|Lithograph of a man diagnosed as suffering from melancholia with strong suicidal tendency (1892)|
Depression is a state of low mood and aversion to activity. It can affect a person's thoughts, behavior, motivation, feelings, and sense of well-being.  The core symptom of depression is said to be anhedonia, which refers to loss of interest or a loss of feeling of pleasure in certain activities that usually bring joy to people. Depressed mood is a symptom of some mood disorders such as major depressive disorder or 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, hopelessness and, sometimes, suicidal thoughts. It can either be short term or long term.
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. Childhood physical or sexual abuse in particular significantly correlates with the likelihood of experiencing depression over the victim's lifetime.
Life events and changes that may influence depressed moods include (but are not limited to): childbirth, menopause, financial difficulties, unemployment, stress (such as from work, education, family, living conditions etc.), a medical diagnosis (cancer, HIV, etc.), bullying, loss of a loved one, natural disasters, social isolation, rape, relationship troubles, jealousy, separation, or catastrophic injury.Adolescents may be especially prone to experiencing a depressed mood following social rejection, peer pressure, or bullying.
Globally, more than 264 million people of all ages suffer from depression. The global pandemic of COVID-19 has negatively impacted upon individuals mental health, causing levels of depression to surge, reaching devastating heights. A study conducted by the University of Surrey in Autumn 2019 and May/June 2020 looked into the impact of COVID-19 upon young peoples mental health. This study is published in the Journal of Psychiatry Research Report. The study showed a significant rise in depression symptoms and a reduction in overall wellbeing during lockdown (May/June 2020) compared to the previous Autumn (2019). Levels of clinical depression in those surveyed in the study were found to have more than doubled, rising from 14.9 per cent in Autumn 2019 to 34.7 per cent in May/June 2020. This study further emphasises the correlation that certain life events have with developing depression.
Changes in personality or in one's social environment can affect levels of depression. High scores on the personality domain neuroticism make the development of depressive symptoms as well as all kinds of depression diagnoses more likely, and depression is associated with low extraversion. Other personality indicators could be: temporary but rapid mood changes, short term hopelessness, loss of interest in activities that used to be of a part of one's life, sleep disruption, withdrawal from previous social life, appetite changes, and difficulty concentrating.
Alcohol can be a depressant which slows down some regions of the brain, like the prefrontal and temporal cortex, negatively affecting rationality and memory. It also lowers the level of serotonin in the brain, which could potentially lead to higher chances of depressive mood.
The connection between the amount of alcohol intake, level of depressed mood, and how it affects the risks of experiencing consequences from alcoholism, were studied in a research done on college students. The study used 4 latent, distinct profiles of different alcohol intake and level of depression; Mild or Moderate Depression, and Heavy or Severe Drinkers. Other indicators consisting of social factors and individual behaviors were also taken into consideration in the research. Results showed that the level of depression as an emotion negatively affected the amount of risky behavior and consequence from drinking, while having an inverse relationship with protective behavioral strategies, which are behavioral actions taken by oneself for protection from the relative harm of alcohol intake. Having an elevated level of depressed mood does therefore lead to greater consequences from drinking.
Social abuse, such as bullying, are defined as actions of singling out and causing harm on vulnerable individuals. In order to capture a day-to-day observation of the relationship between the damaging effects of social abuse, the victim's mental health and depressive mood, a study was conducted on whether individuals would have a higher level of depressed mood when exposed to daily acts of negative behavior. The result concluded that being exposed daily to abusive behaviors such as bullying has a positive relationship to depressed mood on the same day.
The study has also gone beyond to compare the level of depressive mood between the victims and non-victims of the daily bullying. Although victims were predicted to have a higher level of depressive mood, the results have shown otherwise that exposure to negative acts has led to similar levels of depressive mood, regardless of the victim status. The results therefore have concluded that bystanders and non-victims feel as equally depressed as the victim when being exposed to acts such as social abuse.
Depression may also be the result of healthcare, such as with medication induced depression. Therapies associated with depression include interferon therapy, beta-blockers, isotretinoin, contraceptives, cardiac agents, anticonvulsants, antimigraine drugs, antipsychotics, and hormonal agents such as gonadotropin-releasing hormone agonist.
Several drugs of abuse can cause or exacerbate depression, whether in intoxication, withdrawal, and from chronic use. These include alcohol, sedatives (including prescription benzodiazepines), opioids (including prescription pain killers and illicit drugs such as heroin), stimulants (such as cocaine and amphetamines), hallucinogens, and inhalants.
Depressed mood can be the result of a number of infectious diseases, nutritional deficiencies, neurological conditions, and physiological problems, including hypoandrogenism (in men), Addison's disease, Cushing's syndrome, hypothyroidism, hyperparathyroidism, Lyme disease, multiple sclerosis, Parkinson's disease, chronic pain, stroke,diabetes, and cancer.
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 (MDD; 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 mood disturbance appearing as 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;:355 and posttraumatic stress disorder, a mental disorder that sometimes follows trauma, is commonly accompanied by depressed mood.
Measures of depression as an emotional disorder include, but are not limited to: Beck Depression Inventory-11 and the 9-item depression scale in the Patient Health Questionnaire. 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 (BDI) 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. Several studies, however, have used these measures to also determine healthy individuals who are not suffering from depression as a mental disorder, but as an occasional mood disorder. This is substantiated by the fact that depression as an emotional disorder displays similar symptoms to minimal depression and low levels of mental disorders such as major depressive disorder; therefore, researchers were able to use the same measure interchangeably. In terms of the scale, participants scoring between 0-13 and 0-4 respectively were considered healthy individuals.
Another measure of depressed mood would be the IWP Multi-affect Indicator. It is a psychological test that indicates various emotions, such as enthusiasm and depression, and asks for the degree of the emotions that the participants have felt in the past week. There are studies that have used lesser items from the IWP Multi-affect Indicator which was then scaled down to daily levels to measure the daily levels of depression as an emotional disorder.
Divergent thinking is defined as a thought process that generates creativity in ideas by exploring many possible solutions. Having a depressed mood will significantly reduce the possibility of divergent thinking, as it reduces the fluency, variety and the extent of originality of the possible ideas generated.
However, some depressive mood disorders might have a positive effect for creativity. Upon identifying several studies and analyzing data involving individuals with high levels of creativity, Christa Taylor was able to conclude that there is a clear positive relationship between creativity and depressive mood. A possible reason is that having a low mood could lead to new ways of perceiving and learning from the world, but it is unable to account for certain depressive disorders. The direct relationship between creativity and depression remains unclear, but the research conducted on this correlation has shed light that individuals who are struggling with a depressive disorder may be having even higher levels of creativity than a control group, and would be a close topic to monitor depending on the future trends of how creativity will be perceived and demanded.
Schools of depression theories include:
Depressed mood may not require professional treatment, and may be a normal temporary reaction to life events, a symptom of some medical condition, or a side effect of some drugs or medical treatments. A prolonged depressed mood, especially in combination with other symptoms, may lead to a diagnosis of a psychiatric or medical condition which may benefit from treatment. The UK National Institute for Health and Care Excellence (NICE) 2009 guidelines indicate that antidepressants should not be routinely used for the initial treatment of mild depression, because the risk-benefit ratio is poor. Physical activity can have a protective effect against the emergence of depression.
Physical activity can also decrease depressive symptoms due to the release of neurotrophic proteins in the brain that can help to rebuild the hippocampus that may be reduced due to depression. Also yoga could be considered an ancillary treatment option for patients with depressive disorders and individuals with elevated levels of depression.
Reminiscence of old and fond memories is another alternative form of treatment, especially for the elderly who have lived longer and have more experiences in life. It is a method that causes a person to recollect memories of their own life, leading to a process of self-recognition and identifying familiar stimuli. By maintaining one's personal past and identity, it is a technique that stimulates people to view their lives in a more objective and balanced way, causing them to pay attention to positive information in their life stories, which would successfully reduce depressive mood levels.
Self-help books are a growing form of treatment for peoples physiological distress. There may be a possible connection between consumers of unguided self-help books and higher levels of stress and depressive symptoms. Researchers took many factors into consideration to find a difference in consumers and nonconsumers of self-help books. The study recruited 32 people between the ages of 18 and 65; 18 consumers and 14 nonconsumers, in both groups 75% of them were female. Then they broke the consumers into 11 who preferred problem-focused and 7 preferred growth-oriented. Those groups were tested for many things including cortisol levels, depressive symptomatology, and stress reactivity levels. There were no large differences between consumers of self-help books and nonconsumers when it comes to diurnal cortisol level, there was a large difference in depressive symptomatology with consumers having a higher mean score. The growth-oriented group has higher stress reactivity levels than the problem-focused group. However, the problem-focused group shows higher depressive symptomatology.
There are empirical evidences of a connection between the type of stress management techniques and the level of daily depressive mood.
Problem-focused coping leads to lower level of depression. Focusing on the problem allows for the subjects to view the situation in an objective way, evaluating the severity of the threat in an unbiased way, thus it lowers the probability of having depressive responses. On the other hand, emotion-focused coping promotes a depressed mood in stressful situations. The person has been contaminated with too much irrelevant information and loses focus on the options for resolving the problem. They fail to consider the potential consequences and choose the option that minimizes stress and maximizes well-being.
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 suffers from 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 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 programme adopted its approach of improving detection rates of depression by training general practitioners. However, there is still weak evidence supporting this training.
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The Greco-Roman world used the tradition of the four humours to attempt to systematise sadness as "melancholia". This concept remained an important part of European and Islamic medicine until falling out of scientific favour in the 19th century.Emil Kraepelin gave a noted scientific account of depression (German: das manisch-depressive Irresein) in his 1896 psychology encyclopedia "Psychiatrie".
Le mot mélancholie, consacré dans la langue vulgaire, pour exprimer l'état habituel de tristesse de quelques individus, doit etre laissé aux moralistes et aux poètes [...].Missing or empty
|title=(help) quoted in: Peeters, Harry F. M. (2006) . "The historical vicissitudes of mental diseases: Their character and treatment". In Graumann, Carl F.; Gergen, Kenneth J. (eds.). Historical Dimensions of Psychological Discourse. Cambridge: Cambridge University Press. p. 217. ISBN 9780521034760. Retrieved 2021.
Depression as a distinct mental disease was formulated as such for the first time by Kraepelin [...] in the 5th edition (1896) of his Psychiatrie. Ein Lehrbuch für Studi[e]rende und Aertze.