Depression

Depression is characterized by a sad, low or irritable mood that affects an individual’s capacity to function.^{[ Reference 1 ]} Depressive disorders are common, yet underdiagnosed and undertreated, mental health conditions that are a cause of impaired quality of life, reduced productivity, and increased mortality in the United States.^{[ Reference 2 ]} The prevalence of individuals with depression in the United States is approximately 8 percent during any two-week period,^{[ Reference 3 ]} but current rates likely underestimate the true occurrence of depressive disorders because many with depression never seek treatment.^{[ Reference 4 ]}

Depression is frequently a recurrent disorder.^{[ Reference 1 ]} Individuals with depression are at increased risk of suicide and depression is a significant independent risk factor for a number of medical conditions including first myocardial infarction and cardiovascular mortality.^{[ Reference 5 ]} There are several depressive disorders, including:^{[ Reference 1 ]}

Major depressive disorder
Persistent depressive disorder (dysthymia)
Premenstrual dysphoric disorder
Substance/medication-induced depressive disorder
Other less common depressive disorders

Service members returning from combat deployments are at increased risk for developing depression.^{[ Reference 6 ]} Research found that 7-14 percent of service members returning from Operation Enduring Freedom (OEF) and 8-15 percent of service members returning from Operation Iraqi Freedom (OIF) met the screening criteria for major depressive disorder.^{[ Reference 7 ]}

Depression is caused by a combination of genetic, biological, environmental, and psychological factors. — PHCoE graphic
^{[ Reference 6 ]} ,^{[ Reference 7 ]}

Depressive disorders are diagnosed when a persistent low mood and an absence of positive affect are accompanied by a range of symptoms, such as: ^{[ Reference 9 ]}

loss of interest in most activities (anhedonia)
fatigue or loss of energy
significant change in weight or appetite
insomnia or hypersomnia
decreased concentration
inappropriate guilt or feelings of worthlessness
psychomotor agitation or retardation
suicidal ideation

There are multiple known risk factors for developing depression, with a combination of factors resulting in an increased likelihood in the development of depression. ^{[ Reference 10 ]}

Type of Risk Factor	Characteristic/Condition
Temperamental	Neuroticism/negative affectivity: individuals with high levels are more likely to develop depressive episodes in response to stressful life events ^{[ Reference 11 ]} Cognitive factors: such as low self-esteem or perceived loss of control ^{[ Reference 12 ]}
Environmental	Adverse childhood experiences, particularly with multiple experiences ^{[ Reference 13 ]} Stressful life events: such as physical or sexual abuse, ^{[ Reference 14 ]}sexual assault, the loss of a loved one, a difficult relationship, or financial problems ^{[ Reference 15 ]} Military related: such as deployment ^{[ Reference 16 ]}
Genetic and Physiological	First-degree family members of individuals with major depressive disorder have a risk for major depressive disorder two- to fourfold higher than that of the general population ^{[ Reference 16 ]} For persistent depressive disorder, a number of brain regions (e.g., prefrontal cortex, anterior cingulate, amygdala, hippocampus) have been implicated ^{[ Reference 17 ]} Female gender: women are twice as likely as men to experience depression ^{[ Reference 18 ]}
Course Modifiers	Co-occurring physical illnesses: stroke, heart disease, cancer, Alzheimer’s disease, diabetes, chronic illness, and hormonal disorders ^{[ Reference 1 ]} Co-occurring mental disorders, such as eating disorders or anxiety disorders: all major non-mood disorders increase the risk of an individual developing depression ^{[ Reference 1 ]} Drug or alcohol abuse, to include certain medications ^{[ Reference 1 ]}

6.7% of adults ages 18 or older had a major depressive episode in 2016 (NSDUH, 2015); 12.5% of adolescents ages 12 to 17 had a major depressive episode in 2015 (NSDUH, 2015); Women are nearly 2x as likely as men to experience depression (Mayo Clinic); In the last 2 years, service members were hospitalized for depression more frequently than for anxiety, PTSD, or substance use disorders (MHS Data Repository, 2017)

Psychological Health Center of Excellence

Depression

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