Article

Autism as a Strongly Genetic Disorder: Evidence from a British Twin Study

MRC Child Psychiatry Unit, Institute of Psychiatry, London.
Psychological Medicine (Impact Factor: 5.94). 02/1995; 25(1):63-77. DOI: 10.1017/S0033291700028099
Source: PubMed

ABSTRACT

Two previous epidemiological studies of autistic twins suggested that autism was predominantly genetically determined, although the findings with regard to a broader phenotype of cognitive, and possibly social, abnormalities were contradictory. Obstetric and perinatal hazards were also invoked as environmentally determined aetiological factors. The first British twin sample has been re-examined and a second total population sample of autistic twins recruited. In the combined sample 60% of monozygotic (MZ) pairs were concordant for autism versus no dizygotic (DZ) pairs; 92% of MZ pairs were concordant for a broader spectrum of related cognitive or social abnormalities versus 10% of DZ pairs. The findings indicate that autism is under a high degree of genetic control and suggest the involvement of multiple genetic loci. Obstetric hazards usually appear to be consequences of genetically influenced abnormal development, rather than independent aetiological factors. Few new cases had possible medical aetiologies, refuting claims that recognized disorders are common aetiological influences.

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    • "The prevalence is considered to be 0.6–1.1 % (Levy et al. 2009; Baird et al. 2006; Hirtz et al. 2007) with a male:female ratio of 3–4:1 (Volkmar et al. 2004; Abrahams et al. 2007; Lai et al. 2015). According to multiple family and twin studies reporting a substantial heritable component ranging between 70 and 90 % of autism etiology (Bailey et al. 1995; Freitag 2011; Folstein and Rosen-Sheidley 2001), ASD is considered to be one of the most strongly genetically influenced multifactorial childhood psychiatric disorders (Hallmayer et al. 2011). Despite the high heritability, the genetics are inferred to be complex and no major gene has been identified to be relevant for the majority of ASD diagnoses (Freitag et al. 2010). "
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    ABSTRACT: The Contactin Associated Protein-like 2 (CNTNAP2) gene has been discussed to be associated with different symptoms of autism spectrum disorders (ASDs) and other neurodevelopmental disorders. We aimed to elucidate the genetic association of CNTNAP2 within high functioning ASD (HFA), focusing on autism specific symptoms and reducing intelligence related factors. Furthermore, we compared our findings conducting a meta-analysis in patients with ASD and HFA only. A case-control association study was performed for HFA (HFA, n = 105; controls, n = 133). Moreover, we performed a family-based association study (DFAM) analysis (HFA, n = 44; siblings, n = 57). Individuals were genotyped for the two most frequently reported single nucleotide polymorphisms (SNPs) in the CNTNAP2 gene (rs2710102, rs7794745). Furthermore, a meta-analysis using the MIX2 software integrated our results with previously published data. A significant association for the carriers of the T-allele of the rs7794745 with HFA was found in the case-control sample [OR = 1.547; (95 % CI 1.056-2.266); p = 0.025]. No association could be found by DFAM with any of the CNTNAP2 SNPs with HFA. The meta-analysis of both SNPs did not show a significant association with either ASD or with HFA. Overall, including case-control, sibs, and meta-analysis, we could not detect any significant association with the CNTNAP2 gene and HFA. Our results point in the direction that CNTNAP2 may not play a major role in HFA, but rather seems to have a significance in neurodevelopmental disorders or in individuals displaying intellectual delays.
    Full-text · Article · Nov 2015 · Journal of Neural Transmission
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    • "The diagnostic assessment for autism requires an elaborate screening process, which involves substantial consultations with many specialists and other physicians (Myers and Johnson 2007). The global prevalence of autism is estimated to be one in 160 people, and many studies have reported that the combination of genetic and environmental factors implicate a strong association in some aspects of ASD (Bailey et al. 1995; Campbell et al. 2006; Elsabbagh et al. 2012; Hallmayer et al. 2011); however, the development of ASD continues to be largely unclear. "
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    ABSTRACT: The presentation of allergic diseases in children with autism spectrum disorder (ASD) was evaluated systematically through a literature search using MEDLINE, EMBASE, Cochrane Library, and CINAHL databases. Any comparative studies on children with ASD and allergic diseases were evaluated for eligibility followed by risk of bias assessment, data synthesis, and meta-analysis. No randomized clinical trials were identified but 10 eligible observational studies were found, all of low methodological quality. A high estimated prevalence of asthma (OR 1.69, 95 % CI 1.11 to 2.59; 2,191 ASD children) and atopic rhinitis (OR 1.66, 95 % CI 1.49 to 1.85; 1,973 ASD children) were indicated. Rates of food allergy did not show significant differences between groups. Currently, clinical evidence was not found to draw any specific clinical implication.
    Full-text · Article · Oct 2015
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    • "In addition, they exhibit non-verbal communication problems as well. A rather high heritability of 80% [3] and a concordance rate in monozygotic twins of 70-90% compared to ~10% in dizygotic siblings [4] [5] strongly indicates a genetic determination of the disease. "
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    ABSTRACT: Autism spectrum disorder is a complex-genetic disease and its etiology is unknown for the majority of cases. So far, more than one hundred different susceptibility genes were detected. Voltage-gated calcium channels are among the candidates linked to autism spectrum disorder by results of genetic studies. Mutations of nearly all pore-forming and some auxiliary subunits of voltage gated calcium channels have been revealed from investigations of autism spectrum disorder patients and populations. Though there are only few electrophysiological characterizations of voltage-gated calcium channel mutations found in autistic patients these studies suggest their functional relevance. In summary, both genetic and functional data suggest a potential role of voltage-gated calcium channels in autism spectrum disorder. Future studies require refinement of the clinical and systems biological concepts of autism spectrum disorder and an appropriate holistic approach at the molecular level, e.g. regarding all facets of calcium channel functions.
    Full-text · Article · May 2015 · Current Molecular Pharmacology
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