Depression Centers for Disease Control and Prevention (CDC, 2013a) reported that in 2005/2006 an estimated 5.4% of all Americans over the age of 12 sought medical help for depression. Americans, however, are far from alone. Globally, 37% of lost life years due to disease have been attributed to mental illness (Insel, 2011). Of this 37%, depression is responsible for a full third. The economic burden of mental illness on a global scale is massive, representing $2.5 trillion dollars in 2010. By comparison, all health care spending worldwide in 2009 reached $5.1 trillion. These statistics suggest mental illness accounts for half of all health care spending globally and depression is responsible for approximately one-third. In addition, mental illness is expected to account for 35% of lost economic output within two decades. Given the substantial impact that depression has on society and the lives of individuals, this essay will review what is known about depression, its symptoms, how it is diagnosed and treated, and what can be done to prevent depressive episodes.

Who Gets Depression?

The greatest levels of depression were experienced by middle-aged Americans (7.3%), but between 4 and 5% of everyone else over the age of 12 also reported depressive symptoms (CDC, 2013b). Being female increased the risk for depression by 67.5%, but 4% of all males will experience depression as well. The prevalence of depression can be stratified by race and ethnicity, with depression afflicting 8% of African-Americans, 6.3% of Mexican-Americans, and 4.8% of Whites.

What is Depression?

A clinical depression of diagnosis in Western society has historically relied on the diagnostic criteria published by the American Psychiatric Association (APA) (CDC, 2013a); however, it is impractical for primary care physicians and nurses to use the Diagnostic and Statistical Manual (DSM) to screen patients for depression. Doctors and nurses will generally look for persistent sadness, lost of interest in rewarding and pleasurable activities, changes in weight, chronic tiredness, cognitive impairment, and suicidal ideation. While many people will have a bad day, feel sad for a few days, or find it hard to get out of bed in the mornings, depression becomes an important health issue only when the symptoms impair the ability of the patient to engage fully in their lives for weeks at a time. Accordingly, family members, friends, employers, and colleagues...

Marriages can be strained, employment threatened, and the financial and emotional well-being of the affected families undermined. Depression is also a major risk factor for suicide.
A large number of research studies have uncovered several risk factors for depression, including female gender, chronic stress, chronic pain, family history of depression, under-employed, unemployed, chronic illness, poor self-esteem, living alone, poor social support, and brain injury (Maurer, 2012). The prevalence of depression in society therefore depends on contributions from both environmental and genetic factors. This would explain why individual responses to antidepressant medications vary widely, which in turn suggests that the brains of persons suffering from major depression have incurred equally diverse changes (Keers & Uher, 2012). Genetic and psychosocial studies have revealed that stressful life events are one of the strongest predictors of depression, even events that occurred long ago during childhood. Gene by environment studies have revealed that the serotonin transport system, factors involved in neurogenesis, and the activity of the hypothalamic-pituitary-adrenal axis are probably the main contributors to depression susceptibility. This partly explains why selective serotonin reuptake inhibitors (SSRIs), the newest generation of antidepressants, have proven to be an effective medical intervention for some patients, but not all.

Screening for Depression

The U.S. Preventive Services Task Force recommends depression screening for adults and adolescents (Maurer, 2012). This recommendation is based on the findings from several studies showing that treatment with antidepressants and/or psychotherapy improves the health outcomes of adolescent and adult patients when compared to no treatment. Screening for depression in children between the ages of 7 and 11 is neither recommended nor contraindicated and there is insufficient evidence supporting the efficacy of antidepressant use in children.

There are a number of screening tools that have proven effective for both adolescents and adults and the Task Force recommends using whichever is most convenient in the clinical setting (Maurer, 2012). The Becks Depression Inventory and Zung Depression Scale are common instruments, but the Patient Health Questionnaire-2 (PHQ-2) is much shorter and equally…