The effect of consanguineous marriage on reading disability in the Arab community.

The present study examined the effect of consanguineous marriage in the Arab community on reading disabilities of offspring. It examined whether the rate of reading disabilities was higher among offspring of first-cousin parents than offspring of unrelated parents; and whether reading-disabled children of first-cousin parents were more disabled in phonological awareness and phonological decoding than reading-disabled children of unrelated parents and normally reading younger children. These questions were investigated among 814 pupils of the 4th, 5th, and 6th grades, using word recognition and reading comprehension tests. Two experimental groups were chosen from this population. These were a reading-disabled group of 22 pupils who were children of first-cousin marriages and 21 pupils who were children of unrelated parents. A control group was also selected, consisting of 21 younger normally reading pupils at the same reading level. All the groups were tested on non-words, real words, phonological, orthographic and working memory measures. The results indicated that the rate of reading disabilities among children of first-cousin parents was higher than that of with children of second-cousin parents, distantly related parents, or unrelated parents. Further, no differences were found in phonological awareness and decoding between the two reading-disabled groups. Moreover, the results indicate a significant advantage of the younger normal readers over the reading-disabled children in the measures of phonological awareness, decoding, and orthographical knowledge that requires spelling. However, in reading common words and choosing words in context, the performance of the reading-disabled groups and the normally reading group were similar. It has been suggested that further research is needed to evaluate the role of intelligence, nevertheless our results provide new evidence for a genetic basis to reading disabilities.