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.

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  • A primary mood disorder characterized by a sustained 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


6.6% from 2001 to 2002 in USA (1)

  • 16.2% lifetime risk of having major depressive disorder (1)
  • Patients can relapse; risk decreases with longer remission period but increases in patients with severe episodes, episodes at a younger age, and multiple episodes.
  • Predominant age:
    • Low risk before early teens, but highest prevalence in teens and young adults (1)
  • Predominant gender
    • Females > Males (2:1)

Etiology and Pathophysiology

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

  • 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, acetylcholine, 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.

Multiple gene loci place a person at increased risk when faced with environmental stressor; twin studies suggest 37% concordance (2).

Risk Factors

  • Female > Male (2:1)
  • 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

Commonly Associated Conditions

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

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