Abstract Importance Autism Spectrum Disorders ASD aggregates in families, but the individual risk and to what extent this is caused by genetic factors, or shared or non-shared environment remains unresolved. Objective To provide estimates of familial aggregation of ASD. Design, Setting and Participants A population based cohort of all Swedish children born —
Twin studies[ edit ] Twin studies are a helpful tool in determining the heritability of disorders and human traits in general. They involve determining concordance of characteristics between identical monozygotic or MZ twins and between fraternal dizygotic or DZ twins.
Possible problems of twin studies are: A condition that is environmentally caused without genetic involvement would yield a concordance for MZ twins equal to the concordance found for DZ twins.
Assuming a general-population prevalence of 0. Notable twin studies have attempted to shed light on the heritability of autism. A small scale study in was the first of its kind to look into the heritability of autism. It involved 10 DZ and 11 MZ pairs in which at least one twin in each pair showed infantile autism.
In 12 of the 17 pairs discordant for autism, a biological hazard was believed to be associated with the condition. The twins developed similarly until the age of 4, when one of them spontaneously improved.
The other twin, who had suffered infrequent seizures, remained autistic. The report noted that genetic factors were not "all important" in the development of the twins. Eleven pairs of MZ twins and 10 of DZ twins were examined.
In most of the pairs discordant for autism, the autistic twin had more perinatal stress. The study concluded that "obstetric hazards usually appear to be consequences of genetically influenced abnormal development, rather than independent aetiological factors.
It found "poorer social cognition in males", and a heritability of 0. Neuroanatomical differences discordant cerebellar white and grey matter volumes between discordant twins were found. The study demonstrated significant aggregation of symptoms in twins.
It also concluded that "the levels of clinical features seen in autism may be a result of mainly independent genetic traits. It found that the siblings of autistic children, as a group, "showed superior spatial and verbal span, but a greater than expected number performed poorly on the set-shifting, planning, and verbal fluency tasks.
Prevalence of autism in siblings of autistic children was found to be 1. Prevalence of autism among siblings of children with Asperger syndrome or PDD was found to be 1.
The risk was twice as high if the mother had been diagnosed with a psychiatric disorder. The study also found that "the risk of autism was associated with increasing degree of urbanisation of the child's place of birth and with increasing paternal, but not maternal, age.
The simplest model was to divide parents into two risk classes depending on whether the parent carries a pre-existing mutation that causes autism; it suggested that about a quarter of autistic children have inherited a copy number variation from their parents.
Using standardized tests it was found that parents of autistic children were "more aloof, untactful and unresponsive" compared to parents whose children did not have autism. The study raised the possibility that the broader autism phenotype may include a "cognitive style" weak central coherence that can confer information-processing advantages.
It found that correlation for social impairment or competence between parents and their children and between spouses is about 0. Out of 64 siblings, 4 6.The heritability of autism is the proportion of differences in expression of autism Notable twin studies have attempted to shed light on the heritability of autism.
A small scale study in was the first of its kind to look into the heritability of autism. parental place of birth, parental age, family history of psychiatric disorders. These findings lend support to the validity of depression as a distinct condition in some children with autism/PDD and suggest that, as in the normal population, autistic children who suffer from depression are more likely to have a family history of depression.
They confirmed a raised familial loading for both autism and more broadly defined pervasive developmental disorders in siblings (% and %, respectively, vs 0% in the Down's group) and also evidence for the familial aggregation of a lsser'variant of autism, comprising more subtle communication/social impairments or stereotypic behaviours, but not mental retardation alone.
This study compared the family histories of 13 children with autism or pervasive developmental disorder (PDD) with depression and 10 similar children without depression.
Ten of the depressed children had a positive family history of depression compared to three of the nondepressed group.
Findings. Read "A Case‐Control Family History Study of Autism, The Journal of Child Psychology and Psychiatry" on DeepDyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips.
Read "A Case‐Control Family History Study of Autism, The Journal of Child Psychology and Psychiatry" on DeepDyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips.