Correlates of self-injurious, aggressive and destructive behaviour in children under five who are at risk of developmental delay.

AIM: Several behavioural correlates of self-injury, aggression and destructive behaviour have been identified in children and young adults with intellectual disabilities. This cross-sectional study aimed to further explore these correlates in very young children with developmental delay. METHODS: Parents of 56 children (40 male) under the age of five years (mean age 2 years 10 months) completed a questionnaire about their child's behaviour and the presence of behavioural correlates, including repetitive, over-active or impulsive behaviour and more severe developmental delay. RESULTS: Parents reported very high prevalence of self-injurious, aggressive and destructive behaviour: 51%, 64% and 51%, respectively. A binary logistic regression revealed that a higher score on a measure of overactive and impulsive behaviour significantly predicted the presence of destructive behaviour. A multiple linear regression revealed that both repetitive behaviour and number of health problems approached significance as independent predictors of severe self-injurious behaviour. INTERPRETATION: Despite the very small sample, several factors emerged as potential predictors of self-injurious, aggressive and destructive behaviour. These findings support the need for further investigation in a larger sample. Confirmation in this age group could help guide the development of targeted early intervention for these behaviours by identifying behavioural risk markers.

Evidence from Turner's syndrome of an imprinted X-linked locus affecting cognitive function.

Turner's syndrome is a sporadic disorder of human females in which all or part of one X chromosome is deleted. Intelligence is usually normal but social adjustment problems are common. Here we report a study of 80 females with Turner's syndrome and a single X chromosome, in 55 of which the X was maternally derived (45,X[m]) and in 25 it was of paternal origin (45,X[p]). Members of the 45,X[p] group were significantly better adjusted, with superior verbal and higher-order executive function skills, which mediate social interactions. Our observations suggest that there is a genetic locus for social cognition, which is imprinted and is not expressed from the maternally derived X chromosome. Neuropsychological and molecular investigations of eight females with partial deletions of the short arm of the X chromosome indicate that the putative imprinted locus escapes X-inactivation, and probably lies on Xq or close to the centromere on Xp. If expressed only from the X chromosome of paternal origin, the existence of this locus could explain why 46,XY males (whose single X chromosome is maternal) are more vulnerable to developmental disorders of language and social cognition, such as autism, than are 46,XX females.