Twin study estimates of PTSD heritability range from 24 to 72% following trauma,6, 7, 8, 9 with female heritability two to three times higher than that in males.8 Twin studies have also documented that genetic influences on PTSD are shared with other mental disorders, particularly major depression.10, 11, 12 Such studies have made important contributions beyond heritability estimation; for example the discordant twin study by Gilbertson et al.13 showed that smaller hippocampal volume is likely a risk factor for PTSD rather than a consequence of the disorder. Despite this excellent work, the importance of genetic influences for PTSD etiology is not universally accepted among mental health clinicians or researchers. This may be in part because the latent modeling of genetic variation in twin studies is not easily interpretable to those not immersed in the methodology of behavioral genetics.
