Evolutionary approaches to depression
Encyclopedia
Evolutionary psychology
has proposed several different evolutionary explanations for depression
.
); it is also an important risk factor for suicide. It is understandable, then, that clinical depression is thought to be a pathology — a major dysfunction of the brain.
In most cases, rates of organ dysfunction increase with age, with low rates in adolescents and young adults, and the highest rates in the elderly. These patterns are consistent with evolutionary theories of aging
which posit that selection against dysfunctional traits decreases with age (because there is a decreasing probability of surviving to later ages).
In contrast to these patterns, prevalence of clinical depression is high in all age categories, including otherwise healthy adolescents and young adults. In one study of the US population, for example, the 12 month prevalence for a major depression episode was highest in the youngest age category (15–24 year olds). The high prevalence of depression is also an outlier when compared to the prevalence of major mental retardation
, autism
, and schizophrenia
, all with prevalence rates about one tenth that of depression, or less.
The common occurrence and persistence of a trait
like clinical depression with such negative effects early in life is difficult to explain. (Rates of infectious disease are high in young people, of course, but clinical depression is not thought to be caused by an infection.) Evolutionary psychology
and its application in evolutionary medicine
suggest how behaviour and mental states, including seemingly harmful states such as depression, may be past adaptations to recurring reproductive problems faced by our ancestors, actually having improved (however disadvantageous in the modern world), the fitness
of either the individual or their relatives
. It has been argued, for example, that Abraham Lincoln's
life-long depression was a source of insight and strength. Some even suggest that "we aren’t designed to have happiness as our natural default" and so a state of depression is the evolutionary norm.
The following hypotheses
attempt to identify a benefit of depression that outweighs its obvious costs.
Such hypotheses are not necessarily incompatible with one another and may explain different aspects, causes, and symptoms of depression.
is also very distressful, yet it has an evolved function: to inform the organism that it is suffering damage, to motivate it to withdraw from the source of damage, and to learn to avoid such damage-causing circumstances in the future.
According to the psychic pain hypothesis, depression is analogous to physical pain in that it informs the sufferer that current circumstances, such as the loss of a friend, are imposing a threat to biological fitness
, it motivates the sufferer to cease activities that led to the costly situation, if possible, and it causes him or her to learn to avoid similar circumstances in the future. Proponents of this view tend to focus on low mood, and regard clinical depression as a dysfunctional extreme of low mood.
and lack of energy, and those experiencing it are risk-aversive and perceive more negative and pessimistic outcomes because they are focused on preventing further loss. Although the model views depression as an adaptive response, it does not suggest that it is beneficial by the standards of current society; but it does suggest that many approaches to depression treat symptoms rather than causes, and underlying social problems need to be addressed.
One way depression increases the individual’s focus on a problem is by inducing rumination. Depression activates the left ventrolateral prefrontal cortex, which increases attention control and maintains problem-related information in an “active, accessible state” referred to as “working memory,” or WM. As a result, depressed individuals have been shown to ruminate, reflecting on the reasons for their current problems. Feelings of regret associated with depression also cause individuals to reflect and analyze past events in order to determine why they happened and how they could have been prevented.
Another way depression increases an individual’s ability to concentrate on a problem is by reducing distraction from the problem. For example, anhedonia, which is often associated with depression, decreases an individual’s desire to participate in activities that provide short-term rewards, and instead, allows the individual to concentrate on long-term goals. In addition, “psychomotory changes,” such as solitariness, decreased appetite, and insomnia also reduce distractions. For instance, insomnia enables conscious analysis of the problem to be maintained by preventing sleep from disrupting such processes. Likewise, solitariness, lack of physical activity, and lack of appetite all eliminate sources of distraction, such as social interactions, navigation through the environment, and “oral activity,” which disrupt stimuli from being processed.
Thus, unlike other evolutionary theories this one sees depression as an maladaptive extreme of something that is beneficial in smaller amounts. In particular, one theory focuses on the personality trait neuroticism
. Low amounts of neuroticism may increase a person fitness through various process but too much may reduce fitness by for example recurring depressions. Thus, evolution will select for an optimal amount and most people will have neuroticism near this amount. However, genetic variation continually occurs and some people will have high neuroticism which increases the risk of depressions.
is the hypothesis that, if an individual is involved in a lengthy fight for dominance
in a social group and is clearly losing, then depression causes the individual to back down and accept the submissive
role. In doing so, the individual is protected from unnecessary harm. In this way, depression helps maintain a social hierarchy. This theory is a special case of a more general theory derived from the psychic pain hypothesis: that the cognitive response that produces modern-day depression evolved as a mechanism that allows people to assess whether they are in pursuit of an unreachable goal
, and if they are, to motivate them to desist.
Depression, resulting from one’s loss of what one approach calls "Social Attention Holding Power," or SAHP, may have signalled the individual's submissiveness to the more dominant males of the social group through associated symptoms, such as low confidence and anxiety. This, in turn, reduced tension among group members, and enabled bonds to be maintained. Secondly, depression may also have served to signal other members of an individual’s need for aid and desire to reform lost bonds.
. In the wake of a serious negative life event, such as those that have been implicated in depression (e.g., death, divorce), "cheap" signals of need, such as crying, might not be believed when social partners have conflicts of interest. The symptoms of major depression, such as loss of interest in virtually all activities and suicidality
, are inherently costly, but, as costly signaling theory requires, the costs differ for individuals in different states. For individuals who are not genuinely in need, the fitness
cost of major depression is very high because it threatens the flow of fitness benefits. For individuals who are in genuine need, however, the fitness cost of major depression is low, because the individual is not generating many fitness benefits. Thus, only an individual in genuine need can afford to suffer major depression. Major depression therefore serves as an honest, or credible, signal of need.
For example, individuals suffering a severe loss such as the death of a spouse
are often in need of help and assistance from others. Such individuals who have few conflicts with their social partners are predicted to experience grief—a means, in part, to signal need to others. Such individuals who have many conflicts with their social partners, in contrast, are predicted to experience depression—a means, in part, to credibly signal need to others who might be skeptical that the need is genuine.
The bargaining theory of depression is similar to the honest signaling, niche change, and social navigation theories of depression described above. It draws on theories of labor strikes developed by economists to basically add one additional element to honest signaling theory: The fitness of social partners is generally correlated. When a wife suffers depression and reduces her investment in offspring, for example, the husband's fitness is also put at risk. Thus, not only do the symptoms of major depression serve as costly and therefore honest signals of need, they also compel reluctant social partners to respond to that need in order to prevent their own fitness from being reduced.
and psychomotor retardation
or agitation, provides a focused sober perspective on socially imposed constraints hindering a person’s pursuit of major fitness enhancing projects. Simultaneously, publicly displayed symptoms, which reduce the depressive's ability to conduct basic life activities, serve as a social signal
of need; the signal's costliness for the depressive certifies its honesty. Finally, for social partners who find it uneconomical to respond helpfully to an honest signal of need, the same depressive symptoms also have the potential to extort relevant concessions and compromises. Depression’s extortionary power comes from the fact that it retards the flow of just those goods and services such partners have come to expect from the depressive under status quo socioeconomic arrangements.
Thus depression may be a social adaptation
especially useful in motivating a variety of social partners, all at once, to help the depressive initiate major fitness-enhancing changes in their socioeconomic life. There are diverse circumstances under which this may become necessary in human social life, ranging from loss of rank or a key social ally which makes the current social niche uneconomic to having a set of creative new ideas about how to make a livelihood which begs for a new niche. The social navigation hypothesis emphasizes that an individual can become tightly ensnared in an overly restrictive matrix of social exchange contracts, and that this situation sometimes necessitates a radical contractual upheaval that is beyond conventional methods of negotiation. Regarding the treatment of depression, this hypothesis calls into question any assumptions by the clinician that the typical cause of depression is related to maladaptive
perverted thinking processes or other purely endogenous sources. The social navigation hypothesis calls instead for analysis of the depressive’s talents and dreams, identification of relevant social constraints (especially those with a relatively diffuse non-point source within the social network of the depressive), and practical social problem-solving
therapy
designed to relax those constraints enough to allow the depressive to move forward with their life under an improved set of social contracts. This theory has been the subject of criticism..
in both the affected individual and his/her kin.
First, the associated symptoms of depression, such as inactivity and lethargy, encourage the affected individual to rest. Energy conserved through such methods is highly crucial, as immune activation against infections is relatively costly; there must be, for instance, a 10% increase in metabolic activity for even a 1℃ change in body temperature. Therefore, depression allows one to conserve and allocate energy to the immune system more efficiently.
Depression further prevents infection by discouraging social interactions and activities that may result in exchange of infections. For example, the loss of interest discourages one from engaging in sexual activity, which, in turn, prevents the exchange of sexually transmitted diseases. Similarly, depressed mothers may interact less with their children, reducing the probability of the mother infecting her kin.
Lastly, the lack of appetite associated with depression may also reduce exposure to food-borne parasites.
Evolutionary psychology
Evolutionary psychology is an approach in the social and natural sciences that examines psychological traits such as memory, perception, and language from a modern evolutionary perspective. It seeks to identify which human psychological traits are evolved adaptations, that is, the functional...
has proposed several different evolutionary explanations for depression
Mood disorder
Mood disorder is the term designating a group of diagnoses in the Diagnostic and Statistical Manual of Mental Disorders classification system where a disturbance in the person's mood is hypothesized to be the main underlying feature...
.
Background
Major depression is a leading cause of disability worldwide, and in 2000 was the fourth leading contributor to the global burden of disease (measured in DALYsDisability-adjusted life years
The disability-adjusted life year is a measure of overall disease burden, expressed as the number of years lost due to ill-health, disability or early death. Originally developed by Harvard University for the World Bank in 1990, the World Health Organization subsequently adopted the method in 2000...
); it is also an important risk factor for suicide. It is understandable, then, that clinical depression is thought to be a pathology — a major dysfunction of the brain.
In most cases, rates of organ dysfunction increase with age, with low rates in adolescents and young adults, and the highest rates in the elderly. These patterns are consistent with evolutionary theories of aging
Senescence
Senescence or biological aging is the change in the biology of an organism as it ages after its maturity. Such changes range from those affecting its cells and their function to those affecting the whole organism...
which posit that selection against dysfunctional traits decreases with age (because there is a decreasing probability of surviving to later ages).
In contrast to these patterns, prevalence of clinical depression is high in all age categories, including otherwise healthy adolescents and young adults. In one study of the US population, for example, the 12 month prevalence for a major depression episode was highest in the youngest age category (15–24 year olds). The high prevalence of depression is also an outlier when compared to the prevalence of major mental retardation
Mental retardation
Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...
, autism
Autism
Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...
, and schizophrenia
Schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
, all with prevalence rates about one tenth that of depression, or less.
The common occurrence and persistence of a trait
Trait (biology)
A trait is a distinct variant of a phenotypic character of an organism that may be inherited, environmentally determined or be a combination of the two...
like clinical depression with such negative effects early in life is difficult to explain. (Rates of infectious disease are high in young people, of course, but clinical depression is not thought to be caused by an infection.) Evolutionary psychology
Evolutionary psychology
Evolutionary psychology is an approach in the social and natural sciences that examines psychological traits such as memory, perception, and language from a modern evolutionary perspective. It seeks to identify which human psychological traits are evolved adaptations, that is, the functional...
and its application in evolutionary medicine
Evolutionary medicine
Evolutionary medicine or Darwinian medicine is the application of modern evolutionary theory to understanding health and disease. It provides a complementary scientific approach to the present mechanistic explanations that dominate medical science, and particularly modern medical education...
suggest how behaviour and mental states, including seemingly harmful states such as depression, may be past adaptations to recurring reproductive problems faced by our ancestors, actually having improved (however disadvantageous in the modern world), the fitness
Fitness (biology)
Fitness is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype in a given environment...
of either the individual or their relatives
Kin selection
Kin selection refers to apparent strategies in evolution that favor the reproductive success of an organism's relatives, even at a cost to the organism's own survival and reproduction. Charles Darwin was the first to discuss the concept of group/kin selection...
. It has been argued, for example, that Abraham Lincoln's
Abraham Lincoln
Abraham Lincoln was the 16th President of the United States, serving from March 1861 until his assassination in April 1865. He successfully led his country through a great constitutional, military and moral crisis – the American Civil War – preserving the Union, while ending slavery, and...
life-long depression was a source of insight and strength. Some even suggest that "we aren’t designed to have happiness as our natural default" and so a state of depression is the evolutionary norm.
The following hypotheses
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...
attempt to identify a benefit of depression that outweighs its obvious costs.
Such hypotheses are not necessarily incompatible with one another and may explain different aspects, causes, and symptoms of depression.
Psychic pain hypothesis
One reason depression is thought to be a pathology is that it causes so much psychic pain and distress. However, physical painPain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
is also very distressful, yet it has an evolved function: to inform the organism that it is suffering damage, to motivate it to withdraw from the source of damage, and to learn to avoid such damage-causing circumstances in the future.
According to the psychic pain hypothesis, depression is analogous to physical pain in that it informs the sufferer that current circumstances, such as the loss of a friend, are imposing a threat to biological fitness
Fitness (biology)
Fitness is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype in a given environment...
, it motivates the sufferer to cease activities that led to the costly situation, if possible, and it causes him or her to learn to avoid similar circumstances in the future. Proponents of this view tend to focus on low mood, and regard clinical depression as a dysfunctional extreme of low mood.
Behavioral shutdown model
A similar theory to the psychic pain hypothesis. If an organism faces more risk or expenditure than reward from activities, the best evolutionary strategy may be to withdraw from them. The behavioral shutdown model proposes that emotional pain, like physical pain, serves a useful adaptive purpose. Negative emotions like disappointment, sadness, grief, fear, anxiety, anger, and guilt are described as "evolved strategies that allow for the identification and avoidance of specific problems, especially in the social domain." Depression is characteristically associated with anhedoniaAnhedonia
In psychology and psychiatry, anhedonia is defined as the inability to experience pleasure from activities usually found enjoyable, e.g. hobbies, exercise, social interaction or sexual activity....
and lack of energy, and those experiencing it are risk-aversive and perceive more negative and pessimistic outcomes because they are focused on preventing further loss. Although the model views depression as an adaptive response, it does not suggest that it is beneficial by the standards of current society; but it does suggest that many approaches to depression treat symptoms rather than causes, and underlying social problems need to be addressed.
Analytical rumination hypothesis
This hypothesis suggests that depression is an adaptation that causes the affected individual to concentrate his or her attention and focus on a complex problem in order to analyze and solve it.One way depression increases the individual’s focus on a problem is by inducing rumination. Depression activates the left ventrolateral prefrontal cortex, which increases attention control and maintains problem-related information in an “active, accessible state” referred to as “working memory,” or WM. As a result, depressed individuals have been shown to ruminate, reflecting on the reasons for their current problems. Feelings of regret associated with depression also cause individuals to reflect and analyze past events in order to determine why they happened and how they could have been prevented.
Another way depression increases an individual’s ability to concentrate on a problem is by reducing distraction from the problem. For example, anhedonia, which is often associated with depression, decreases an individual’s desire to participate in activities that provide short-term rewards, and instead, allows the individual to concentrate on long-term goals. In addition, “psychomotory changes,” such as solitariness, decreased appetite, and insomnia also reduce distractions. For instance, insomnia enables conscious analysis of the problem to be maintained by preventing sleep from disrupting such processes. Likewise, solitariness, lack of physical activity, and lack of appetite all eliminate sources of distraction, such as social interactions, navigation through the environment, and “oral activity,” which disrupt stimuli from being processed.
Possibilities of depression as a dysregulated adaptation
Depression, especially in the modern context, may not necessarily be adaptive. The ability to feel pain and experience depression, are adaptive defense mechanisms, but when they are “too easily triggered, too intense, or long lasting,” they can become “dysregulated.” In such a case, defense mechanisms, too, can become diseases, such as “chronic pain or dehydration from diarrhea.” Depression, which may be a similar kind of defense mechanism, may have become dysregulated as well.Thus, unlike other evolutionary theories this one sees depression as an maladaptive extreme of something that is beneficial in smaller amounts. In particular, one theory focuses on the personality trait neuroticism
Neuroticism
Neuroticism is a fundamental personality trait in the study of psychology. It is an enduring tendency to experience negative emotional states. Individuals who score high on neuroticism are more likely than the average to experience such feelings as anxiety, anger, guilt, and depressed mood...
. Low amounts of neuroticism may increase a person fitness through various process but too much may reduce fitness by for example recurring depressions. Thus, evolution will select for an optimal amount and most people will have neuroticism near this amount. However, genetic variation continually occurs and some people will have high neuroticism which increases the risk of depressions.
Rank theory
Rank theoryRank theory of depression
Rank theory is an evolutionary theory of depression, developed by Anthony Stevens and John Price, and proposes that depression promotes the survival of genes. It is an adaptive response to losing status and losing confidence in the ability to regain it. The adaptive function of the depression is...
is the hypothesis that, if an individual is involved in a lengthy fight for dominance
Dominance
Dominance may refer to:* Dominance , an aspect of virtual inheritance in the C++ programming language* Dominance , in economics, the degree of inequality in market share distribution...
in a social group and is clearly losing, then depression causes the individual to back down and accept the submissive
Submission
Submission is the acknowledgement of the legitimacy of the power of one's superior or superiors.Submission may also refer to:* Submission/Submitter , an Islamic organisation...
role. In doing so, the individual is protected from unnecessary harm. In this way, depression helps maintain a social hierarchy. This theory is a special case of a more general theory derived from the psychic pain hypothesis: that the cognitive response that produces modern-day depression evolved as a mechanism that allows people to assess whether they are in pursuit of an unreachable goal
Goal
A goal is an objective, or a projected computation of affairs, that a person or a system plans or intends to achieve.Goal, GOAL or G.O.A.L may also refer to:Sport...
, and if they are, to motivate them to desist.
Social risk hypothesis
This hypothesis is similar to the rank hypothesis but focuses more on general social approval in a group rather than direct dominance contests. To maintain social ties were critical for survival and reproduction. During the Pleistocene period, for instance, such social ties were vital in food foraging and protection from predators.Depression, resulting from one’s loss of what one approach calls "Social Attention Holding Power," or SAHP, may have signalled the individual's submissiveness to the more dominant males of the social group through associated symptoms, such as low confidence and anxiety. This, in turn, reduced tension among group members, and enabled bonds to be maintained. Secondly, depression may also have served to signal other members of an individual’s need for aid and desire to reform lost bonds.
Honest signaling theory
Another reason depression is thought to be a pathology is that key symptoms, such as loss of interest in virtually all activities, are extremely costly to the sufferer. Biologists and economists have proposed, however, that signals with inherent costs can credibly signal information when there are conflicts of interestConflict of interest
A conflict of interest occurs when an individual or organization is involved in multiple interests, one of which could possibly corrupt the motivation for an act in the other....
. In the wake of a serious negative life event, such as those that have been implicated in depression (e.g., death, divorce), "cheap" signals of need, such as crying, might not be believed when social partners have conflicts of interest. The symptoms of major depression, such as loss of interest in virtually all activities and suicidality
Suicide
Suicide is the act of intentionally causing one's own death. Suicide is often committed out of despair or attributed to some underlying mental disorder, such as depression, bipolar disorder, schizophrenia, alcoholism, or drug abuse...
, are inherently costly, but, as costly signaling theory requires, the costs differ for individuals in different states. For individuals who are not genuinely in need, the fitness
Fitness (biology)
Fitness is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype in a given environment...
cost of major depression is very high because it threatens the flow of fitness benefits. For individuals who are in genuine need, however, the fitness cost of major depression is low, because the individual is not generating many fitness benefits. Thus, only an individual in genuine need can afford to suffer major depression. Major depression therefore serves as an honest, or credible, signal of need.
For example, individuals suffering a severe loss such as the death of a spouse
Marriage
Marriage is a social union or legal contract between people that creates kinship. It is an institution in which interpersonal relationships, usually intimate and sexual, are acknowledged in a variety of ways, depending on the culture or subculture in which it is found...
are often in need of help and assistance from others. Such individuals who have few conflicts with their social partners are predicted to experience grief—a means, in part, to signal need to others. Such individuals who have many conflicts with their social partners, in contrast, are predicted to experience depression—a means, in part, to credibly signal need to others who might be skeptical that the need is genuine.
Bargaining theory
Depression is not only costly to the sufferer, it also imposes a significant burden on family, friends, and society at large—yet another reason it is thought to be pathological. Yet if sufferers of depression have real but unmet needs, they might have to provide an incentive to others to address those needs.The bargaining theory of depression is similar to the honest signaling, niche change, and social navigation theories of depression described above. It draws on theories of labor strikes developed by economists to basically add one additional element to honest signaling theory: The fitness of social partners is generally correlated. When a wife suffers depression and reduces her investment in offspring, for example, the husband's fitness is also put at risk. Thus, not only do the symptoms of major depression serve as costly and therefore honest signals of need, they also compel reluctant social partners to respond to that need in order to prevent their own fitness from being reduced.
Social navigation or niche change theory
The social navigation or niche change hypothesis combines the analytical rumination and bargaining hypotheses and suggests that depression, operationally defined as a combination of prolonged anhedoniaAnhedonia
In psychology and psychiatry, anhedonia is defined as the inability to experience pleasure from activities usually found enjoyable, e.g. hobbies, exercise, social interaction or sexual activity....
and psychomotor retardation
Psychomotor retardation
Psychomotor retardation involves a slowing-down of thought and a reduction of physical movements in an individual. Psychomotor retardation can cause a visible slowing of physical and emotional reactions, including speech and affect...
or agitation, provides a focused sober perspective on socially imposed constraints hindering a person’s pursuit of major fitness enhancing projects. Simultaneously, publicly displayed symptoms, which reduce the depressive's ability to conduct basic life activities, serve as a social signal
Signalling theory
Within evolutionary biology, signalling theory is a body of theoretical work examining communication between individuals. The central question is when organisms with conflicting interests should be expected to communicate "honestly"...
of need; the signal's costliness for the depressive certifies its honesty. Finally, for social partners who find it uneconomical to respond helpfully to an honest signal of need, the same depressive symptoms also have the potential to extort relevant concessions and compromises. Depression’s extortionary power comes from the fact that it retards the flow of just those goods and services such partners have come to expect from the depressive under status quo socioeconomic arrangements.
Thus depression may be a social adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....
especially useful in motivating a variety of social partners, all at once, to help the depressive initiate major fitness-enhancing changes in their socioeconomic life. There are diverse circumstances under which this may become necessary in human social life, ranging from loss of rank or a key social ally which makes the current social niche uneconomic to having a set of creative new ideas about how to make a livelihood which begs for a new niche. The social navigation hypothesis emphasizes that an individual can become tightly ensnared in an overly restrictive matrix of social exchange contracts, and that this situation sometimes necessitates a radical contractual upheaval that is beyond conventional methods of negotiation. Regarding the treatment of depression, this hypothesis calls into question any assumptions by the clinician that the typical cause of depression is related to maladaptive
Adaptive behavior
Adaptive behavior is a type of behavior that is used to adjust to another type of behavior or situation. This is often characterized by a kind of behavior that allows an individual to change an unconstructive or disruptive behavior to something more constructive. These behaviors are most often...
perverted thinking processes or other purely endogenous sources. The social navigation hypothesis calls instead for analysis of the depressive’s talents and dreams, identification of relevant social constraints (especially those with a relatively diffuse non-point source within the social network of the depressive), and practical social problem-solving
Problem solving
Problem solving is a mental process and is part of the larger problem process that includes problem finding and problem shaping. Consideredthe most complex of all intellectual functions, problem solving has been defined as higher-order cognitive process that requires the modulation and control of...
therapy
Psychotherapy
Psychotherapy is a general term referring to any form of therapeutic interaction or treatment contracted between a trained professional and a client or patient; family, couple or group...
designed to relax those constraints enough to allow the depressive to move forward with their life under an improved set of social contracts. This theory has been the subject of criticism..
Prevention of infection
It has been hypothesized that depression is an evolutionary adaptation because it helps prevent infectionInfection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
in both the affected individual and his/her kin.
First, the associated symptoms of depression, such as inactivity and lethargy, encourage the affected individual to rest. Energy conserved through such methods is highly crucial, as immune activation against infections is relatively costly; there must be, for instance, a 10% increase in metabolic activity for even a 1℃ change in body temperature. Therefore, depression allows one to conserve and allocate energy to the immune system more efficiently.
Depression further prevents infection by discouraging social interactions and activities that may result in exchange of infections. For example, the loss of interest discourages one from engaging in sexual activity, which, in turn, prevents the exchange of sexually transmitted diseases. Similarly, depressed mothers may interact less with their children, reducing the probability of the mother infecting her kin.
Lastly, the lack of appetite associated with depression may also reduce exposure to food-borne parasites.