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Depression is a clinical diagnosis characterized by ≥2 weeks of depressed mood and/or anhedonia (lack of interest in pleasure) and multiple additional symptoms:

  • Change in appetite (or weight change)

  • Change in sleep pattern

  • Change in activity

  • Fatigue and/or loss of energy

  • Guilt and/or feeling of worthlessness

  • Diminished concentration

  • Suicidal thoughts

Anxiety symptoms are common among depressed individuals. Among older adults, cognitive impairment may be associated with depression. Within various cultures, depression can manifest with more somatic symptoms rather than mood symptoms.


Mental health is essential and integral to overall health. Due to stigma of mental illness, the perceived gap between physical and mental health has increased. As a result, individuals are reluctant to report mental health symptoms and seek specialized treatment. In addition, some demographic groups are also at higher risk for having unmet mental health needs, including children and youth, older adults, and members of medically underserved ethnic and racial groups. Because these groups are most likely to be evaluated in primary care settings, it is essential that primary care physicians and other allied health practitioners are equipped to provide high-quality mental health services.

Depression is one of the leading causes of disability worldwide. By the year 2030, it is projected to be the leading cause of overall disease burden in high-income countries. It is a highly prevalent condition, affecting 35% of patients seen in primary care settings, and its prevalence in all age groups has been increasing in recent years. The most common age of onset is between 25 and 35 years old, and an earlier age of onset of depression is associated with worse prognosis and functional impairment over time. Depression is twice as common among women as men, and black and Hispanic individuals with a diagnosis of depression are less likely to receive mental health services compared to their white counterparts. In addition, older adults are less likely to receive mental health services compared to younger adults.

Depression is a highly comorbid condition, particularly in later life. Medical illness and disability, which are more common in the elderly, are risk factors for depression. Depression diminishes quality of life, leads to nonadherence with self-care and treatment recommendations, increases the use of medical services, and is associated with cognitive impairment in adults. Furthermore, depression is often associated with medical and social complexity; patients with depression often have multiple chronic conditions, poor socioeconomic status, and poor social support, which in turn increase the risk of developing depression. Additionally, major psychosocial risk factors for depression include bereavement, caregiver strain, social isolation, disability, chronic medical illness, and role transitions.

Agency for Healthcare Research and Quality. 2016 National Healthcare Quality and Disparities Report. Rockville, MD: Agendcy for Healthcare Research and Quality; 2017.
González  HM, Vega  WA, Williams  DR, Tarraf  W, West  BT, Neighbors ...

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