nearly every day
  • Diminished ability to think or to concentrate, or indecisiveness, nearly every day
  • Recurrent thoughts of death, recurrent suicidal ideation without a specific plan, or a suicide attempt, or a specific plan to commit suicide, as outlined in the study published in Pediatrics 1. According to a more recent study published in the Annals of Internal Medicine, major depressive disorder is the most prevalent depressive disorder, with an estimated lifetime prevalence of 16% in the United States, and is defined as depressed mood or loss of pleasure or interest along with other symptoms that last for at least 2 weeks and affect normal functioning 1. The treatment of major depression can be characterized by 3 phases: acute, continuation, and maintenance, and various treatment approaches can be used to manage MDD, such as psychotherapy, complementary and alternative medicine, exercise, and pharmacotherapy, with the goal of preventing relapse and improving quality of life 1. The most effective treatment for major depression usually combines psychotherapy, particularly cognitive behavioral therapy, with medications such as selective serotonin reuptake inhibitors (SSRIs), starting at appropriate doses and typically continuing for at least 6-12 months after symptom improvement to prevent relapse, as supported by the highest quality evidence 1.

From the FDA Drug Label

A major depressive episode implies a prominent and relatively persistent depressed or dysphoric mood that usually interferes with daily functioning (nearly every day for at least 2 weeks); it should include at least 4 of the following 8 symptoms: change in appetite, change in sleep, psychomotor agitation or retardation, loss of interest in usual activities or decrease in sexual drive, increased fatigue, feelings of guilt or worthlessness, slowed thinking or impaired concentration, and a suicide attempt or suicidal ideation.

Major depression is defined as a prominent and relatively persistent depressed or dysphoric mood that interferes with daily functioning, lasting for at least 2 weeks, and includes at least 4 of the following 8 symptoms:

  • Change in appetite
  • Change in sleep
  • Psychomotor agitation or retardation
  • Loss of interest in usual activities or decrease in sexual drive
  • Increased fatigue
  • Feelings of guilt or worthlessness
  • Slowed thinking or impaired concentration
  • A suicide attempt or suicidal ideation 2

From the Research

Definition of Major Depression

Major depressive disorder (MDD) is characterized by:

  • Persistent depressed mood
  • Loss of interest or pleasure in previously enjoyable activities
  • Recurrent thoughts of death
  • Physical and cognitive symptoms 3 It is a complex disorder that cannot be fully explained by any one single established biological or environmental pathway, but rather a combination of genetic, environmental, psychological, and biological factors 3.

Key Features

The disorder is marked by:

  • A persistent low mood
  • Anhedonia (loss of interest or pleasure in activities)
  • Feelings of worthlessness 4 These features can significantly impact an individual's quality of life, leading to reduced functional outcomes and impaired social interactions 3.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Major depressive disorder.

Nature reviews. Disease primers, 2023

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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