CASE STUDY: Twin studies on OCD - Grootheest et al(2005)

In this meta-analysis, the researchers assessed 70yrs of twin studies into OCD. In a twin study MZ(Identical) twins are compared against DZ(non-identical) twins. If the chances of both twins in MZ pairs having OCD is greater than the DZ twins; it suggests a genetic component, as MZ are 100% genetically similar while DZ is 50%.

Aim: To see if there is any indication of the extent to which OCD is inherited & to see any difference of OCD inheritance between children & adults.

Procedure: Involved of twin studies of 2 broad types were reviewed -

1.'Old Literature' - comprising studies between 1922 - 1965, where it is not known if patients would be diagnosed with the disorder under modern diagnostic criteria.

2.'Studies meeting modern criteria' - comprising studies where patients were diagnosed under DSM criteria.

In all 10,034 twin pairs included in 28 twin studies formed the review.

Findings: Where methodology & statistical analysis were deemed sufficiently objective to gain useful data, it was estimated that in children OCD symptoms are heritable; ranging from 45 to 65%. For adults, OCD symptoms are heritable ranging from 27 to 47%.

Conclusions: Twin studies indicate a genetic component to the transmission of OCD. Heritability of OCD appears to be greater in children than among adults.

Evaluation: Need for further properly controlled twin studies to investigate as the majority were not performed in large enough numbers or under methodological conditions sufficient.

Need to include data from more gene mapping studies which look for similarities in genetic material in the DNA of sufferers & non sufferers.

	Created by Daryl Veerapahnaik about 8 years ago

A level Psychology (Psychopathology) Slide Set on Biological Approach to OCD & Treatments, created by Daryl Veerapahnaik on 08/08/2018.