Depression is a mental state of low mood and aversion to activity.[3] It affects about 3.5% of the global population, or about 280 million people worldwide, as of 2020.[4] Depression affects a person's thoughts, behavior, feelings, and sense of well-being.[5] The pleasure or joy that a person gets from certain experiences is reduced, and the afflicted person often experiences a loss of motivation or interest in those activities.[6] People with depression may experience sadness, feelings of dejection or hopelessness, difficulty in thinking and concentration, or a significant change in appetite or time spent sleeping; suicidal thoughts can also be experienced.
Depression can have multiple, sometimes overlapping, origins. Depression can be a symptom of some mood disorders, some of which are also commonly called depression, such as major depressive disorder, bipolar disorder and dysthymia.[7] Additionally, depression can be a normal temporary reaction to life events, such as the loss of a loved one. Depression is also a symptom of some physical diseases and a side effect of some drugs and medical treatments.
Life events
Adversity in childhood, such as bereavement, neglect, mental abuse, physical abuse, sexual abuse, or unequal parental treatment of siblings, can contribute to depression in adulthood.[8][9] Childhood physical or sexual abuse in particular significantly correlates with the likelihood of experiencing depression over the survivor's lifetime.[10] People who have experienced four or more adverse childhood experiences are 3.2 to 4.0 times more likely to suffer from depression.[11] Poor housing quality, non-functionality, lack of green spaces, and exposure to noise and air pollution are linked to depressive moods, emphasizing the need for consideration in planning to prevent such outcomes.[12] Locality has also been linked to depression and other negative moods. The rate of depression among those who reside in large urban areas is shown to be lower than those who do not.[13] Likewise, those from smaller towns and rural areas tend to have higher rates of depression, anxiety, and psychological unwellness.
Studies have consistently shown that physicians have had the highest depression and suicide rates compared to people in many other lines of work—for suicide, 40% higher for male physicians and 130% higher for female physicians.
Childhood and adolescence
Depression in childhood and adolescence is similar to adult major depressive disorder, although young sufferers may exhibit increased irritability or behavioral dyscontrol instead of the more common sad, empty, or hopeless feelings seen with adults.[25] Children who are under stress, experiencing loss, or have other underlying disorders are at a higher risk for depression. Childhood depression is often comorbid with mental disorders outside of other mood disorders; most commonly anxiety disorder and conduct disorder. Depression also tends to run in families.
