Description

A primary mood disorder characterized by a sustained feeling of sadness and/or decreased interest in all or most activities once enjoyed (anhedonia), which represents a change from previous functioning

Epidemiology

Incidence

• In the United States, 8.1% of adults age ≥20 years experienced depression in a given 2-week period between 2013 and 2016.
• 19.2% lifetime risk of having major depressive disorder (MDD)

Prevalence

• Non-Hispanic Asian adults had the lowest prevalence of depression (3.1%) compared with Hispanic (8.2%), non-Hispanic white (7.9%), and non-Hispanic black (9.2%) adults. This pattern was observed among both men and women.
• Among all race and Hispanic-origin groups (except non-Hispanic Asian), men had a significantly lower prevalence of depression compared with women.
• Prevalence decreases with increasing levels of family income for both men and women.
• Predominant age: low risk before early teens but highest prevalence in teens and young adults

Etiology and Pathophysiology

There are diverse theories regarding the pathophysiology; none proven

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

Risk Factors

• Female > male (2:1)
• Severity of first 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
• Childhood trauma/maltreatment
• 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