Depression is a mental state of low mood and aversion to activity. It affects more than 280 million people of all ages (about 3.5% of the global population). Depression affects a person's thoughts, behavior, feelings, and sense of well-being. Depressed people often experience loss of motivation or interest in, or reduced pleasure or joy from, experiences that would normally bring them pleasure or joy. Depressed mood is a symptom of some mood disorders such as major depressive disorder and dysthymia; it is a normal temporary reaction to life events, such as the loss of a loved one; and it is also a symptom of some physical diseases and a side effect of some drugs and medical treatments. It may feature sadness, difficulty in thinking and concentration and a significant increase or decrease in appetite and time spent sleeping. People experiencing depression may have feelings of dejection or hopelessness and may experience suicidal thoughts. It can either be short term or long term. Adversity in childhood, such as bereavement, neglect, mental abuse, physical abuse, ###ual abuse, or unequal parental treatment of siblings can contribute to depression in adulthood. Childhood physical or ###ual abuse in particular significantly correlates with the likelihood of experiencing depression over the survivor's lifetime. Should you have experienced four or more childhood adverse experiences, you're 3.0 to 4.4 times more likely to suffer from depression. 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. Life events and changes that may cause depressed mood include (but are not limited to): childbirth, menopause, financial difficulties, unemployment, stress (such as from work, education, military service, family, living conditions, marriage, etc.), a medical diagnosis (cancer, HIV, diabetes, etc.), bullying, loss of a loved one, natural disasters, social isolation, ####, relationship troubles, jealousy, separation, or catastrophic injury. Adolescents may be especially prone to experiencing a depressed mood following social rejection, peer pressure, or bullying. 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. 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. Depression is associated with low extraversion, and people who have high levels of neuroticism are more likely to experience depressive symptoms and are more likely to receive a diagnosis of a depressive disorder. It is possible that some early-generation beta-blockers induce depression in some patients, though the evidence for this is weak and conflicting. There is strong evidence for a link between alpha interferon therapy and depression. One study found that a third of alpha interferon-treated patients had developed depression after three months of treatment. (Beta interferon therapy appears to have no effect on rates of depression.) There is moderately strong evidence that finasteride when used in the treatment of alopecia increases depressive symptoms in some patients. Evidence linking isotretinoin, an acne treatment, to depression is strong. Other medicines that seem to increase the risk of depression include anticonvulsants, antimigraine drugs, antipsychotics and hormonal agents such as gonadotropin-releasing hormone agonist. Depressed mood can result from the onset of various diseases or nutritional deficiencies. People with chronic pain may also have symptoms of depression A number of psychiatric syndromes feature depressed mood as a main symptom. The mood disorders are a group of disorders considered to be primary disturbances of mood. These include major depressive disorder (commonly called major depression or clinical depression) where a person has at least two weeks of depressed mood or a loss of interest or pleasure in nearly all activities; and dysthymia, a state of chronic depressed mood, the symptoms of which do not meet the severity of a major depressive episode. Another mood disorder, bipolar disorder, features one or more episodes of abnormally elevated mood, cognition, and energy levels, but may also involve one or more episodes of depression. When the course of depressive episodes follows a seasonal pattern, the disorder (major depressive disorder, bipolar disorder, etc.) may be described as a seasonal affective disorder. Outside the mood disorders: borderline personality disorder often features an extremely intense depressive mood; adjustment disorder with depressed mood is a psychological response to an identifiable event or stressor, in which the resulting emotional or behavioral symptoms are significant but do not meet the criteria for a major depressive episode; and posttraumatic stress disorder, a mental disorder that sometimes follows trauma, is commonly accompanied by depressed mood. There is evidence for a link between inflammation and depression. Inflammatory processes can be triggered by negative cognitions or their consequences, such as stress, violence, or deprivation. Thus, negative cognitions can cause inflammation that can, in turn, lead to depression. [dubious – discuss] In addition, there is increasing evidence that inflammation can cause depression because of the increase of cytokines, setting the brain into a "sickness mode". Classical symptoms of being physically sick, such as lethargy, show a large overlap in behaviors that characterize depression. Levels of cytokines tend to increase sharply during the depressive episodes of people with bipolar disorder and drop off during remission. Furthermore, it has been shown in clinical trials that anti-inflammatory medicines taken in addition to antidepressants not only significantly improves symptoms but also increases the proportion of subjects positively responding to treatment. Inflammations that lead to serious depression could be caused by common infections such as those caused by a virus, bacteria or even parasites. Researchers have begun to conceptualize ways in which the historical legacies of racism and colonialism may create depressive conditions. Measures of depression include, but are not limited to: Beck Depression Inventory-11 and the 9-item depression scale in the Patient Health Questionnaire (PHQ-9). Both of these measures are psychological tests that ask personal questions of the participant, and have mostly been used to measure the severity of depression. The Beck Depression Inventory is a self-report scale that helps a therapist identify the patterns of depression symptoms and monitor recovery. The responses on this scale can be discussed in therapy to devise interventions for the most distressing symptoms of depression. Depression is the leading cause of disability worldwide, the United Nations (UN) health agency reported, estimating that it affects more than 300 million people worldwide – the majority of them women, young people and the elderly. An estimated 4.4 percent of the global population has depression, according to a report released by the UN World Health Organization (WHO), which shows an 18 percent increase in the number of people living with depression between 2005 and 2015. Depression is a major mental-health cause of disease burden. Its consequences further lead to significant burden in public health, including a higher risk of dementia, premature mortality arising from physical disorders, and maternal depression impacts on child growth and development. Approximately 76% to 85% of depressed people in low- and middle-income countries do not receive treatment; barriers to treatment include: inaccurate assessment, lack of trained health-care providers, social stigma and lack of resources. The stigma comes from misguided societal views that people with mental illness are different from everyone else, and they can choose to get better only if they wanted to. Due to this more than half of the people with depression do not receive help with their disorders. The stigma leads to a strong preference for privacy. An analysis of 40,350 undergraduates from 70 institutions by Posselt and Lipson found that undergraduates who perceived their classroom environments as highly competitive had a 37% higher chance of developing depression and a 69% higher chance of developing anxiety. Several studies have suggested that unemployment roughly doubles the risk of developing depression. The World Health Organization has constructed guidelines – known as The Mental Health Gap Action Programme (mhGAP) – aiming to increase services for people with mental, neurological and substance-use disorders. Depression is listed as one of conditions prioritized by the programme. Trials conducted show possibilities for the implementation of the programme in low-resource primary-care settings dependent on primary-care practitioners and lay health-workers. Examples of mhGAP-endorsed therapies targeting depression include Group Interpersonal Therapy as group treatment for depression and "Thinking Health", which utilizes cognitive behavioral therapy to tackle perinatal depression. Furthermore, effective screening in primary care is crucial for the access of treatments. The mhGAP adopted its approach of improving detection rates of depression by training general practitioners. However, there is still weak evidence supporting this training. According to 2011 study, people who are high in hypercompetitive traits are also likely to measure higher for depression and anxiety. As of 2021, Iranians were one of the most depressed peoples on Earth, with the government reporting a 70% depression rate. The term depression was derived from the Latin verb deprimere, "to press down". From the 14th century, "to depress" meant to subjugate or to bring down in spirits. It was used in 1665 in English author Richard Baker's Chronicle to refer to someone having "a great depression of spirit", and by English author Samuel Johnson in a similar sense in 1753. In Ancient Greece, disease was thought due to an imbalance in the four basic bodily fluids, or humors. Personality types were similarly thought to be determined by the dominant humor in a particular person. Derived from the Ancient Greek melas, "black", and kholé, "bile", melancholia was described as a distinct disease with particular mental and physical symptoms by Hippocrates in his Aphorisms, where he characterized all "fears and despondencies, if they last a long time" as being symptomatic of the ailment. During the 18th century, the humoral theory of melancholia was increasingly being challenged by mechanical and electrical explanations; references to dark and gloomy states gave way to ideas of slowed circulation and depleted energy. German physician Johann Christian Heinroth, however, argued melancholia was a disturbance of the soul due to moral conflict within the patient. In the 20th century, the German psychiatrist Emil Kraepelin distinguished manic depression. The influential system put forward by Kraepelin unified nearly all types of mood disorder into manic–depressive insanity. Kraepelin worked from an assumption of underlying brain pathology, but also promoted a distinction between endogenous (internally caused) and exogenous (externally caused) types. Other psycho-dynamic theories were proposed. Existential and humanistic theories represented a forceful affirmation of individualism. Austrian existential psychiatrist Viktor Frankl connected depression to feelings of futility and meaninglessness. Frankl's logotherapy addressed the filling of an "existential vacuum" associated with such feelings, and may be particularly useful for depressed adolescents. Researchers theorized that depression was caused by a chemical imbalance in neurotransmitters in the brain, a theory based on observations made in the 1950s of the effects of reserpine and isoniazid in altering monoamine neurotransmitter levels and affecting depressive symptoms. During the 1960s and 70s, manic-depression came to refer to just one type of mood disorder (now most commonly known as bipolar disorder) which was distinguished from (unipolar) depression. The terms unipolar and bipolar had been coined by German psychiatrist Karl Kleist. In July 2022, British psychiatrist Joanna Moncrieff, also psychiatrist Mark Horowtiz and others proposed in a study on academic journal Molecular Psychiatry that depression is not caused by a serotonin imbalance in the human body, unlike what most of the psychiatry community points to, and that therefore anti-depressants do not work against the illness. However, such study was met with criticism from some psychiatrists, who argued the study's methodology used an indirect trace of serotonin, instead of taking direct measurements of the molecule. Moncrieff said that, despite her study's conclusions, no one should interrupt their treatment if they are taking any anti-depressant.
