Serum uric acid, serum cholesterol and personality

JournalofPsychosomolrc Printed in Great Britain.

Research, Vol. 26, No. 3, pp. 291-299, 1982.

SERUM

URIC ACID,

0022.3999/82/030291-09%03.W/O Pergamon Press Ltd.

SERUM CHOLESTEROL

AND PERSONALITY* M.

K.

RAINAt

and

ARUNIMA

VATS?

(Received 23 June 1981;accepted in revised form 19 October 1981) Abstract-This study investigated the relationship between serum uric acid concentrations, serum cholesterol and personality scores of the undergraduate students of Punjab University, Chandigarh, India. Two groups (Group A and Group B) of subjects were carefully selected on the basis of various criteria. They donated 5 ml of blood which was analyzed for uric acid and cholesterol concentrations. The Maudsley Personality Inventory was used to assess personality traits. Subject’s extraversion scores were found to be related with their uric acid concentrations in Group B and in the Combined Group, even after controlling for the effect of cholesterol. Results have been discussed in terms of the nature of the biochemical variables involved. Further experimental research, involving subjects from different backgrounds, using different measures of personality, motivation and performance is suggested.

INTRODUCTION THE behaviours of which man is capable are related to internal biochemical and electrical events. Since personality types are essentially based on constitutional, genetic or in-born factors, which are to be discovered in the physiological, neurological and biochemical structures of the individual, Nunnally [l] considers that it is reasonable to hypothesize that some personality traits relate to some of the myriad chemical components of the bloodstream. In fact, the whole endocrine system and one’s distinctive brain morphology form the basis for determining personality [2]. This has the support of Eysenck [3], who after extensive studies on extraversionintroversion and neuroticism (the two basic dimensions of personality) maintained that we would postulate E(extraversion) and N(neuroticism) as causal influences in behaviour not because they emerge so repeatedly and strongly from factorial studies [4] but because of the psychological theories and arguments related to findings in learning theory, genetics, physiology, biochemistry, perception, anatomy, psychopharmacology and many other disciplines [5]. It, therefore, is essential that there should be a constant search for those biological events that explain human variations, individuality and personality. Serum uric acid (SUA) is one of the biochemical factors which has received considerable attention during the past few years and has been found to be associated with variables such as intelligence, cognitive style, achievement behaviour, drive and socio-economic status. A variety of indicators-grades [6-81, test performance, extra-curricular activities, achievement motivation [9-l 11, need for exhibition [ 121, occupational differences [13] have been found to be related with high serum uric acid levels. Biochemically, various hypotheses have been advanced to interpret these associations. However, most of the workers in this area have interpreted these associations in terms of Orowan’s [14] hypothesis which suggested that because of the similarity in molecular structure with purines, caffein, theobromine and ALL

*This investigation was supported by grants from the Educational Research of the National Council of Educational Research and Training, New Delhi. $-National Institute of Education, New Delhi-l 10016, India. 291

and Innovation

Committee

292

M. K. RAINA and ARUNIMA VATS

theophylline, uric acid may work as a central nervous system stimulant and that its association with behaviour is via its role as cortical stimulant [15]. Recent studies [16, 171 have shown that uric acid may be relevant and a promising biochemical substance, which can be studied in relation to some aspects of personality and certain human behaviour. Studies using SUA can also provide evidence whether there is any validity in Eysenck’s [3] theoretical stand in associating uric acid with personality as viewed by him. It is because of these reasons that serum uric acid has been included in this study as one of the biochemical variables. Serum cholesterol is another biochemical variable which is of importance in relation to human needs, thoughts and behaviour. The interest has stemmed from the fact that elevated serum cholesterol is one of the risk factors for coronary heart disease. Serum cholesterol has been seen to increase under psychologically stressful conditions in a number of studies and has also been found to rise significantly in human life situations associated with anxiety. Life situations where serum cholesterol was documented to be appreciably high were those of tax accountants [18], in Navy Underwater Demolition Team during there motivation week of training [19] and in medical students before they appeared for their final examination [20, 211. The work of Rosenman and Friedman [22, 231 and Jenkins et al. [24] suggest that a certain overt emotional complex termed behaviour pattern Type A, and composed primarily of an enhanced competitiveness, drive, aggressiveness and hostility, an exessive sense of time urgency and motor signs of impatience and restlessness, is associated with elevated cholesterol levels and increased prevalence of coronary heart disease. In agreement with this work are the findings of Sloane et al. [25] and Payne et al. 1261. They found sizeable correlations between cholesterol levels and independent psychiatrists’ ratings of subjects’ need for social achievement, ambition, autonomy, aggression and physical and verbal hostility. Self-ratings of dissatisfaction with one’s ambition and an objective measure of persistence on an intellectual task were also strongly related to blood cholesterol levels measured when the subjects were in the fasting state. Flemenbaum and Anderson [27] found positive association between field-dependence and serum cholesterol levels in case of female psychiatric patients and the description of field-dependents is similar to what Friedman and Rosenman term Type A personality. However, no significant association was found between field-dependence and blood cholesterol in male psychiatric patients. AS far as serum cholesterol and its association with other behavioural indices is concerned, very few studies have been done on the normal healthy individuals, especially students. This was the reason to include serum cholesterol as another biochemical variable to be studied in relation to personality. Moreover, a pertinent biochemical reason in taking cholesterol levels into consideration was that it could sharpen the association between SUA levels and other behavioural indices [28, 291. METHODS

Subjects. In order to study the normal individuals, who have the maximal range of responses [7] students from the undergraduate classes of the Punjab University were contacted. For the present investigation, 190 male undergraduate students (94 from technical and 96 from professional course) volunteered to participate. A number of checks, as reported in literature [30], were made to ensure that confounding variables were controlled so as to eliminate any subject who failed to meet certain criteria of acceptability for the study. It was checked that the subjects were healthy, free of fever and exposure to cold. Range of body temperature was normal (98.3-98.7”F). They showed a normal variation in

Serum uric acid, serum cholesterol

and personality

293

terms of height and weight. They were free of the effects of soft drugs, excessive use of aspirin-type drugs, and of caffeine- and alcohol-containing beverages during the 24 h prior to testing. They did not participate in strenuous exercises, and no dietory changes had been made during the four weeks prior to testing. Following these criteria a total of 150 subjects-72 students (Group A) from technical and 78 students (Group B) from professional courses-actually participated in this study. Each subject donated 5 ml of intravenous blood in the morning, and after separating serum from blood, it was analysed for uric acid and cholesterol concentrations. Determination of serum uric acid and serum cholesterol. For estimating serum uric acid concentrations and serum cholesterol, phosphotungstate and calorimetric methods were used respectively [31]. Test retest reliability coefficients of estimating uric acid and cholesterol after a period of 9 months on repeated venepunctures were found to be 0.62 and 0.87 respectively. Eysenck’s Maudsley Personality Inventory. The Maudsley Personality Inventory (MPI) was used for assessing neuroticism-stability and extraversionintroversion dimensions of personality. In the present investigation Hindi version of MPI by Jalota and Kapoor [32] was used. Studies [33-351 suggest that this Indian version of the MPI gives results not essentially different from those obtained with original version in England and it seems reasonable to conclude that these personality dimensions can be found among Indian students as well as among various European and American groups [5] on whom the test has been standardized.

RESULTS

Table I presents the mean serum uric acid, serum cholesterol concentrations and mean extraversion and neuroticism scores for Group A, Group B and the Combined Group respectively. TABLE

I.-MEANS

AND

STANDARD

DEVIATIONS

OF SERUM

Group Mean

A

Variable Serum uric acid Serum cholesterol Extraversion Neuroticism

4.48 176.04 28.04 18.19

0.57 18.00 6.77 10.28

S.D.

URIC

A,B

EXTRAVERSloNANDNEUROTICISMSc"RESFORGRoUP

ACID,

SERUM

CHOLESTEROL,

ANDCOMBINEDGROUP

Group Mean

B

4.79 204.42 28.42 16.21

0.58 20.10 6.65 10.93

S.D.

Combined Mean

Group

4.64 189.62 28.23 17.16

0.60 20.17 6.70 10.62

S.D.

The mean SUA levels in both the groups and the Combined Group fall within the normal range. Earlier studies on uric acid have shown similar mean serum uric acid concentrations for normal individuals in Indian [36, 371. For serum cholesterol, the comparative data are not easily available on normal individuals. Conventionally, the normal cholesterol levels are considered to fall between 120 and 230 mg per cent and the means presented in Table I lie within this range. As for the mean extraversion and neuroticism scores, earlier studies [38, 391 have reported almost similar means. The earlier evidence [7] indicates that relationship between uric acid levels and some behavioural variables appears to vary, depending perhaps upon the school setting (and also, no doubt, on unknown factors in the selection of subjects for study). Therefore, the analysis of the data was done separately for the two groups. However, results are also being reported for the Combined Group following Eysenck’s [40] suggestion. Two-way analysis of variance technique was adopted to determine to what extent the personality types, as measured by MPI, differ in serum uric acid concentrations. Subjects in both the groups as well as in the Combined Group were divided following Savages’ [41] classification into four equal groups according to extraversion and neuroticism scores. Using the notation that E stands for high extraversion, e stands for low extraversion, N for high neuroticism and n for low

294

M. K. RAINA and ARUNIMAVATS

neuroticism, the groups were (a) EN, (b) eN, (c) En, (d) en. Subjects in Group A with extraversion score 30 and above, in Group B with 28 and above and in the Combined Group with 31 and above were rated as E and those with scores below 30 in Group A, 28 in Group B and 3 1 in the Combined Group as e. High neuroticism score N had a cut-off point 17 in Group A, 16 in Group B and 18 in the Combined Group and those below being in n category. The results are presented in Table II for Group A, Group B and the Combined Group respectively. The results in Table II for Group A show that there is no significant association between subjects’ scores on extraversion and neuroticism with SUA levels. The interactional effects are also not significant. The results for Group B and the Combined Group indicate that there is a significant association between SUA levels and subjects’ scores on extraversion. The F value is significant at 0.05 level. The extraversion-neuroticism effects remain insignificant in these groups also. A similar analysis was made for the three groups by taking their serum cholesterol levels into consideration; see Table III. Again, no significant association has been found between serum cholesterol concentrations and subjects’ scores on MPI. However, for Group A the interactional effects are high (though not significant) as compared to Group B, where the interactional effects are quite low. Correlation coefficients were worked out between the subjects’ scores on E and N as measured by MPI and their SUA and serum cholesterol concentrations separately. The coefficients for Groups A, B and the Combined Group are entered in Table IV. Table IV indicates that none of the dimensions of personality are significantly related with either serum uric acid or serum cholesterol. However, following Eysenck’s suggestion that corrections for attenuation [42] may be applied, it was found that in case of Group B and the Combined Group the correlation between uric acid and extraversion became significant indicating that under the conditions of this study extraversion seems to be significantly related to the uric acid levels. Cholesterol surprisingly has shown significant, though, negative association with neuroticism. It has been pointed out earlier that if serum cholesterol is taken into consideration it may sharpen the association between SUA and other behavioural indices. Hence the subjects in Groups A, B and the Combined Group were divided into high cholesterol and low cholesterol groups on the basis of their mean cholesterol levels. Tetrachoric correlations were computed between uric acid and personality dimensions (appropriate because of artificially dichotomous variables). The results are presented in Table V and VI. These results indicate that in Group A there is no association between uric acid and any of the personality dimensions. However, in Group B and the Combined Group, uric acid has shown significant relationship with extraversion. It is only in Group B that uric acid has been found to be associated with neuroticism in low cholesterol group. It may be mentioned here that in both Group B and the Combined Group, SUA and cholesterol levels are higher in comparison to the Group A. DISCUSSION

Earlier investigations [lo, 12, 26, 43-451 on the association of SUA and serum cholesterol with personality traits have reported different results with different

Extraversion (E) Neuroticism (N) ExN Within sets

Source

*P = 0.05.

Extraversion (E) Neuroticism (N) ExN Within sets

Source

1152.00 32.00 1844.10 26523.00

ss

0.002 0.010 28.830

0.046

SS

1 1 1 68

0.08 0.51

2.43

F

1152.00 32.00 1844.10 390.00

2.95 0.08 3.04

F

TABLE III.-ANALYSIS

0.002 0.010 0.019

Group A MS

df

1 1 I 68

0.046

Group A MS

df 1 1 1 74

0.098 0.001 0.012 0.017

0.05 0.71

5.11;

F

82.95 0.32 50.95 12052.67

ss 1 1 1 74

df

Group

82.95 0.32 50.95 162.87

B MS

1.62 0.0 0.31

F

OF VARIANCEOF SERUMCHOLESTEROLLEVELS

0.001 0.012 24.350

Group B MS

df

OF VARIANCEOF SUA LEVELS

0.098

ss

TABLE II.-ANALYSIS

5280.57 1104.57 4868.67 420830.87

ss

0.03 0.04 71.18

2.82

ss

1 1 1 146

df

Combined

1 1 1 146

df

Combined

5280.57 1104.57 4868.67 2882.40

Group MS

0.03 0.04 0.48

2.86

Group MS

1.83 0.38 1.68

F

0.06 0.08

5.87*

F

M.K.

296

RAINA and ARUNIMAVATS

TABLE IV.-CORRELATION COEFFICIENTSOF SUA AND SERUM CHOLESTEROL WlTHPERSONALlTYSCORESFORGROUP A,B ANDCOMBINEDGROUP

Traits Extraversion Neuroticism Extraversion Neuroticism

SUA

\A IB

0.06 0.04 0.15 0.01 0.11 0.04

Corrected 0.12 0.06 0.30* 0.01 0.22* 0.06

Serum cholesterol

-0.07 -0.20 -0.04 -0.04 0.00 -0.18

Corrected -0.11 0.32* ~0.06 -0.05 0.00 0.29

*P = 0.05.

subjects using different measures. In some studies the results obtained showed that the association between these variables was quite strong and in others it was insignificant. The results obtained in the present investigation show that extraversion as measured by MPI is moderately though significantly associated with SUA. However, results relating to cholesterol are not clear and conclusive. Earlier studies have also shown that extraverted qualities, like drive, leadership, pushing of self, range of activities, exhibitionism, etc. are associated with uric acid. Most of the above mentioned studies have used tailor-made questionnaires for a particular group of subjects except for one study [26] in which MPI was used with the university students and the correlation coefficients obtained between serum cholesterol concentrations and the subjects’ scores on MPI were insignificant. The possible explanation suggested for such results was that neurotic behaviour while it cannot be identified with anxiety can be conceived of as a reaction to it. Some neurotic behaviour can be explained as serving to reduce the level of anxiety. It has been argued that high cholesterol subjects, while having high basic drive level are nevertheless not neurotic in any usual sense of the term, because their method of reducing their anxiety is non-neurotic. That is, they reduce their anxiety, by socially acceptable competitive behaviour. Therefore, they would not display an unusually high degree of ‘neuroticism’ as measured by a questionnaire and hence no significant association is obtained. Moreover, it is very difficult to explain such results as SUA and serum cholesterol are quantitative variables and personality characteristics and other human behaviours are qualitative phenomena. The issues involved in suggesting whether man’s biochemical variables affect his personality style or his personality pattern has influence on biochemical factors cannot be settled at the moment because of the profound complexity of the problem in this interdisciplinary area of research. Again, the functions of SUA and serum cholesterol are not very clear and need further investigations. As these issues at the molecular level get clarified, our thinking about the associations between biochemicals and behaviour, observed at the molar level, may have to be modified [29]. Perhaps the relationship between serum uric acid and psychological variables is not exactly linear [46], though it may be having an indirect influence on such behaviours via learning. Cultural variations in socialization experiences may also affect these associations. Besides, SUA and serum cholesterol get influenced by a host of other factors. However, there is a need to examine evidence which comes from more specific investigations, with larger samples, using different measures

High 9 11

Low 12 I

Low 13 6

High 8 I2

Low 10 9

High I1 5

Low I 10

Group A Low cholesterol* High cholesteroljSUA SUA

*Tetrachoric r = 0.00. j-Tetrachoric r = 0.07. q?.Tetrachoric r = 0.39, P = 0.05. PTetrachoric r = 0.04.

Extraversion Low High

High 9 5

High 6 10

Low 9 6

High 8 14

Low 15 10

Group B Low cholesterol* High cholesterols SUA SUA High I6 22

Low 18 12

Combined Low cholesterolj[ SUA

LEVELSAND EXTRAVERSIONSCORES

High 7 9

Low 6 9

High 4 19

Low 9 15

Group B Low cholesterol* High cholesterolzjz SUA SUA

High 18 20

Low 15 15

Combined Low cholesterol@ SUA

TABLE VI. INFLUENCE OF CHOLESTEROL ON ASSOCIATIONBETWEENSUA LEVELSAND NEUROTICISMSCORES

*Tetrachoric r = 0.28. -fTetrachoric r = 0.07. $Tetrachoric r = 0.35, P = 0.05. 5 Tetrachoric r = 0.36, P = 0.05. IlTetrachoric r = 0.30, P = 0.05. 1ITetrachoric r = 0.16.

Extraversion Low High

Group A Low cholesterol* High cholesterol? SUA SUA

TABLE V.--INFLUENCE OF CHOLESTEROL ON ASSOCIATIONBETWEENWA

Low 24 17

High 20 20

Low 20 22

Group High cholesterol* SUA

High 20 21

Group High cholesterol SUA

(1

298

M. K. RAINA and ARUNIMA VATS

of personality and subjects from different institutions. At present the methodological issues involving psychological and physiological measurements are also involved, limiting the generality of the findings. Acknowledgements-We reading of the manuscript

are indebted to Professors H. J. Eysenck and R. G. Misra and provision of advice and constructive criticism.

for their critical

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