ABSTRACT
A twin study56 found no evidence for genetic transmission of GAD. A high frequency of non-anxiety psychiatric disorders in co-twins was observed. This indicates that GAD is probably aetiologically heterogenous. A second twin study57 was also negative, showing that genes contributed to the predisposition of personality traits, but not to specific diagnoses of GAD or panic. However, a third twin study58 produced a concordance for GAD among monozygotic twins versus dizygotic twins of 4.3:1, thus suggesting a genetic influence. Further, another study59 reported an increased rate of GAD (but not other anxiety disorders) in the first degree relatives of patients. Therefore, there may be a degree of familial transmission of the condition and differentiation from other anxiety disorders, such as panic,60 while GAD and depression appear to share, to a degree, the same genes.61
