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SEASONALITY IN SCHIZOPHRENIA

SiR,--The curious and persistent finding that schizo-phrenics are more likely to be born in the months of Januaryto May, discussed in your editorial of March 4, admits of afurther explanation.

Rather than a winter birth being associated with factorsthat could cause schizophrenia (such as infection or malnu-trition) it could be that the fertility of the parents carrying theschizophrenia genotype varies more than normal during theyear. If one was to take the hypothesis (which I have discussedelsewhere’) that schizophrenia is part of an adaptation to iso-lated conditions, one would expect that such a populationwould need to exert close control over the time of birth. Birthin early spring would be well adjusted to survival because theperiod of intensive nursing care would be over before foodgathering took place. Larger colonies, however, would benefitfrom births being spread throughout the year, since this wouldprevent too many of the colony being incapacitated by preg-nancy and early infancy at one time, the impact of one or twomothers opting out of food gathering being less on such a largecolony.A simple test to distinguish whether the timing of births of

schizophrenics is due to genetic factors in the parents ratherthan environmental insults to their offspring would be to com-pare the birth dates of schizophrenics with those of their sib-lings. If these showed the same deviations from normal thedeviation would presumably be due to differential fertility inthe parents, and possibly support the above hypothesis. If thebirth dates of siblings conformed to the normal pattern, thiswould support the environmental hypothesis.Department of Psychiatry,St George’s Hospital Medical School,London SW17 J. KELLETT

SiR,-In discussing explanations for seasonality in schizo-phrenic births you dismiss the possibility that parents of

schizophrenics differ from the general population in their pro-creative behaviour. However, there is good evidence that theydo: Hare2 reported that the season of birth of schizophrenicpropositi is similar to that of their normal sibs.

There is some degree of genetic determination in schizo-phrenia : schizophrenic propositi are more likely to have schi-zoid parents. My suggestion is that in the summer, people wearfewer clothes in bed, and that a schizoid spouse is more likelythen to notice his (or her) co-spouse there and accordingly toinitiate sexual behaviour. This suggestion is strengthened bythe finding’ that in the U.S., the amplitude of seasonality inschizophrenic births is less in the South than in New Englandand the Mid-West (where the seasonal variation in tempera-ture is greater).Galton Laboratory,Department of Human Genetics and Biometry,University College London,London NW1 2HE WILLIAM H. JAMES

SiR,—Investigations of season of birth in schizophrenia andseasonal variations in vitamin-D metabolism suggest a role forneonatal vitamin-D deficiency in schizophrenia.

In northern latitudes schizophrenia tends to be associatedwith winter and early spring births. Explanations of this find-ing range from social and biological selection to nutrition andinfection and include factors influencing conception, delivery,and the neonatal period.Few factors can be identified which would operate con-

1. Kellett, J. Lancet, 1973, i, 860.2. Hare, E. H. Br.J. Psychiat. 1976, 129, 49.3. Torrey, E. F., Torrey, B. B., Petersen, M. R. Archs gen. Psychiat. 1977, 34,

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sistently across diverse cultures and geographic locations. Per-haps the most striking is the variation in exposure to ultra-violet light with seasonal change. The most obvious biologicaleffect of ultraviolet exposure is the conversion of 7-dehydrocho-lesterol to cholecalciferol (vitamin D) which is 25-hydroxylatedin the liver to the major circulating metabolite of vitamin Din man.A pronounced seasonal variation in serum-25-OHD has

been demonstrated from infancy to old age, in both sexes, andin many races, with higher concentrations in summer than inwinter.

Hillman and Haddad’ measured seasonal variations in ser-um-OHD in women in the third trimester of pregnancy. Augustlevels were almost three times higher than February ones. Norelation was found between season and maternal calcium.They further demonstrated a pronounced correlation betweenmaternal and cord serum 25-OHD at birth.2 Roberts et al.3found an increased incidence of neonatal hypocalcaeInic con-vulsions among infants born in late winter or early spring.The greater perinatal risk of vitamin-D deficiency and hypo-

calcaemia in winter months could be responsible for the in-creased risk of schizophrenia. Several mechanisms might oper-ate. Hypocalcaemia or vitamin D deficiency itself mightpermanently affect the developing nervous system. Maternalvitamin-D deficiency might affect complication-rates at deli-very. Most intriguing, however, is the possible effect of hypo-calcaemia upon the psychological development of the newborn.

Calcium is an important factor in the regulation of neuraland neuromuscular transmission. In the adult, moreover,

hypocalcaemia is accompanied by neuromuscular excitability,emotional irritability, and sometimes psychosis. The hypo-calcxmic neonate might therefore experience significant altera-tions both in perception and motor function. A major distor-tion of experience during this critical phase of

perceptual-motor development might lay the foundation forlater psychopathology.

Perinatal vitamin-D deficiency may therefore be a risk fac-tor for subsequent development of schizophrenia. Vitamin-Ddeficiency in the neonate may often result from reduced mater-nal exposure to ultraviolet light, accounting for the associationof schizophrenia with winter birth.The most direct test of this hypothesis for a role of calcium

would be to follow up a cohort of hypocalcaemic neonates andcompare the incidence of schizophrenia with that in a cohortof matched controls. Another approach would be to look forchanges in the offspring of ultraviolet-deprived laboratory ani-mals.

Department of Psychiatry,University of Florida

School of Medicine,Gainesville, Florida 32610 U.S.A. RICHARD A. MOSKOVITZ

PURPLE URINE BOTTLES

SIR,-A 42-year-old woman presented with severe constipa-tion and abdominal pains which seemed to be exacerbated bysulphonamides and oral contraceptives. A urine sample putinto a plastic universal container became purple/red, so labora-tory investigations for porphyria were done. All were normal.

I am grateful to Mr Barlow and Mr Dickson for their

explanation (Jan. 28, p. 220) that the pigment might havebeen indigo and hope that others are not led down such anexpensive dead-end. ,

Manchester Victoria MemorialJewish Hospital,

Manchester M8 8TT T. E. G. JONES

1. Hillman, L. S., Haddad, J. G. Am. J. Obstet. Gynec. 1976, 125, 196.2. Hillman, L., Haddad, J.J. Pediat. 1974, 84, 742.3. Roberts, S. A., Cohen, M. D., Forfar, J. O. Lancet, 1973, ii, 809.