Contents:

As Extremes of Normal Emotions

Charles Darwin wrote in 1876: 

If all the individuals of any species were habitually to suffer to an extreme degree, they would neglect to propagate their kind; but we have no reason to believe that this has ever, or at least often occurred. Some other considerations, moreover, lead to the belief that all sentient beings have been formed so as to enjoy, as a general rule, happiness. "Everyone who believes, as I do, that all the corporeal and mental organs (excepting those which are neither advantageous nor disadvantageous to the possessor) of all beings have been developed through natural selection, or the survival of the fittest, together with use or habit, will admit that these organs have been formed so that their possessors may compete successfully with other beings, and thus increase in number. Now an animal may be led to pursue that course of action which is most beneficial to the species by suffering, such as pain, hunger, thirst, and fear; or by pleasure, as in eating and drinking, and in the propagation of the species, etc.; or by both means combined, as in the search for food. But pain or suffering of any kind, if long continued, causes depression and lessens the power of action, yet is well adapted to make a creature guard itself against any great or sudden evil. Pleasurable sensations, on the other hand, may be long continued without any depressing effect; on the contrary, they stimulate the whole system to increased action. Hence it has come to pass that most or all sentient beings have been developed in such a manner, through natural selection, that pleasurable sensations serve as their habitual guides. We see this in the pleasure from exertion, even occasionally from great exertion of the body or mind,--in the pleasure of our daily meals, and especially in the pleasure derived from sociability, and from loving our families. The sum of such pleasures as these, which are habitual or frequently recurrent, give, as I can hardly doubt, to most sentient beings an excess of happiness over misery, although many occasionally suffer much. Such suffering is quite compatible with the belief in Natural Selection, which is not perfect in its action, but tends only to render each species as successful as possible in the battle for life with other species, in wonderfully complex and changing circumstances. "That there is much suffering in the world no one disputes. Some have attempted to explain this with reference to man by imagining that it serves for his moral improvement. But the number of men in the world is as nothing compared with that of all other sentient beings, and they often suffer greatly without any moral improvement. This very old argument from the existence of suffering against the existence of an intelligent First Cause seems to me a strong one; whereas, as just remarked, the presence of much suffering agrees well with the view that all organic beings have been developed through variation and natural selection.  (Darwin, 1887)

Randolph Nesse of the University of Michigan's Department of Psychiatry, argues for an evolutionary (rather than proximate) explanation of the several functions of mood.  He considers mood to be coordinated specialised states shaped to cope with situations of high and low propitiousness i.e. mood is a reflection of the perceived propitiousness of current circumstances.  

Nesse argues that emotions serve to promote adaptive behaviour by motivating actions & goals, as most thoughts, plans & actions are intended to induce positive emotions or to avoid negative emotions.  Emotions can be defined as modes of operation shaped by NS to adjust physiological, psychological (cognitive) & behavioural parameters of the organism to increase its capacity & tendency to respond adaptively to (cope with) threats & opportunities in certain situations (adaptive challenges that occurred repeatedly in the course of evolution).  

Specifically, Nesse proposes that high mood helps individuals take advantage of propitious situations & low mood motivates them to seek help, be socially submissive, conserve resources and consider alternative strategies in situations where investments are not paying off (Nesse, 1990, 1991).  Nesse (1990) argues for a correspondence between specific emotions & specific situations that elicit the emotion.  He likens emotions to selected hard-wired software programs for the mind.  However, he notes differences such as that different emotions can be aroused to different degrees all at once.  

(Nesse, 2000) differentiates "depression", which he defines as severe states of negative affect that are often but not necessarily pathological, from "low mood", which refers to mood states in the common range of normal experience.  He suggests that NS may have gradually & partially differentiated a generic state of inhibition into subtypes specialised to cope with particular kinds of situations, leading to overlapping states such as sadness, grief, demoralisation, guilt & boredom.  Nesse argues that the intrinsic aversiveness of most low mood & depressive states suggests that they may be related to a defense, just as aversive defenses such as pain, nausea & fatigue are likely to be the product of NS due to their tendency to promote escape & avoidance of situations that decrease fitness.  Further evidence can be found in the epidemiology of depression, which indicates that depressive disorders are common, with constituent symptoms that most people have experienced, & which arise frequently at ages where reproductivity peaks.  He also notes the frequent relationship between loss & negative affect, & the proportionality of low mood to the magnitude of the loss.  

Nesse (1990) argues that depressive & anxiety disorders are extreme versions of sadness & fear (normal defenses).  He argues that pathological depression is caused by low mood being expressed excessively, in a prolonged manner, or in the wrong situation.  Nesse (2000) notes that whilst 80% of first episode depressions in women are preceded by a severe life event, onset of depression tends not to be preceded by severe life events for third & subsequent episodes, suggesting that not all depressive episodes are defenses.  

Leon Sloman (1992) of the University of Toronto & Clarke Institute of Psychiatry, emphasises the social functions of mood.  He proposes that low mood has the double function of triggering behavioural subroutines within the individual & communicating to others.  This distinction between internal & external functions of mood follows the traditional separation between the communicative & motivational functions of mood.  Nesse (1992) notes that "subjective" aspects of mood are sometimes treated as a third category, a cognitive function, to reflect additional functions that arise for internal states that are consciously experienced.  

Sloman (1992) suggests that mood variation plays a crucial role in the regulation of aggressive behaviours necessary for survival.  The feelings of inadequacy, discouragement & hopelessness that characterises low mood may be designed to turn off aggression within the individual as well as to inhibit aggression directed by others towards that individual.  The low mood response may enable a separated infant to pass from Bowlby's stage of protest (an aggressive response) to depression (withdrawal or submission from internalising the bad object), to elicit sympathy from others.  It therefore serves the function of ending an agonistic conflict by causing individuals who are losing to submit to their opponents.  This enables them to elicit sympathy, perhaps from the same individuals they were previously challenging.  He argues that there may be a sequence of affective states (behavioural subroutines), each state being specifically programmed to switch off the previous one.  He suggests that low mood turns off bad mood, which leads to obtaining nurturing, ending the conflict, submitting, getting out of the situation, or ending frustration by giving up unrealistic goals.  This allows the individual to engage in activities that may be more productive and therefore mood elevating.  He suggests that the high mood of the winner terminates aggression & facilitates acceptance of the opponent's act of submission, which brings the conflict to an end.  It contributes to an increase in self-confidence, which encourages the winner to tackle new challenges & may promote that individual's chances of being successful in future conflicts (Sloman, 1992).  

Another view of mood function is that mood variation may assist individuals to attain an appropriate position in the social hierarchy, which helps them develop realistic goals to be more productive.  If people with particular skills fail to have those skills recognised & are trapped in a low position in a hierarchy, this may create frustration for them because they cannot express their talents in a productive fashion.  If they are too high in the hierarchy they are also likely to experience frustration & failure, because they lack the necessary competence to maintain their position.  The reluctance of most people to give up power or status seems to be associated with the fact that the loss of one's position in a hierarchy usually generates low mood.  Individuals obtain information about their competitor's talents or skills through competitive struggles.  Success leads to high mood, encouraging further efforts in that arena, their skills becoming recognised by the group & their rising in that hierarchy.  This provides a good opportunity for their further developing & utilising their talents for the benefit of the group.  For example, in hunter-gatherer society the group will benefit by being able to recognise those who are potentially the best trackers, warriors or weapon makers and to encourage them to develop their skills.  If the individual tries his hand at an activity for which he is unsuited, his consequent low mood would discourage him from further efforts in that direction and encourage him to try to succeed in another arena where he could more productive (Sloman, 1992).

Hartung (1988) has suggested that low self-esteem may often be a deception (and self-deception) that allows one to keep a position in the hierarchy without threatening the higher-ups.

Lazarus (1991) defines emotions as "complex, patterned, organismic reactions to how we think we are doing in our lifelong efforts to survive & flourish & to achieve what we wish for ourselves".  "They express the intimate personal meaning of what is happening in our social lives & combine motivational, cognitive, adaptational, & physiological processes into a single complex state that involves several levels of analysis".  He argues for a systems rather than reductionist view, in that "emotion cannot be divorced from cognition, motivation, adaptation, & physiological activity".  He emphasises that "one must remember that, above all, emotions are individual phenomena & display great variations among individuals ... an emotion happens to a person with a distinctive history who wants, thinks, & confronts specific environments, evaluates their significance, & acts as adaptively as possible".  

Morris (1992) defines mood as a cue to the individual about the resources available to meet environmental demands.  He considers how a functional analysis of mood can help to explain diurnal and seasonal patterns of mood, mood-congruent memory and perception, the relation of mood to self-focussed attention (Ingram, 1990), and various aspects of the major affective disorders.  

LeDoux argues that emotions can have both useful & pathological consequences.  He notes that our emotions can become maladaptive when fear becomes anxiety, desire gives way to greed, annoyance to anger, anger to hatred, friendship to envy, love to obsession (fixation) or pleasure to addiction.  He suggests that this tendency towards emotional disorder occurs because, "While conscious control over emotions is weak, emotions can flood consciousness.  This is so because the wiring of the brain at this point in our evolutionary history is such that connections from the emotional systems to the cognitive systems are stronger than connections from the cognitive systems to the emotional systems" LeDoux (1996).  

Wilson (2001) argues that the nosological meaning of "depression" is likely to be a syndromic composite of homologous genetic traits, phenocopies and proximate mechanisms.  He suggests some underlying genotypy of depression is too common not to have been selected. 

Wilson (2002) suggests that much mood psychopathology refers to phenotypic variants of past epigenetic adaptations, most of which regulated social rank hierarchies or sexual selection.   He argues that mood disorders result from extremes of normal evolutionary stable strategies that evolved in evolutionary stages.  He suggests that depression is the equivalent of yielding or de-escalating social conflict and mania is related to escalation to acquire resources (as per MacLean & Stevens & Price). 

Depressive Disorders

As a Disorder of the Affiliation & Bonding Archetype

Stevens & Price (2000) classify mood disorders as loss of attachment : pathogenic parenting causing neurotic symptoms.

As a Disorder of the Hierarchical Ranking Archetype

Stevens & Price (2000) classify mood disorders loss of rank : lowered resource holding potential, competition for resources or loss of territorial ownership.

As a Disorder of the Courtship & Mating Archetype

As a Disorder of the Threat Response Archetype

As a Disorder of Conflict Within the "Triune" Brain
(causing "maladaptive" depression)

Stevens & Price (2000) suggest there are two vertebrate strategies for dealing with adversity: the escalation or winning strategy  (attack, "win at all costs") and the de-escalating or losing strategy (to yield, submit & "cut one's losses", to achieve adaptive depression).  Either strategy, depending on the context, may lead to adaptive outcomes for the organism.

MacLean (1985) suggests that each of the three central processing assemblies of the triune brain has the autonomous power to select either a winning or a losing strategy:

Maladaptive Depression occurs when all three "central processing assemblies" are not pulling together towards the same objective, enabling a decisive win or a total withdrawal from the external stressor.  The conclusion must be to force the patient to adopt a unified losing strategy at all three brain levels.

Stevens & Price (2000) suggest that maladaptive depression requires pharmacotherapy whereas adaptive depression requires psychotherapy.

As a Disorder of "Blocked Higher Level Losing"
(or Involuntary Yielding in Social Competition)

Akiskal (1996) notes that dysthymia lacks the classical 'objective' or 'major' signs of acute clinical depression, such as profound changes in psychomotor and vegetative functions.  Instead, patients consult their doctors for more fluctuating complaints such as gloominess, lethargy, and self-doubt.  As a result, in the past they were labelled "existential depressives" or "depressive characters".  Several lines of research over the past 15 yrs have shed new light on the biological origins of this disorder.  Sleep neurophysiologic findings have shown that many parameters of paradoxical sleep in dysthymia (such as REM percentage, REM latency, and circadian distribution of REM) are similar to those observed in major affective illness.  Furthermore, family studies of dysthymia have shown a significant excess of mood disorders.  Akiskal suggests, based on sleep findings, family and follow-up data, that dysthymia be considered as "trait depression," a constitutional variant of major affective depression.

Akiskal (2002) suggests that the melancholic temperament reflects sensitivity to suffering and evolved because empathy was important for group cohesion & the accompanying obsessive-compulsive traits promoting of work.  He suggests the stereotype of the unipolar  hard-working philosopher. 

Bipolar Disorders

Akiskal (2002) suggests that mood disorders may be the result of extreme traits or pathological combinations of personality traits.  Hyperthymic, cyclothymic or irritable personality traits are common in bipolar people.  The irritable/explosive temperament may be more on the side of pathology.  Achievement and creativity may be a dilute form of bipolar disorder, as these capacities are evident in bipolar patients between their acute mood episodes.  There have been studies of non-ill relatives in families of people with bipolar disorder that support the view that capacity for achievement and creativity may represent a dilute form of the genes and premorbid temperaments of bipolar disorder.  Music, performing arts and poetry may have evolved to attract the opposite sex, just as a peacock evolved its bright plumage secondary to sexual selection.  Leadership qualities may relate to dilute bipolar traits and have evolved to better face challenges to the group from within and without to increase group stability & keep the group together.  This may have been necessary for risk taking & exploration, on behalf of the social group, & exploration of potential mates.  

The flamboyant behaviour & restless pursuit of romantic opportunities in cyclothymia suggests that its constituent traits may have evolved as a mechanism of sexual selection.  Their creative bent for  poetry, music, painting and fashion design may have evolved to subserve such a mechanism (Akiskal, 2000). 

Wilson (2002) argues that bipolar disorder is an epigenetic disease as it clusters in families & has a high rate of twin concordance & like sickle cell anaemia, the first genetic disease that was shown to have evolved for its adaptive genes protecting against malaria in homozygotes, has a high morbidity & mortality, which makes it hard to understand why it is so common (0.5% for the Kraeplinian classification & 6% for the extended bipolar spectrum disorder).  Wilson calculated that the narrow Kraeplinian category is 50 times as common as predicted to occur from classical population genetics (Hardy-Weinberg) & thousands (possibly as high as 12,000) times for those who would be categorised as having a variant of the bipolar spectrum disorder, when taking the prevalence/frequency in the context of the maximum mammalian CNS mutation rate.  He argues that this data argues that the genes for bipolar disorder were selected early in human or prehuman life.  Wilson argues that the selection relates to "socio-physiology".  At the end of the Ice Age 15,000 years ago, changed climate encouraged the rise of agriculture, which led to humans living more densely.  The "phenotypic reaction" was for less flexible genes to be deselected.  

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Citation suggestion: Dr Gary Galambos, Mood Disorders, Evolutionary Psychiatry Home Sydney Australia (http://www.ep.org.au/dis/mood.htm) [date accessed]

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