Generally, inbreeding is associated with loss of biological fitness. For countries such as Iran, where consanguineous marriages are common,1 the association between consanguinity and intelligence is very important for public health programmes.

National IQs were calculated in relation to a mean IQ of 100 and standard deviation of 15 in Britain.2 The inbreeding coefficient is the probability that an individual has received both alleles of a pair from an identical ancestor. At the population level, the mean of inbreeding coefficient (α) was calculated for 35 countries. …