Heredifas 66: 177-182 (1970)

Genetic association of giftedness and creativity with schizophrenia JON LOVE KARLSSON National Archives, Reykjavik, Iceland

(Received September 14, 1970)

This comparative study of Icelanders, born during the period 1881-1910, indicates that close relatives of psychotic individuals have a significantly increased probability of being considered persons of eminence. Their rate of listing in Who Is Who is doubled, both in regard to general listings and those based on artistic or scholastic endeavors. Review of relevant literature supports the view that the dominant principal gene proposed for schizo- phrenia may in a heterozygous state lead to cerebral stimulation, with improved performance in areas of giftedness and creativity.

While authorities in the behavioral fields have often been inclined to discount the importance of hereditary factors in personality development, geneticists have generally recognized that children are born with varying mental potentials. Longi- tudinal studies have supported the existence of behavioral differences in infants which persist during subsequent growth (THOMAS et al. 1968). Studies of monozygotic twins reared apart have indicated that the personality traits of each pair tend to rsmain alike despite early separation (NEWMAS et al. 1937; SHIELDS 1962; JUEL- NIELSEN 1965). Correlation studies of intelligence tests have also shown that no other relatives, although reared together, come close to attaining as similar scores as monozygotic twins, even if they are reared apart (ERLENMEYER-KIMLING and JARVIK 1963). However, specific genetic studies in this area have been assumed to be rather im- practical, as one would guess that many factors are involved and that the total picture is quite complex.

Recent studies of the family transmission of schizophrenia have led to the conclusion that genetic factors are of principal importance in that disorder. The elevated risk of psychosis in close relatives of schizophrenic index cases appears to remain unchanged even if they are reared away from their biologic families (HESTON 1966; ROSENTHAL et al. 1968; KARLSSON 1970 a). The

majority of geneticists interested in this field agree that the most likely basic mode of transmission for schizophrenia is dominant inheritance (BOOK 1953; HUXLEY et al. 1965; KARLSSON 1966), although additional modifying factors must be postulated to account for the total family pattern of psychosis. The present author has previously favored a two locus mechanism based on a dominant principal gene and a recessive secondary gene, but new data gathered in Iceland do not support this hypothesis, but rather suggest a system requiring two separate dominant genes (KARLSSON 1970 b). In this latter system the less frequent of the two genes, being the one whose presence or absence is easier to demonstrate, is considered to be the principal gene.

These developments have paved the way to- ward a more specific study of genetic factors involved in the development of basic personality traits. Individuals can be identified who are likely to carry only the principal gene of schizophrenia, and while such persons do not develop psychosis, there are indications that their personalities differ from those of non-carriers (KARLSSON 1968). It has been proposed that the gene in question may be involved in the physiologic regulation of the arousal system of the brain, thus helping to explain how simple genetic variations can lead to profound personality differences.

The present paper presents additional evidence

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178 J ~ N LOVE KARLSSON

in support of the view that carriers of the pro- posed principal gene of schizophrenia tend to be relatively gifted or creative.

Methods and results This investigation is based on the population of Iceland, a country particularly well suited to quantitative genetic studies of commonly occur- ring conditions. The total population of 2OO,OOO, the geographic stability, the high cultural level, the excellent records, and the high medical stand- ards are some of the favorable factors.

Persons born between 1881 and 1910 were chosen for a comparative study of giftedness. The control group consisted of 3793 persons born during this interval, surviving and available after age 15 years. These individuals were selected from three large books on genealogy published by different authors and covering all regions of Ice- land (JONSSON 1932; ZOPHONIASSON 1939; GISLASON and VALDIMARSSON 1959). Of these persons 1959 were males. To establish a basic index of giftedness the rate of listing in Who Is Who in Iceland was ascertained by the use of two indices, published two decades apart (TOBIASSON 1944; GUDNASON and HARALDSSON 1965). Almost one-tenth of all males was found to be listed in at least one of these books.

Psychotic persons, identified from the records of the Kleppur Mental Hospital in Reykjavik, were divided into three generations, those born in theintervals 1851-1880,1881-1910, and 1911- 1940. The study was limited to those index cases on whom family information was available, the majority being listed in the same genealogy books from which the control group had been selected. The 1851-1880 index cases served as a source of sons and nephews, the 1881-1910 index group provided brothers, and the 1911- 1940 index cases were used to identify fathers and uncles, all study cases being born in the interval

Each group thus identified was studied for the rate of listing in Who Is Who. The results are shown in Table 1 , giving separately relatives of index cases diagnosed schizophrenic and manic depressive. In the last column both groups are combined, as there is considerable evidence that the major psychoses are closely related genetically (KARLSSON 1971). It will be noted that the rate of listing is considerably higher for the relatives of psychotic persons than for the control group.

Although the available material is rather limit- ed for a separate study of creative persons, a group was segregated which included only those listed in Who Is Who on the basis of creative endeavors rather than because of social position, which is the most common reason for inclusion in such books. These data, which also are restrict-

1881-1910.

Table 1. Rate of listing in Who Is Who in Iceland of males born in the interval 1881-1910, related as indicated to psychotic index cases

Study group Fraction listed according Total Per cent to diagnosis of index case number rate of

Schizo- Manic phrenic depressive

studied listing

General population 1959 Kindred 1 698 Kindred 2 722 Kindred 3 539 First degree relatives 281213 16/69 282 Fathers 13/85 4/16 101 Brothers 1411 12 613 1 143

Uncles 10169 6/24 93 Nephews 17/80 713 1 1 1 1

Sons 1/16 6/22 38 Second degree relatives 271149 13/55 204

Deviation from general population rate significant, p < 0.01

9.2 10.7 6.5

10.9 15.6 16.8 14.0 18.4 19.6* 17.2 21.6

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GIFTEDNESS AND SCHIZOPHRENIA 179

Table 2. Listings in Who Is Who for creativity among randomly selected Icelandic males and among first and second degree male relatives of psychotic patients, all born in the interval 1881-1910

Description of group General population Relatives of psychotic propositi

Kindred 1 Kindred 2 Kindred 3 Schizo- Manic phrenic depressive

Total males studied Number listed in Who Is Who Creative persons listed in Who Is Who

Scholars Novelists Poets Painters Composers Performers

Fraction listed for creativitv

698 722 75 47 7 3 2 3 I 0 0 0 3 0 I 0 0 0

13/1959 =0.7%,*

539 59

3 2 1 0 0 0 0

362 124 55 29 5 6 2 1 1 0 1 0 1 1 0 2 0 2

11/486=2.3%*

* Difference significant at 0.001 level

Table 3. Comparison of the per cent incidence of psychosis and of giftedness for each generation in the different branches of Kindred 1 The numbers in parentheses are based on either one or two cases, and blanks indicate that no psychosis or giftedness is recorded

Gene- Branch A Branch B Branch C Branch D Branch E Branch F ra- N = 1 4 8 8 N =648 N = 1141 N = 807 N = I64 N =278 tion

Schizo- Gifted- Schizo- Gifted- Schizo- Gifted- Schizo- Gifted- Schizo- Gifted- Schizo- Gifted- phrenia ness phrenia ness phrenia ness phrenia ness phrenia ness phrenia ness

- - - - - - .... ~~ 11 (12.5) (25.0) - - Ill (4.8) (4.8) - - - (10.0) --

V 4.7 2.3 (1.2) 7.2 ( 1 . 1 ) 3.2 (1.1) - - __

~ - . - (4.2) - ~~ (4.8) IV (2.1) 8 .3 ~ 11.6 - ~ - - (2.6) (2.5) - (2.8)

VI 3.6 7.5 2.4 5.4 (0.4) 1.9 2.8 3.3 - (1.5) 6.0 VII 1.7 5.6 1.7 4.8 0.7 2.4 (0.5) 2.3 (1.0) 4.0 (1.4) 4.1

- -. -

Aver- age* 2.6 6.0 1.7 5.6 0.5 2.1 1.6 2.2 (0.6) 2.4 1 . 1 4.3

* Overall rates for the kindred are 1.6 per cent recorded psychosis and 4.0 per cent listings in Who Is Who.

ed to males born in the period 1881-1910, are summarized in Table 2. Again there is a higher rate of listing for relatives of psychotic patients. The numbers are too small to permit a separate study of just the closest relatives, but it may be of interest that seven of the eleven creative relatives of psychotic patients are first degree relatives.

To demonstrate that the increased rate of listing in Who Is Who is specifically associated with the dominant principal gene postulated for

schizophrenia, the rate of psychosis and the rate of giftedness were compared in the different branches of the one of the three kindreds which is known to have an uneven distribution of psy- chosis (KARLSSON 1971). The data in Table 3 indicate that the same branches are high in both psychosis and listings in Who Is Who. Particularly striking is the differ:nce between branch A and branch C, both of which are quite large. Branch A has produced many psychotic as well as many

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180 J ~ N LOVE KARLSSON

gifted persons, while branch C has little psychosis and is almost devoid of giftedness as measured by listings in Who Is Who. In previous studies it has been concluded that the principal gene of schizo- phrenia has been present in branch A from the start, while branch C probably was free of this gene for several generations (KARLSSON 1964).

Discussion On the basis of preliminary data it was proposed several years ago (KARLSSON 1966) that the mentality of relatives of psychotic patients might be favorably influenced by some of the genes involved in schizophrenia. In his study of foster reared children of schizophrenic mothers HESTON (1966) also observed that they tended to exhibit more colorful personalities than a control group born to non-psychotic mothers.

In another study of the family designated here as Kindred 1, whose genealogy is well documented since the birth of the original ancestors in 1682 (JONSSON 1932), it has been demonstrated that all the highly gifted persons identifiable among the descendants born before 1880 had close rela- tives who were psychotic (KARLSSON 1968). While the rate of recorded psychosis for the entire kindred was 1.6 per cent, the relatives of the most gifted members had a rate almost three times that high or 4.5 per cent. The term super- phrenic was suggested to denote carriers of the proposed principal gene, while those carrying the modifying gene were designated tensiphrenic and those carrying neither norrnophrenic. Those possessing both abnormal genes were considered to have a schizophrenic constitution, such indi- viduals at times manifesting a high degree of creativity in addition to their risk of psychosis.

The results of the present study are in agree- ment with the previous data and suggest that some type of mental stimulation is associated with a genetic relationship to psychotic persons. The probability of being listed in Who Is Who seems to be doubled for close relatives of psychotic individuals. The somewhat higher rate of listing for second degree as compared to first degree relatives may be explained by the fact that the closest relatives of psychotics are the ones most prone to suffer from severe emotional problems, presumbably being the ones most likely to receive

the responsible genes in potentially harmful combinations.

It appears likely that the group referred to in the present study as superphrenics may corre- spond to persons whom MCCONAGHY and CLANCY (1968) have called allusive thinkers on the basis of performance on object sorting psycho- logic tests. Since the test responses of such persons are similar to those seen in schizophrenic patients, MCCONAGHY (1 959) originally considered this type of response to constitute a thought dis- order, but later results have suggested that a different designation may be more appropriate. Allusive thinking was felt to be deviant in that such persons allude to the correct answer rather than responding more directly as normals do. Even in MCCONAGHY and CLANCYS data it is apparent that allusive thinkers can be good scholars. They are also found more often among relatives of schizophrenics, in fact in the original report MCCONAGHY felt that he could identify at least one parent of each schizophrenic as thought disordered.

Recent neurophysiologic studies may also support a relationship between schizophrenia and giftedness. Several authors have described exces- sive physiologic responsiveness to external stimuli by schizophrenics and their relatives (ZAHN 1964; MEDNICK and SCHULSINGER 1968). Persons with a high intelligence quotient on psychometric tests exhibit similar overresponsiveness as measured by evoked potentials in the electroencephalogram (ERTL and SCHAFER 1969).

Several investigators have presented data in the past which suggest a relationship between intelli- gence and mental illness. MYERSON and BOYLE (1941) surveyed eminent American families and reported an increase in psychosis, especially manic depressive illness. JUDA (1949), attempting to disprove that men of genius were often psycho- tic, found a significant increase in mental illness and suicide in all close relatives of the index cases, most of whom would probably be classified as gifted rather than highly creative. TERMAN and ODEN (1959), in a longitudinal study of gifted persons, encountered a high rate of suicide by age 40 years, although recognized psychosis may not have been increased.

Like their relatives, highly creative persons have also been reported to have an increased rate of psychosis. In a very thorough world wide survey of men of creative genius LANGE-EICHBAUM (1 928)

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GIFTEDNESS AND SCHIZOPHRENIA 181

found a history of psychosis in over 40 per cent of the greatest contributors to human endeavors. Other investigators have reported that creative persons show responses on projective psychologic tests which closely resemble those observed with psychotic patients (MACKINNON 1962; BARRON 1963; DUDEK 1970).

All these studies are consistent with the hypo- thesis that psychosis may be related to an inherit- ed tendency to overproduce stimulant neuro- hormones which also have a function in intellec- tual processes. These effects are assumed to be related to a heterozygous state with respect to the principal gene of schizophrenia. Extension of the present research to include a larger number of individuals is in progress.

Acknowledgements. ~ The author is grateful to Professor Tomas Helgason for making available records from the Kleppur Mental Hospital in Reykjavik and to Professor Gudni Jonsson for supplying specific information about one of the kindreds involved in this study.

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12 Hereditas 66, 1970