THE SOCIAL COMPETITION HYPOTHESIS OF DEPRESSION
John Price, Leon Sloman, Russell Gardner Jr,
Paul Gilbert and Peter Rohde
Depressive personality and depressive
illness are examined from an evolutionary, adaptationist, standpoint. It is postulated that the depressive state
evolved in relation to social competition, as an unconscious, involuntary
losing strategy, enabling the individual to accept defeat in ritual agonistic
encounters and to accommodate to what would otherwise be unacceptably low
social rank. Some implications for
research and treatment are discussed.
There is some agreement that depressive states
represent "a psycho-biological response pattern" which is part of the
inherited behavioural repertory of the human organism (Lewis, 1934; Hill, 1968;
Beck, 1987; Nesse, 1990; Gilbert, 1992; Powles, 1992). This means that depression performed some
function over the course of our evolution and that those of our ancestors who
had the capacity to become depressed survived at the expense of those who did
not. However, it is easier to agree that
there was a function than to agree on what that function was. To ignore the problem would be to limit our
understanding of the biology of depression and possibly forego pointers to
research into etiology, classification and treatment.
Performance
is limited in depression. There is impairment of perception, of execution and
of the central processes which mediate between perception and execution,
experienced as difficulty in making decisions (Radford et al., 1986). Even in mild depressions there is some
impairment, particularly for tasks requiring initiative.
Impairment
of performance is not incompatible with a biological function. Performance is impaired in sleep and
hibernation; viewed out of the context of circadian and circannual change we
might be sceptical of their adaptive value.
It is
in relation to social competition that depression can be seen to exercise a
function (Price, 1967; Sloman, 1976; Gardner, 1982; Sloman, Gardner &
Price, 1989; Gilbert, 1992). The result
of competition is that winners and losers behave differently, and it may be
that mood change is the mechanism that mediates this variation in behaviour.
Identification
of depression as a component of a behavioral system which we share with other
animals anchors our subject firmly to the basic disciplines of comparative
ethology (the study of behaviour as it occurs in nature) and behavioral ecology
(the analysis of behaviour in terms of function), thus supplementing the
pioneering work of John Bowlby on attachment behaviour (Goldberg, 1991).
Recent
work in behavioral ecology has been concerned with situations in which an
animal utilises only one from a set of two or more alternative behavioral
strategies (Krebs & Davies, 1987).
Depression may be identified as a losing or de-escalating strategy and
elevation of mood as a winning or escalating strategy.
Since adopting a losing strategy often implies foregoing resources which
may contribute to reproduction, depression might also fall into the category of
altruistic behaviour which has been of interest in recent evolutionary theory
(Hamilton, 1963; Krebs, 1987).
Finally,
the mathematical analysis of animal contest behaviour requires a variable to
express the animal's knowledge of its own fighting capacity. This animal self-concept has been termed
"resource-holding potential" (RHP) and may be the evolutionary
primordium of human self-esteem (Parker, 1974; Wenegrat, 1984; Archer, 1988). RHP determines whether an animal escalates a
confrontation and attacks, or de-escalates and adopts the "involuntary
subordinate strategy" which we think may be the primordium of depressive
states. Thus we are able to use the
tools of behavioral ecology in the analysis of the mutual interaction of self-esteem
and mood change, which permeates much of psychiatric practice.
Statement of the
hypothesis
The social competition hypothesis of depression
is that human beings share with their more primitive ancestors a mechanism for
yielding in competitive situations. This
"involuntary subordinate strategy" has three main functions: (1) an executive function which prevents the
individual from attempting to make a "come-back" by inhibiting
aggressive behaviour to rivals and superiors (but not to dependents) and by
creating a subjective sense of incapacity;
(2) a communicative function which signals "no threat" to
rivals and "out of action" to any kin or supporters who might wish to
push the individual back into the arena to fight on their behalf; and (3) a facilitative function which puts
the individual into a "giving up" state of mind which encourages
acceptance of the outcome of competition and promotes behaviour which expresses
voluntary yielding. This leads to
reconciliation and the termination of whatever conflict triggered the
"involuntary subordinate strategy".
But if voluntary yielding is blocked for any reason, the involuntary
subordinate strategy may become intense and prolonged and may be recognised as
depressive illness.
Social
competition can be described at a number of different levels and the hypothesis
relating depression to social competition can be expressed in terms of each
level, as follows.
Sexual selection
a)
death, rare in vertebrates, common in invertebrates, e.g. spiders (Huntingford
and Turner, 1987).
b)
physiological suppression of sexual development, as occurs, for example, in the
naked mole rat and in some
c)
inhibition of sex change, so that the subordinate individual is maintained in
the opposite sex by the signals of the dominant individual, as occurs in some
fish (Keenleyside, 1979).
d)
some psychiatric syndromes, including the phenomena we recognise clinically as
depression. This depression could occur
as a lifelong phenomenon, in the form of depressive personality, in the case of
those who are never successful, or as an episode of depressive
"illness" in those who achieve success and then lose it.
Social hierarchy
The social roles of successful and unsuccessful
animals are represented in two different but related ways. In some species the two contrasting roles are
"territory owner" and "non-territory owner". In other species they are high-ranking and
low-ranking within a social hierarchy.
We
suggest that depression is a component of the behavioral strategy evolved for
the role of non-territory owner and low-ranker.
We
would expect to find depression manifesting in the form of both illness and
personality reflecting the fact that some individuals achieve ownership and/or
high rank and then lose it, whereas others have never achieved these objectives
in the first place.
A
social hierarchy performs two different functions. First, it regulates the transfer of power and
of breeding opportunities from one generation to the next. Second, it stratifies each generation in
terms of power and breeding opportunities, and it is this second function which
mediates sexual selection.
The
simplest hierarchy is the asymmetrical, two-person relationship. There are many ways of negotiating the
one-down position in such a relationship (Price, 1988, 1992a) and these may be
associated with perceptual and cognitive distortion in the one-down
member. There may be adulation in which
the status of the one-up member is magnified, and there is depression in which
the status of the one-down member is diminished. Both ensure a stable complementarity of the
relationship and avoid the disruptive "arms race" of symmetrical
schismogenesis (Bateson, 1972). Unlike
adulation, the depressive mechanism allows for a switch in one-upness, when
chronic depression in the formerly one-down member may be replaced by an acute
depression in the formerly one-up member (Price, 1991). The association of depression with loss of
social rank in animals has been discussed for birds (Price and Sloman, 1987),
monkeys (Price, 1989) and lizards (Price, 1992b).
Ritual agonistic behaviour
Ritual agonistic behaviour is the social
interaction which produces these role asymmetries in the majority of vertebrate
species. An encounter between
competitors is followed by ritualised fighting.
The ritualisation reduces the physical risk to both parties. The losing behaviour is as ritualised as the
fighting. Depression can be seen as a
ritual form of losing behaviour producing temporary psychological incapacity
which signals submission to the winner but preserves the loser without physical
damage. It performs the function which
death performs in unritualised fighting, and which the referee performs in
culturally ritualised competition.
Resource-holding potential (RHP)
Agonistic behaviour can be described in terms
of a self concept called resource-holding potential (RHP) (Parker 1974,
1984). RHP is an estimate of fighting
capacity by both the individual and others.
Size, strength, skill, previous success, weapons and allies, all
indicate increased fighting capacity.
The output from a high self-perception of RHP is threat or attack.
All
the phenomena of ritual agonistic behaviour can be described in terms of
signals of either absolute or relative RHP (Price, 1988). Ritual agonistic behaviour can then be
conceptualised as an RHP management system which produces a rank order of
individuals according to differences in RHP.
Self-esteem
is the nearest we can get to RHP in human terms, and our hypothesis is that
self-esteem evolved out of RHP. This would
explain two aspects of self-esteem which would seem to be puzzling: its global nature and the great variation in
self-esteem in the population (Lancet, 1988);
both these features are essential to the function of RHP. Re-phrasing our hypothesis in terms of RHP,
we can state that depression in its chronic form is a function of low RHP, and
in its acute form a function of falling RHP.
If we now substitute self-esteem for RHP, and also adopt the current
ethological practice of regarding behavioral variation as alternative
strategies, we can formulate depression as a low self-esteem strategy.
It
may be asked how such a system can evolve, when all the advantage seems to be
on the side of the high self-esteem strategy.
In fact the advantages of the two strategies are likely to be equalised
by negative frequency-dependent selection, as has been shown by Maynard Smith
(1982) using what is known as evolutionary game theory. He calls the high self-esteem strategy a "hawk"
strategy which is characterised by escalation of agonistic encounters, and the
low self-esteem strategy a "dove" strategy which is characterised by
de-escalation. He has demonstrated in
his evolutionary model that, given certain conditions, a pure hawk strategy is
not "evolutionarily stable", in that it can be infiltrated by a mixed
hawk/dove strategy. In this model it is
assumed that in encounters between hawk and dove the hawk has the higher
pay-off, in terms of survival and reproduction; but when hawk meets hawk, the
payoff is lower because of the risk of escalation to unritualised combat with
consequent serious injury or death.
Yielding ensures the loser survives.
The
low self-esteem strategy can be seen as a form of altruistic behaviour which
promotes the survival and reproduction of close relatives and so raises
"inclusive fitness" (Hamilton, 1963; Krebs, 1987). In fact, an alternative term for the low
self-esteem strategy might be "kin-helper strategy" contrasting with
the "self-helper" high self-esteem strategy.
Human Social Competition
We have presented the yielding hypothesis in
terms of ritual agonistic behaviour, suggesting that the mechanisms of
depression evolved when ritual agonistic behaviour was the principle form of
social competition underlying sexual selection, as it is in most vertebrate
species today. However, ritual agonistic
behaviour is not the main form of human social competition. As pointed out by Barkow (1990) and by
Gilbert (1992), competition by attraction has largely replaced competition by
intimidation, and is the main form of competition seen in primitive tribes by
anthropologists. In order to achieve the
prestige which guarantees reproductive success (usually the possession of more
than one wife in the case of males, and marriage of children to high-ranking
partners in the case of females), individuals have to make themselves
attractive to others, either to their peers or to particular patrons, and it is
the latter who make the decisions which determine the differential allocation
of rank.
If it
were not for the findings of ethology, it would be doubtful whether we would
recognise ritual agonistic behaviour as occurring in human beings. Agonistic behaviour and social asymmetries
have been ascribed to cultural factors, or to the carry-over into adult life of
the parent-child asymmetry and the punishment which is a common component of
child-rearing. Such was the view of
Freud, who did not have the benefit of the ethological descriptions of
agonistic behaviour and social asymmetry in such a wide variety of vertebrate
species, including many reptiles who have no parent-offspring contact at
all. Thus it was natural for him to
conceptualise the neuroses associated with adult power struggles in terms of
unresolved nursery conflicts, a view which was corrected by neo-Freudians such
as Sullivan and Horney (Birnbach, 1962); but even the latter saw adult conflict
in cultural terms, and did not conceive that mankind might share with animals a
phylogenetically old mechanism for creating social asymmetry between previously
equal adults.
Accounting for the Features of Depression
Our hypothesis is concerned with
"ultimate" causes (the function of the "involuntary subordinate
strategy" during evolution) and is therefore to some extent independent of
proximal causes. However, it is
compatible with what is known about the social origins of depression (Brown et
al., 1986; Powles, 1992; Kendler et al., 1993), and it is only the constraint
of space which prevents us from pursuing at length this interesting topic.
Proponents of an evolutionary hypothesis of any psychiatric condition
also have a duty to show that it is consistent with the known features of the
condition and that these features can perform the postulated function. In fact, the social competition hypothesis is
the only evolutionary hypothesis which accounts for the incapacity of
depression; indeed, we see the incapacity as the main functional feature of
depression, which is hypothesised to be a ritual (psychological) substitute for
the physical damage which is suffered by the loser of an unritualised contest.
The
social competition hypothesis also accounts for the cognitive distortions of
depression. Beck (1967) described a triad of distortions in which there are
negative views of the self, the world and the future. These distortions are compatible with a
"de-escalating" state of mind.
The depressed self is not a strong "favourite" for successful
competition; the world of the depressive is not a favourable arena for
competing; and the pessimism of the depressive is in stark contrast to that
optimism which seems to be required for successful competition. The depressive
is not only pessimistic about the future, but has a distorted view of the past
in which former rank, ownership and success seem to the patient like a sham,
and therefore not to be regained.
Apart
from ownership and RHP, the only variable which is important in the
mathematical analysis of agonistic behaviour is "resource value"
which expresses the value of whatever is being fought about (Parker, 1984). The lower the resource value to a contestant,
the more likely he is to yield (flee or submit) rather than to attack. In depression there is a generalised
reduction in the perceived value and significance of all goals and incentives,
which is usually described as loss of interest.
The depressive loss of interest favours de-escalation of conflict. If the resource under consideration is the
general one of social rank and success, then reduction in resource value is
synonymous with loss of pride and ambition.
We
feel that our hypothesis accounts for most of the features of depressive
states. In particular, it accounts for
the incapacity suffered by depressed patients and for the distortions in their
thinking, features which are not explained by theories which see the function
of depression to be the conservation of resources (Beck, 1987; Powles, 1992),
the management of investment in the environment (Nesse, 1990), the
relinquishing of unrealisable goals (Klinger, 1975, Hamburg et al., 1975) or
the redressing of imbalance in reciprocal exchange (Glantz and Pearce, 1989).
Our
hypothesis is consistent with subjective heterogeneity in depression. It does not matter whether yielders refrain
from fighting back because they are too tired, or too frightened, or feel too
physically ill, or think they will not win, or that they do not deserve to win,
or that their allies will not come to their support.
Ethological observations of depressed patients show that active
(spontaneous, person-oriented) submission such as flattery is reduced, but
passive submission such as looking down is increased (T. Schelde, personal
communication, 1993); which highlights
the difference between the "involuntary subordinate strategy"
underlying depression and the voluntary subordinate behaviour which may
pre-empt or replace it.
Epidemiological features
Our hypothesis is consistent with the fact that
depression is more common, more severe and more prolonged in later life, for
the most important acts of yielding are required when one generation is giving
way to the next. We have dealt elsewhere
with the fact that depression tends to follow "exit" events such as
bereavement, whereas it might be expected that yielding would more often be
required following the entry of new members to the group (Price, 1988). We argue that social rank is so dependent on
the support of others that loss of significant others has become the main
predictor of loss of rank. The
dependence of rank on support from kin and other allies is a widespread characteristic
of non-human primates (De Waal and Harcourt, 1992), suggesting that it may have
applied to the simian and human common ancestor some 40 million years ago,
allowing sufficient evolutionary time for close interconnections to develop
between the brain mechanisms subserving agonistic and affiliative behaviour.
We
have also (Price, 1988) dealt with the problem that depression is commoner in
women than men, whereas agonistic behaviour is thought to be more common in
males. Our argument is that agonistic
behaviour is more conspicuous but not more common in males, and, in any case,
there is evidence that when women have equal opportunities, the female excess
of depression disappears (Wilhelm and Parker, 1989).
Implications
for Research
Animals
Our hypothesis suggests a wide choice of animal
models for research into depression. Low
rank and falling rank in animals have been used as models for human physical
disease, such as heart disease (Henry and Stevens, 1986) and renal disease
(Holst, 1986) and it would be surprising if social stress intense enough to
produce these physical pathologies was innocent of inducing
psychopathology. In his work on social
stress in tree shrews, Holst (1986) has observed two distinct forms of reaction
to subjugation, one associated with increased adrenomedullary activity and one
with adrenocortical activity, the latter showing extreme social withdrawal
ending in death; these reactions in tree
shrews bear a resemblance to the contrasting fight/flight and conservation/withdrawal
clinical syndromes described by Powles (1992).
In
equally promising work on guinea pigs, Sachser and Lick (1991) have shown that
being brought up in a colony (as opposed to with a single female) abolishes the
aggression which occurs when two strange males are put together in the presence
of a female. This suggests that the
experience of living with other males during adolescence may create the
variation in resource-holding potential (RHP) which is required to avoid
pairwise contests among adults. They
also made the observation that the loser of a contest could be predicted from
changes in the status of his adrenal and other hormones before there was any
detectable change in his fighting behaviour;
this supports Leshner's (1983) hypothesis that the switch from
escalation to de-escalation involves a positive feedback loop which includes
the adrenal cortex.
Some
animals are promising for research because they show physical effects of rank
change. Some reptiles and fish and at
least one monkey change colour following rank change (Price, 1989), some fish
change sex (Keenleyside, 1979). These
might not only be possible markers for mood change, but they offer a path by
which the mechanism responsible for the physical changes might lead to the central
mechanism. Both low rank and depression
are associated with increased activity of the
hypothalamic-pituitary-adrenocortical axis, and there is an interesting
association between rank and indoleamine metabolism in both monkeys (McGuire,
1988) and fish (Winberg & Nilsson, 1993).
A project currently under way in the Department of Psychiatry of the
University of Tasmania is using low rank in a marsupial called the Sugar Glider
as a model for depression (I.H. Jones and J. Mallick, personal communication,
1992).
Human beings
Our hypothesis that depression evolved out of
mechanisms mediating ranking behaviour throws a new light on the extensive work
which has been carried out on the expression of hostility in depression, and
which has produced very conflicting results (Riley et al., 1989). Some workers have found that depressed
patients express more anger than controls (Fava et al., 1993), and this might
seem to conflict with our idea that depression functions to inhibit aggression.
In
fact, our hypothesis states that only hostility to equal and higher ranking
people is inhibited, whereas hostility expressed to lower ranking people is
often increased; and it is our clinical
impression that hostility in depression is usually unexpressed or "taken
out" on the furniture, or expressed to subordinate spouses or
children. No published study to date has
considered whether the hostility is felt or expressed to a higher ranking or a
lower ranking person. Yet from an ethological perspective, the expression of hostility
up a hierarchy is a very different matter from expressing it downwards. Our hypothesis predicts that, if depression
occurs in one partner in a complementary relationship, hostility expressed by
the patient to the other will be increased if it is the dominant partner who
gets depressed, but will be reduced if it is the subordinate partner who gets
depressed.
Implications for Treatment
Analysis of the patient's situation
The yielding hypothesis helps the physician to
explore the patient's situation, identify any conflictual relationships and
assess the reasons for non-resolution of any agonistic interaction. There are five options:
1. The
conflict may be resolved by negotiation and compromise. Here we are talking in terms of
reconciliation, which implies penitence, atonement, forgiveness and other forms
of negotiation.
2. The
patient may be helped to win the conflict.
This applies particularly to patients who are insufficiently
self-assertive.
3. The
patient may be assisted to substitute voluntary yielding in the form of
conscious submission for the involuntary and unconscious yielding of
depression.
4. The
patient may be enabled to leave the arena.
This may involve physical separation from the adversarial person and
certainly involves mental detachment.
15. Help may come from reducing the patient's
assessment of the value of the resource being competed for. Aspirations may be
excessive or too narrow, the patient having "all his eggs in one
basket". These are concerns common
to psychotherapy, philosophy and religion.
Sharing with the patient
It may or may not be desirable to share the
yielding hypothesis with the patient;
for instance, the therapist might say: "Your depression is serving
an important function in your marriage, it is enabling you to submit to your
husband's demands without rebellion, and is therefore saving your relationship
from probable rupture." This is a
form of "positive connotation" of the symptom, a technique widely
used in family therapy; and it is also a reframing from the patient's previous
formulations which may have been in terms of hormones or physical illness. It is also something of a challenge,
suggesting to her that she need not submit to her husband's demands, and puts in
her mind the idea that there may be alternative ways of dealing with those of
her husband's demands which she finds unacceptable.
To
patients of a more scientific frame of mind, it may help simply to explain what
is going on, since lack of meaning adds yet another morbid dimension to the experience
of depression. We sometimes use the
analogy of hibernation, explaining that while hibernation is nature's way of
helping certain animals to survive unfavourable weather conditions, depression
is nature's way of helping certain humans to survive unfavourable social
conditions. This is often acceptable to depressed patients, who may themselves
feel like curling up into a ball in a hole in the ground and staying there for
a long time. And the seasonal recovery from
hibernation helps the patient to believe in the likelihood of remission.
On
the other hand, often the situation can be resolved without the patient being
aware of conflict. Haley (1963), for
instance, advocates the resolution of agonistic situations in marriage by means
of non-agonistic interpretations, such as parent/child interaction, and we
would endorse this view.
Relation to other psychotherapies
Our evolutionary perspective supports those
therapies aimed at resolving interpersonal conflict (Karasu, 1990; Stravynski
and Greenberg, 1992) and the various schools of family therapy which are
sensitive to deviations of hierarchy such as cross-generational coalitions
(Haley, 1963).
Cognitive
behaviour therapy appears to us to be a means for raising RHP and other
components of self-esteem and of rendering the basis for these self-appraisals
realistic. Both these aims are supported
by our approach. We think our main
contribution is the conceptualisation of depression as a fail-safe strategy to
which there are alternatives at higher levels of mental organisation. Whereas psychoanalysis aims to render
unconscious thoughts conscious, therapy based on evolutionary principles aims
to replace unconscious behavioral strategies with conscious ones.
Acknowledgement
This paper is dedicated to Dr. M.R.A. Chance
whose insight into the relation between agonistic behaviour and psychopathology
stimulated the train of thought summarised above.
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*John Price, D.M., M.R.C.P., F.R.C.Psych., Odintune
Place, Plumpton, E. Sussex, BN7 3AN;
Leon Sloman, F.R.C.P.(C), Associate Professor, Clarke Institute of
Psychiatry, Toronto, Canada; Russell
Gardner, Jr, M.D., Professor of Psychiatry, University of Texas Medical
Branch, Galveston, Texas, U.S.A., Paul Gilbert, Ph.D., F.B.Ps.S, Professor
of Clinical Psychology, Derby University;
Peter Rohde, M.B., B.Ch., F.R.C.P.(E), F.R.C.Psych., 53 Harley
Street, London W1N 1DD.
*Correspondence: Department of Psychiatry,