Genetic Counselling in Schizophrenia

Sir, On the basis of the data that they had collected, Parmeshwaran et al.(1999) concluded that a significant relationship exists between phases of the lunar synodic cycle and the development of psychiatric morbidity. From a methodological perspective, I have a reservation about their validity of their conclusions : Parmeshwaran et al.(1999) studied patients at the time of admission and not at the time of onset or exacerbation of symptoms. Since onset or exacerbation of symptoms is likely to precede admission by day to months, all that can be concluded from their data is that there appears to be an association between phases of the moon and the decision to present at psychiatric services. Such an association is very hard to explain on the basis of geomagnetic and other forces. From a theoretical perspective, I wish to point out that fluctuations in the gravitational field of the moon are very small; this is easily judged from the fact that the tidal effect is merely a few feet in height, on a body of water that is up to-6 miles deep. Therefore, the minor influence of the moon on biological functions is likely to be drowned out by the background noise generated by terrestrial biopsychosocial THE EDITOR variables or compensated for by neuropsychological and neurochemical homeostatic mechanisms. Finally, the authors use their full moon data to hypothesize that solar radition influences non-affective psychoses. They state that "the new moon must be obstructing a sufficient number of these charged particles from reaching the earth". This does not make sense because the visibility of the moon depends upon light reflected from the sun and because the new moon and full moon are nocturnal phenomena that occur when the sun is shining on the opposite side of the earth relative to the observer. The issue of the moon blocking solar radiation therefore does not arise.