Depression was found in 5-Minute Clinical Consult which helps you diagnose, treat, and follow up on over 900 medical conditions seen in everyday practice.

To view this entire topic, please or purchase a subscription.

Explore 5-Minute Clinical Consult - view these FREE monographs:

5-Minute Clinical Consult

-- The first section of this topic is shown below --



  • A primary mood disorder characterized by a depressed mood and/or decreased interest in things that used to give pleasure (anhedonia), which represents a change from previous functioning
  • Synonym(s): Unipolar affective disorder, Major depressive disorder
  • System(s) affected: Nervous


Affects >18 million in the US

  • 13–16% lifetime risk of having major depressive disorder (MDD)
  • Recurrence in 50–80% of cases, usually within 2–3 years; risk increases by 16% with each episode

Risk Factors

  • Female > Male (2:1)
  • Elderly (≥65), although 1st onset usually in 20s
  • Severity of 1st episode
  • Persistent sleep disturbances
  • Presence of chronic disease(s), recent myocardial infarction (MI), cardiovascular accident (CVA)
  • Strong family history (depression, bipolar, suicide, substance abuse), spouse with depression
  • Substance abuse and dependence, domestic abuse/violence
  • Losses, stressors, unemployment
  • Single, divorced, or unhappily married

Multiple gene loci place a person at increased risk when faced with environmental stressor; twin studies suggest 37% concordance (1)


Complex etiology with 2 major models in the literature (1):

  • Monoamine-Deficiency Hypothesis: Symptoms related to decreased levels of norepinephrine (dullness and lethargy) and serotonin (irritability, hostility, and suicidal ideation) in multiple regions of the brain; other neurotransmitters involved include dopamine, acetlycholine, γ-aminobutyric acid (GABA), glutamate.
  • Stress/Hypothalamic-Pituitary-Adrenal Axis: Abnormalities in cortisol response lead to depression; elevated cortisol levels can be associated with depression, but cortisol tests are not indicated for diagnosis.
  • Other areas of research interest: Inflammatory processes and abnormal circadian rhythms


  • Impaired synthesis/metabolism of neurotransmitters
  • Environmental factors and learned behavior may affect neurotransmitters and/or have an independent influence on depression.

Commonly Associated Conditions

  • Bipolar disorder, cyclothymic disorder, grief reaction, anxiety disorders, schizophrenia/schizoaffective disorders
  • Medical comorbidity
  • Substance abuse

-- To view the remaining sections of this topic, please or purchase a subscription --