The Evolutionary Significance Of Affective Temperaments 

Introduction

An evolutionary perspective is not part of the thinking repertoire of a psychiatrist when faced with a mentally ill patient. Nonetheless, such an approach has been developing on the sidelines of psychiatry with potentially very important contributions to understanding why mental disorders exist. Unfortunately, while promising, Darwinian psychiatry is fraught with methodologic difficulties. Unlike the record of somatically transmitted traits, there is virtually nothing about the behavior of our species before prehistoric times to serve as objective data on which to build rational evolutionary explanations. Although a great deal can be gleaned from the behavior of other animals, a field which is known as ethology, mental disorders are far more complex than the behavior of subhuman primates and mammals.

For this reason, I believe that the "end of the beginning" of the Darwinian perspective^[1] on mental disorders should attempt ingenious methods of validation. This report attempts to sketch out a theoretical perspective and some data-based attempts to validate it.

A Theoretical Framework

Bipolar disorders, like anxiety disorders, represent excellent opportunities to conceptualize the link between mental disorders and temperamental attributes. Temperament refers to stable behavior traits with strong affective coloring. Current evidence suggests that bipolarity lies along a continuum from extreme temperament to full-blown affective illness.^[2] Less work has been conducted on the continuum between normal and extreme temperaments,^[3] but whatever data are available do suggest that most temperamental traits are continuously distributed. Although the link between temperament and mental disorder goes back to the earliest days of psychological medicine in the Greek period, it is not presently part of the orthodox body of psychological and psychiatric science.

Nonetheless, many authorities have hypothesized a continuum between cyclothymia and full-blown manic-depressive illness. The German psychiatrist Kretschmer^[4] expressed it most eloquently when he stated that "endogenous psychoses are nothing but exaggerated forms of normal temperament." The British psychiatrist Miller^[5] put it more tersely: "The term manic-depressive psychosis may be correct enough for use in mental hospitals...the term cyclothymia, on the other hand...includes all the milder manifestations, and brings the whole syndrome within the frontiers of everyday life."

Within this theoretical framework, the author submits that affective temperaments play a fundamental role in the predisposition to affective disorder and affective psychoses. Those who oppose this view question why "normal" or "supernormal" traits should underlie a major mental aberration. The question could be more meaningfully examined from the reverse position. I would suggest that the affective temperaments represent the most prevalent phenotypic expression of the genes underlying bipolar disorder: the disorder itself is an aberration^[6] and exists simply because the genes themselves, likely to conform to oligogenic models, are useful for evolutionary ends and, in principle, should be demonstrable in other species. If this model is correct, then adaptive traits must be more common among the "dilute" forms of the illness (ie, bipolar II vs bipolar I), or among the biological "clinically well" relatives who carry some but not all of the genes of the mentally ill proband. Indeed, in a study conducted in collaboration with Kareen Akiskal,^[7] we found that creativity was present in 8% of bipolar II or III vs a negligable rate in bipolar I, schizoaffective, and unipolar depressive patients; the cyclothymic temperament appeared to mediate such creativity. Also, Coryell and colleagues^[8] and Richards and colleagues^[9] demonstrated far greater achievement in the families as opposed to the identified bipolar patients.

An ethological hypothesis can therefore be formulated that would suggest that anxious worrying temperamentally subserves an altruistic role^[10] and that a phobic temperament in fostering dependence would favor the marital bond,^[10] the depressive or melancholic temperament promotes a work orientation,^[11] cyclothymic temperament is involved in exploration and creativity,^[12] and the hyperthymic temperament in territoriality and leadership.^[13]

The Hyperthymic Temperament

An ethological hypothesis can be supported in the most straightforward fashion with the hyperthymic temperament. This temperament is characterized by exuberant, upbeat, overenergetic, and overconfident lifelong traits.^[14] Obviously, such traits have great relevance to territoriality and leadership. Other authors have also described this trait behavioral pattern. For instance, Possl and von Zerssen^[15] describe the biography of these individuals in the following traits: (1) vivid, active, extroverted; (2) verbally aggressive, self assured; (3) strong-willed; (4) self-employed; (5) risk-taking and sensation-seeking; (6) breaking social norms; and (7) generous and spendthrift. This contribution came from a study of the premorbid behavior of bipolar patients. Gardner,^[16] based on a more intuitive formulation, described the behavior of these individuals in even more territorial terms: (1) cheerfulness and joking; (2) irrepressible infectious quality; (3) unusual warmth; (4) expansive; (5) increased self confidence; (6) scheming; (7) robust and tireless; and (8) pushy and meddlesome.

We have developed an operational definition of this temperament and studied in a self-rated form (21 items). In a paper in press,^[17] we have reported emergence of a distinct hyperthymic factor from our analysis of 110 items representing 5 different temperaments. It is noteworthy that aspects most relevant to territoriality and leadership had the highest loadings on this factor, including "I am the kind of person who likes to be the boss" (Table 1).

Table 1. The Hyperthymic Factor

	Factor 4
51. I have a gift for speech, convincing and inspiring the others	0.68
48. I often get many great ideas	0.66
52. I love to tackle new projects, even if risky	0.63
45. I like telling jokes, people tell me I'm humorous	0.58
58. I have abilities and expertise in many fields	0.57
54. I am totally comfortable even with people I hardly know	0.55
55. I love to be with a lot of people	0.53
60. I am the kind of person who likes to be the boss	0.48

The Generalized Anxious Temperament

We have also hypothesized an evolutionary role for a generalized anxious temperament^[10] that represents an exaggerated personality disposition toward worrying. It can be considered an "altruistic anxiety" subserving, hypothetically, the survival of one's extended phenotype in a keen selection paradigm. That worrying would increase upon relaxation is not a paradox, and makes sense in an ethological perspective. It is of great theoretical and practical relevance in our analysis^[17] of the 26 traits that constitute this construct in its self-rated form (among the total of 110 temperament traits) that an independent generalized anxious factor emerged with strong loading on the 3 items related to worrying about one's kin (Table 2).

Table 2. The Generalized Anxious Factor

	Factor 5
99. I am often fearful of someone in my family coming down with a serious disease	0.80
100. I'm always thinking someone might break bad news to me about a family member	0.72
98. When someone is late coming home, I fear they may have had an accident	0.66

The Cyclothymic Temperament

Since our original study^[18] going back to 1977, we have found that "falling in and out of love" was a major characteristic of these individuals. This is obviously of great ethological significance, because ultimately Darwinian evolution works through sexual behavior in transmitting desirable traits. We have hypothesized that the flamboyant and restless pursuit of romantic opportunities in cyclothymia subserves such a mechanism.^[13] Their creative bent in poetry, music, painting, or fashion design, too, may have evolved to subserve such a primordial sexual function.

Further Evidence for the Evolutionary Function of Temperaments

Depressive traits, among other functions, would subserve sensitivity to the suffering of other members of the species, while generalized anxiety temperamentally would subserve altruistic worries; it would not be far fetched to suggest that such traits would enhance kin survival and, by proxy, one's own genome. Cyclothymic traits, with their capriciousness, would make the subject more difficult to attain for lovemaking, thereby assuring that the most robust spouse could be found, who would assure better survival of offspring emerging from such unions. As already stated, hyperthymic traits would lend distinct advantages in exploration, territory, leadership, and mating. These are just some of the possibilities of the rich and complex temperamental traits within an evolutionary framework.

In line with this formulation, new data^[17] from the author's research (Table 3) have shown that both cyclothymic (.35) and hyperthymic (.34) traits are positively and the depressive (-.10) and anxious (-.14) negatively correlated with TCI's novelty seeking. By contrast, harm avoidance is positively correlated with the depressive (.58) and the anxious (.48) -- but interestingly also with the cyclothymic (.49) -- and negatively with the hyperthymic (-.53).The data support the proposed evolutionary functions of the affective temperaments.

Table 3. Correlation Coefficients Between Temperaments and Personality

	Dys	Cyc	Hyp	Irr	Anx
Novelty-seeking	-.10	.35	.34	.26	-.14
Harm-avoidance	.58	.49	-.53	.32	.48

Dys, dysthymic; Cyc, cyclothymic; Hyp, hyperthymic; Irr, irritable; Anx, generalized anxious

Concluding Remarks

These data have important implications for the treatment of mood disorders, particularly the treatment of bipolar disorders. Because dilute expressions of the illness may persist between major episodes, aggressive treatment with mood stabilizers can comprise adaptive functioning and what is unique to the patient as a person. Except in the acute phases of the illness, the emphasis in treatment should be more on functioning than complete mood stabilization.

There are also psychotherapeutic implications.^[19] Generalized anxious temperament can benefit from meditation, a phobic temperament from cognitive behavioral approaches, a dysthymic individual from work as therapy, and the cyclothymic would require rhythmotherapy and limit setting. Hyperthymic individuals are action rather than psychologically oriented, and typically shun psychotherapists and psychiatrists. They are more interested in running the world than "being lectured to" about the desirability of some behavior change at a time of major conflict. The approach to such individuals in psychotherapy is among the most challenging for our field.

References

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2. Akiskal HS. The bipolar spectrum -- the shaping of a new paradigm. Curr Psychiatry Rep. 2002;4:1-3. Abstract
3. Akiskal HS, Placidi GF, Signoretta S, et al. TEMPS-I: delineating the most discriminant traits of cyclothymic, depressive, irritable and hyperthymic temperaments in a nonpatient population. J Affect Disord. 1998;51:7-19. Abstract
4. Kretschmer E. Physique and Character. London: Kegan, Paul, Trench, Trubner and Co. Ltd.; 1936.
5. Miller, Royal Soc Medicine, 1930.
6. Akiskal HS. From dysthymia to the bipolar spectrum: bridging practice and research (Jean Delay Prize paper). Program and abstracts of the XII World Congress of Psychiatry; August 24-29, 2002; Yokohama, Japan.
7. Akiskal HS, Akiskal K. Re-assessing the prevalence of bipolar disorders: clinical significance and artistic creativity. Psychiatrie et Psychobiologie. 1988;3:29s-36s.
8. Coryell W, Endicott J, Keller M. Bipolar affective disorder and high achievement: a familial association. Am J Psychiatry. 1989;146:983-988. Abstract
9. Richards R, Kinney DK, Lunde I, Benet M, Merzel AP. Creativity in manic-depressives, cyclothymes, their normal relatives, and control subjects. J Abnorm Psychol. 1988;97:281-288. Abstract
10. Akiskal HS. Toward a definition of generalized anxiety disorder as an anxious temperament type. Acta Psychiatr Scand. 1998;98(suppl 393):66-73.
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12. Akiskal HS, Rosenthal RH, Rosenthal TL, Kashgarian M, Khani MK, Puzantian VR. Differentiation of primary affective illness from situational, symptomatic, and secondary depressions. Arch Gen Psychiatry. 1979;36:635-643. Abstract
13. Akiskal HS. Dysthymia, cyclothymia and related chronic subthreshold mood disorders. In: Gelder M, Lopez-Ibor J, Andreasen N, eds. New Oxford Textbook of Psychiatry. London: Oxford University Press; 2000:736-749.
14. Akiskal HS. Delineating irritable-choleric and hyperthymic temperaments as variants of cyclothymia. J Person Disord. 1992;6:326-342.
15. Possl J, von Zerssen D. A case history analysis of the 'manic type' and the 'melancholic type' of premorbid personality in affectively ill patients. Eur Arch Psychiatry Neurol Sci. 1990;23:347-355.
16. Gardner R Jr. Mechanisms in manic-depressive disorder: an evolutionary model. Arch Gen Psychiatry. 1982;39:1436-1441. Abstract
17. Akiskal HS, Mendlowicz MV, Girardin J-L, et al. Validation of a scale designed to measure variations in temperament. J Affect Disord. 2003; In press.
18. Akiskal HS, Djenderedjian AH, Rosenthal RH, Khani MK. Cyclothymic disorder: validating criteria for inclusion in the bipolar affective group. Am J Psychiatry. 1977;134:1227-1233. Abstract
19. Akiskal HS. Psychopharmacologic and psychotherapeutic strategies in intermittent and chronic affective conditions. In: Montgomery S, Rouillon P, eds. Long-Term Treatment of Depression. London: J. Wiley & Sons; 1992:245-263.