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Depression is a mental state of low mood and aversion to activity, which affects more than 280 million people of all ages (about 3.5% of the global population). Classified medically as a mental and behavioral disorder, the experience of depression affects 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 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, hopelessness and suicidal thoughts. It can either be short term or long term.


Factors


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. Childhood physical or sexual abuse in particular significantly correlates with the likelihood of experiencing depression over the survivor'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. The global pandemic of
COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was identified in Wuhan, China, in December 2019. The disease quick ...
has negatively impacted upon many 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 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was identified in Wuhan, China, in December 2019. The disease quick ...
upon young people's mental health. This study is published in the ''Journal of Psychiatry Research Report''. The study showed a significant rise in
depression symptoms Major depressive disorder (MDD), also known as clinical depression, is a mental disorder characterized by at least two weeks of pervasive low mood, low self-esteem, and loss of interest or pleasure in normally enjoyable activities. Introd ...
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.


Personality

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.


Alcoholism

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.


Bullying

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 survivor's
mental health Mental health encompasses emotional, psychological, and social well-being, influencing cognition, perception, and behavior. It likewise determines how an individual handles Stress (biology), stress, interpersonal relationships, and decision-maki ...
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.


Medical treatments

Depression may also be the result of healthcare, such as with medication induced depression. Therapies associated with depression include interferon therapy,
beta-blockers Beta blockers, also spelled β-blockers, are a class of medications that are predominantly used to manage abnormal heart rhythms, and to protect the heart from a second heart attack after a first heart attack (secondary prevention). They are al ...
, isotretinoin, contraceptives, anticonvulsants,
antimigraine drug Antimigraine drugs are medications intended to reduce the effects or intensity of migraine headache. They include drugs for the treatment of acute migraine symptoms as well as drugs for the prevention of migraine attacks. Treatment of acute symp ...
s, antipsychotics, hormonal agents such as gonadotropin-releasing hormone agonist, magnetic stimulation to brain and electric therapy.


Substance-induced

Several drugs of abuse can cause or exacerbate depression, whether in
intoxication Intoxication — or poisoning, especially by an alcoholic or narcotic substance — may refer to: * Substance intoxication: ** Alcohol intoxication ** LSD intoxication ** Toxidrome ** Tobacco intoxication ** Cannabis intoxication ** Cocaine in ...
, 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 Substituted amphetamines are a class of compounds based upon the amphetamine structure; it includes all derivative compounds which are formed by replacing, or substituting, one or more hydrogen atoms in the amphetamine core structure with sub ...
), hallucinogens, and
inhalants Inhalants are a broad range of household and industrial chemicals whose volatile vapors or pressurized gases can be concentrated and breathed in via the nose or mouth to produce intoxication, in a manner not intended by the manufacturer. They ...
.


Non-psychiatric illnesses

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 Addison's disease, also known as primary adrenal insufficiency, is a rare long-term endocrine disorder characterized by inadequate production of the steroid hormones cortisol and aldosterone by the two outer layers of the cells of the adrena ...
, cushing's syndrome, pernicious anemia, hypothyroidism,
hyperparathyroidism Hyperparathyroidism is an increase in parathyroid hormone (PTH) levels in the blood. This occurs from a disorder either within the parathyroid glands (primary hyperparathyroidism) or as response to external stimuli (secondary hyperparathyroidism) ...
,
Lyme disease Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the '' Borrelia'' bacterium, which is spread by ticks in the genus '' Ixodes''. The most common sign of infection is an expanding red rash, known as erythema ...
, multiple sclerosis,
Parkinson's disease Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms beco ...
, chronic pain, stroke, diabetes, and cancer.


Psychiatric syndromes

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 Bipolar disorder, previously known as manic depression, is a mental disorder characterized by periods of Depression (mood), depression and periods of abnormally elevated Mood (psychology), mood that last from days to weeks each. If the elevat ...
, 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 Adjustment disorder is a maladaptive response to a psychosocial stressor. It is classified as a mental disorder. The maladaptive response usually involves otherwise normal emotional and behavioral reactions that manifest more intensely than usual ...
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; and
posttraumatic stress disorder Post-traumatic stress disorder (PTSD) is a mental and behavioral disorder that can develop because of exposure to a traumatic event, such as sexual assault, warfare, traffic collisions, child abuse, domestic violence, or other threat ...
, a mental disorder that sometimes follows
trauma Trauma most often refers to: *Major trauma, in physical medicine, severe physical injury caused by an external source *Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic inju ...
, is commonly accompanied by depressed mood.


Historical legacy

Researchers have begun to conceptualize ways in which the historical legacies of
racism Racism is the belief that groups of humans possess different behavioral traits corresponding to inherited attributes and can be divided based on the superiority of one race over another. It may also mean prejudice, discrimination, or antagoni ...
and colonialism may create depressive conditions.


Measures

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 (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 (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 experincing 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.


Creative thinking

Divergent thinking Divergent thinking is a thought process or method used to generate creative ideas by exploring many possible solutions. It typically occurs in a spontaneous, free-flowing, "non-linear" manner, such that many ideas are generated in an emergent co ...
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. 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.


Theories

Schools of depression theories include: * Cognitive theory of depression * Tripartite Model of Anxiety and Depression *
Behavioral theories of depression Behavioral theories of depression explain the etiology of depression based on the behavioural sciences, and they form the basis for behavioral therapies for depression. Behavioral theories Introduction Depression is a significant mental illness ...
*
Evolutionary approaches to depression Evolutionary approaches to depression are attempts by evolutionary psychologists to use the theory of evolution to shed light on the problem of mood disorders within the perspective of evolutionary psychiatry. Depression is generally thought of a ...
* Biology of depression * Epigenetics of depression


Management

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 Reminiscence is the act of recollecting past experiences or events. An example of the typical use of reminiscence is when people share their personal stories with others or allows other people to live vicariously through stories of family, frien ...
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 (signs and symptoms) 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 is limited evidence that continuing antidepressant medication for one year reduces the risk of depression recurrence with no additional harm. Recommendations for psychological treatments or combination treatments in preventing recurrence are not clear. There are empirical evidences of a connection between the type of stress management techniques and the level of daily depressive mood.


Epidemiology

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 Disease burden is the impact of a health problem as measured by financial cost, mortality, morbidity, or other indicators. It is often quantified in terms of quality-adjusted life years (QALYs) or disability-adjusted life years (DALYs). Both ...
. 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. The
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level o ...
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.


History

The term ''depression'' was derived from the
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
verb , "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 , "black", and , "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 In a variety of contexts, exogeny or exogeneity () is the fact of an action or object originating externally. It contrasts with endogeneity or endogeny, the fact of being influenced within a system. Economics In an economic model, an exogen ...
(externally caused) types. Around 1980, Kraepelin defined the term manic depression, which is also known as bipolar disorder. This mental health condition causes people to have mood swings, such as emotional highs and lows. Manic depression and bipolar disorder are considered the same thing because of these mood swings. 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 Logotherapy was developed by neurologist and psychiatrist Viktor Frankl and is based on the premise that the primary motivational force of an individual is to find a meaning in life. Frankl describes it as "the Third Viennese School of Psych ...
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 Reserpine is a drug that is used for the treatment of high blood pressure, usually in combination with a thiazide diuretic or vasodilator. Large clinical trials have shown that combined treatment with reserpine plus a thiazide diuretic reduces ...
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 Bipolar disorder, previously known as manic depression, is a mental disorder characterized by periods of Depression (mood), depression and periods of abnormally elevated Mood (psychology), mood that last from days to weeks each. If the elevat ...
) which was distinguished from (unipolar) depression. The terms unipolar and bipolar had been coined by German psychiatrist
Karl Kleist Karl Kleist (born 31 January 1879 in Mulhouse, Alsace, died 26 December 1960) was a German neurologist and psychiatrist who made notable advances in descriptive psychopathology and neuropsychology. Kleist coined the terms unipolar (‘einpolig’) ...
. In July 2022, British psychiatrist Joanna Moncrieff, also psychiatrist Mark Horowtiz and others proposed in a study on academic journal
Molecular Psychiatry ''Molecular Psychiatry'' is a peer-reviewed scientific journal published by Nature Publishing Group. It covers research in biological psychiatry. Abstracting and indexing The journal is abstracted and indexed in: According to the '' Journal Ci ...
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 don't 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.


See also


References


External links

* {{Authority control Emotions Neuropsychology Mental states