Discordant monozygotic twin design Sample Clauses

Discordant monozygotic twin design. The discordant monozygotic (MZ) twin design is based on the fact that MZ twin pairs share 100% of their genetic background and also grow up sharing a number of environmental factors such as exposure to parental mental health problems, poverty and chaotic home environments (Xxxxxx, XxXxxxx, XxXxxxxx, & XxXxxxxx, 2001). As genetic and shared environmental factors are the same within a twin pair they can therefore not explain any differences observed amongst MZ twins. Differences between MZ twins can thus be traced back to exposure to unique environmental factors on which MZ twin pairs differ. For example one twin in a pair may have been bullied at school whilst the other twin has not. By investigating unique environmental exposure in relation to differences in behavioural development (i.e. differences in cognitive functioning), the discordant MZ twin design provides a unique tool for establishing a probable causal pathway between risk factors and children’s behavioural development. The design allows for probable causal pathways to be determined by methodologically controlling for the influence of genes and shared environmental experiences on behavioural development. It can further examine whether such associations are environmentally mediated and provide an insight into mechanisms underlying the link between risk factors and behavioural development (Xxxxx et al., 2004; Xxxxxx, Xxxxxxxx, & Xxxxxxxxxx, 2009). The discordant MZ twin design accounts for the confounding effect of genetic and environmental interplay (i.e. gene-environment correlation). As the genetic background is the same within a MZ twin pair, this design rules out the possibility that genetically influenced differences evoke different environmental exposure (Xxxxxx et al., 2009). Although the discordant MZ twin design accounts for genetic and shared environmental confounders, it does not rule out the possibility that there may be other correlated unique environmental factors which may explain the association between an observed unique environment and behavioural developmental outcome. For example, when investigating the unique environmental experience of being bullied with children’s cognitive functioning, other correlated unique environmental factors such as friendship group may also be a contributor. It is thus important to account for these correlated factors when employing the discordant MZ twin design. Furthermore, although the discordant MZ twin design assists in inferring probable causat...