What determines our fate—nature or nurture? The truth is a combination of both. While recent studies show genes play a much larger role in who we become than previously thought, the expression of those genes depends on the environment. In one of the first studies to directly examine the influence of environmental factors on genetic predisposition for post-traumatic stress disorder (PTSD), a team of Yale researchers led by Robert H. Pietrzak, Associate Professor of Psychiatry and Public Health at Yale and Director of the Translational Psychiatric Epidemiology Laboratory of the Clinical Neurosciences Division of the U.S. Department of Veterans Affairs National Center for Posttraumatic Stress Disorder, found that the quality of interpersonal relationships can mitigate veterans’ risk of developing PTSD symptoms, providing new evidence of the interwoven roles of nature and nurture.
Motivated by previous findings on the importance of social connectedness as a protective force against PTSD, Pietrzak and colleagues set out to explore the role of a particular facet of connectedness—social attachment style. Those with a secure attachment style are more trusting, can form healthy relationships, and ask for help when needed. Comparing the polygenic risk score—a composite measure of several gene variants—of participants of the National Health and Resilience in Veterans Study, the team investigated how social attachment style interacts with genetic predisposition to predict the severity of PTSD symptoms. The gene variants of interest were associated with the PTSD symptom cluster, which includes intrusive thoughts, nightmares, flashbacks, and emotional and physiological reactivity to trauma reminders.
The researchers found that a secure attachment style neutralized genetic disposition for PTSD symptoms. A veteran with a high polygenic risk score for PTSD but a secure attachment style was no more likely to have symptoms than one with a low polygenic risk score. Furthermore, the association was bidirectional—while attachment style seems to have a buffering effect on PTSD symptoms, PTSD symptoms may also lead to a dissolution of social connections.
One gene, IGSF11, was associated with PTSD symptoms only in veterans with an insecure attachment style. IGSF11 has been implicated in the regulation of excitatory synaptic transmission in the brain as well as in neural plasticity, pointing to potential neurobiological mechanisms behind the mitigating effect of attachment style on PTSD symptoms.
The team hopes to further investigate these neurobiological mechanisms and explore the effects of different aspects of social connectedness on genetic risk for other mental health issues. These findings may also help inform treatment and more importantly, the prevention of PTSD. “All too often in the mental health field, interventions are implemented too late in people who have already developed problems,” Pietrzak said. His team plans to study the efficacy of interventions aimed at promoting secure attachment and mitigating genetic risk for PTSD.
For Pietrzak, these findings vindicate efforts to promote consideration of the interaction between nature and nurture in understanding risk for psychiatric disorders. “You cannot compute the area of a rectangle if you don’t know its length and width. It’s the same thing when it comes to the role of genes and the environment in shaping risk for disorders.”