Is child intelligence associated with parent and sibling intelligence in individuals with developmental disorders? An investigation in youth with 22q11.2 deletion (velo-cardio-facial) syndrome.

[22q11.2 deletion syndrome]

Children with 22 q 11 .2 deletion syndrome (22 q 11 DS ), a copy-number variation (CNV ) genetic disorder , demonstrate a great deal of variability in IQ scores and are at particular risk for cognitive difficulties , with up to 45 % experiencing intellectual disability . This study explored the IQ relationship between individuals with 22 q 11 DS , their parents and their siblings . Participants included individuals with 22 q 11 DS , unaffected siblings and community controls , who participated in a longitudinal study of 22 q 11 DS . Significant associations between proband and relative (parent , sibling ) IQ scores were found . Results suggest that the cognitive functioning of first -degree relatives could be a useful marker of general genetic background and /or environmental effects , and can explain some of the large phenotypic variability in 22 q 11 DS . These findings underscore the importance of including siblings and parents in studies of 22 q 11 DS whenever possible .