Family studies have shown high evidence for the genetic basis for Autism Spectrum Disorders (ASD). In this context, there is an increasing interest in the study of ASD siblings (Bishop et al., 2006). There is quite literature of social and communicative deficits in ASD siblings (Constantino, 2006) but little referred to cognitive traits. Some previous studies have shown impairments in executive functions in ASD siblings (Delorme, 2007; Hugues 1999) but others studies did not find these results (Sumiyoshi 2011, De la Marche 2012).
To examine the clinical, cognitive and adaptive profile of a sample of high-functioning ASD (HF-ASD) children and adolescents and their siblings compared to normal-developing children.
25 children and adolescents with HF-ASD, 19 HF-ASD siblings (SIB) and 25 typical-developing children and adolescents (TD) were assessed. The three groups did not differ in age (HF-ASD=12.34, SD=3.05; SIB=13.45, SD=4.86, TD=12.51, SD=3.13), socioeconomic status nor IQ (HF-ASD=101.08, SD=15.90; SIB=102.88, SD=15.31, TD=109.08, SD=11.89). HF-ASD patients and TD subjects were matched in sex. The ASD diagnosis was confirmed using the ADI-R and DSM-IV criteria. The Kiddie-SADS was administered to assess the presence of psychiatric diagnosis. Neuropsychological assessment was administered by an experienced psychologist blind to the status of the subjects (verbal memory –VM-, visual memory and visuospatial habilities –Vis-, working memory –WM-, processing speed –PS-, executive functions –EF-). A general cognitive domain (GC) was calculated as the mean of all cognitive domains. Vineland Adaptive Behavior Scale (VABS) and BRIEF were administered to evaluate real-world functioning.
SIB group showed a higher percentage of subjects with a psychiatric diagnosis than TD children (SIB: 42%, χ2 corrected =7.434, p=0.006). Two siblings meet criteria for ASD and were excluded of further analyses. The other diagnoses were ADHD and Anxiety Disorders.
HF-ASD patients showed more difficulties than TD subjects in GC (F=8.985, p<0.001, post-hoc Bonferroni p<0.001) and in all cognitive domains but not in VM (Vis: F=4.032, p=.023, post-hoc Bonferroni p=.036; WM: F=4.024, p=.023, post-hoc Bonferroni p=.020; PS: F=5.783, p=.005, post-hoc Bonferroni p=.007; EF: F=4.781, p=.012, post-hoc Bonferroni p=.018). When compared with their siblings, HF-ASD showed more difficulties in GC (p=0.010) and in PS (p=.041), but not in VM, WM, EF and Vis. No significant differences were found between SIB and TD groups.
HF-ASD group showed more impairments than TD subjects and than SIB group in VABS (F=25.828, p<0.001, post-hoc Bonferroni p<0.001). They also showed impaired real-world executive functioning when compared with both TD and SIB (F=26.070, p<0.001, post-hoc Bonferroni p<0.001). No significant differences were found between the SIB group and the TD subjects in functioning measures.
HF-ASD children showed generalized cognitive and real-world adaptive deficits. The siblings of HF-ASD participants showed a higher rate of psychiatric disorders than the control group. Cognitive assessment revealed that there were less differences between HF-ASD subjects and their siblings than between HF-ASD and TD group, although siblings did not differ significantly from TD subjects neither in cognitive domains nor real-world adaptive functioning. These preliminary results support the need of an accurate clinical evaluation of HF-ASD siblings.
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