International Meeting for Autism Research (London, May 15-17, 2008): Familial Associations of Intense Preoccupations, an Empirical Factor of the Restricted, Repetitive Behaviors and Interests Domain of Autism

Familial Associations of Intense Preoccupations, an Empirical Factor of the Restricted, Repetitive Behaviors and Interests Domain of Autism

Saturday, May 17, 2008: 5:30 PM
Mancy (Novotel London West)
C. J. Smith , Research, Southwest Autism Research & Resource Center, Phoenix, AZ
C. M. Lang , Psychiatry, Mount Sinai School of Medicine, New York, NY
L. M. Kryzak , Psychiatry, Mount Sinai School of Medicine, New York, NY
E. Hollander , Psychiatry, Mount Sinai School of Medicine, New York, NY
R. Melmed , Research, Southwest Autism Research & Resource Center, Phoenix, AZ
J. M. Silverman , Psychiatry, Mount Sinai School of Medicine, New York, NY
Background: Clinical heterogeneity of autism likely hinders efforts to find genes, but promising results were obtained when samples were restricted to subjects that shared a common familial trait.  Previous studies have analyzed the factor structure of the restricted, repetitive behavior and interests (RRBI) domain and found a two-factor model, 'insistence on sameness' (IS) and repetitive stereotyped motor behaviors,' (RSMB) that accounted for a relatively small amount of variance.  Identifying additional familial factors that account for more variance may provide an approach to reduce heterogeneity in future studies.

Objectives: To a) replicate previous findings; b) identify new factors in the RRBI domain; c) examine their familiality among affected siblings; and, d) measure the association with broader autism phenotype (BAP) traits in their parents.

Methods: Our sample included 310 verbal subjects (age 5 to 22) who met DSM-IV criteria for autism.  We factor analyzed the RRBI 'ever' items from the Autism Diagnostic Interview-Revised to replicate previous findings and then in a separate analysis we included the communication item, 'verbal rituals.'  We examined the familial aggregation of factors and their association with BAP traits.

Results: The IS and RSMB two factor model was replicated in our sample.  In the second factor analysis (RRBI + verbal rituals) we observed a four factor model: IS, ‘simple’ RSMB, ‘complex’ RSMB, and a fourth factor including symptoms associated with intense preoccupations (IP).  IS and IP were each significantly familial (p < .001 for both), but only IP was significantly correlated with the BAP traits of rigidity (r = .39, p = .007) and aloofness (r = .39, p = .005) in fathers.

Conclusions: The results support previous evidence for the familiality of IS and identify IP as an additional strong candidate trait for genetic studies of autism.

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