Biological explanation - genetic predisposition Flashcards
What does this explanation state?
- states that those with AD have a genetic predisposition to the disorder
family studies and twin studies are used to investigate
Family and twin studies
Szatmari (1999) combined data from several family studies to calculate the sibling risk - risk was found to be 2.2%
Bailey et al (1995) analysed data from the british twin study
- concordance rate for MZ twins was 60% and DZ twins was 0%
- the researchers then widened the definition of autistic behaviours to include other characteristics and found 92% concordance for MZ` AND 10% for DZ
Ritvo et al found concordance rates of 96% for MZ twins and 23% for DZ twins
Simplex or multiplex
- in some families only 1 member has ASD known as simplex ASD
- in multiplex ASD families, either more than one member has a diagnosis of ASD or several have autistic traits
it is thought that the mechanism of genetic vulnerability differs in simplex and multiplex families
multiplex - ASD is caused by genetic variations that are inherited
simplex - new genetic mutations occur when sequences of the DNA are duplicated at fertilisation
- affects multiple genes which are called copy number variations (CVNS)
CNVs account for 10% of all diagnosed case of ASD
Syndromic and non syndromic
ASD can be diagnosed on its own which is known as non syndromic and it is unclear what the underlying genetic cause is
