The British Journal of Psychiatry 142: 560-565 (1983)
© 1983 The Royal College of Psychiatrists
Genetics of platelet MAO activity in discordant schizophrenic and normal twins
MA Reveley, AM Reveley, CA Clifford and RM Murray
Platelet monoamine oxidase (MAO) activity was compared in four age and
sex-matched groups: monozygotic (MZ) twins discordant for schizophrenia,
normal MZ twins, normal dizygotic (DZ) twins and unrelated individuals.
Among the twin groups, schizophrenic and normal there was a remarkably
consistent degree of genetic control amounting to 70-80 per cent of the
variation in activity. The mean platelet MAO activity of the schizophrenic
twins was significantly lower than that of controls, but not than that of
their psychiatrically well, neuroleptic-free cotwins; indeed the
correlation for the MZ twins discordant for schizophrenia was almost
exactly the same as that for the normal MZs. Thus, lower platelet MAO
activity in schizophrenia, where it is found, is genetically modulated and
not the result of the illness or its treatment.