Attempts to identify the genetic causes of neurological and psychiatric disorders such as post-traumatic stress disorder (PTSD) through large-scale genome analyses have revealed thousands of potential links. The challenge has become more complex due to the wide range of symptoms experienced by individuals with PTSD.
For example, do the heightened arousal, anger, or irritability that some individuals experience share the same genetic basis as the tendency to relive traumatic events, which are other symptoms of the disorder? According to a new study led by researchers at Yale University and the University of California, answers to some of these questions have emerged, revealing intriguing genetic similarities between PTSD and other mental health disorders such as anxiety, bipolar disorder, and schizophrenia. The findings also suggest that commonly used medications for other disorders could be modified to help address the individual symptoms of multiple disorders. Co-author of the study, Professor Joel Gelernter, a professor of psychiatry, genetics, and neuroscience at Yale University, stated, "The complexity is still there, but this study helped us to untangle it."
For the study, researchers analyzed the complete genomes of over 250,000 participants in the Million Veteran Program, a national research program of the U.S. Department of Veterans Affairs that studies how genes, lifestyle, and military experiences affect the health and illness of military veterans. Nearly 36,000 participants had been diagnosed with PTSD. However, instead of only searching for genetic variants common to PTSD patients, the scientists looked for variants linked to three types of clinical symptoms experienced by patients to varying degrees. These symptom groups included reliving a traumatic event, excessive or severe anger and irritability, and avoiding people or topics that might be connected to past trauma.
While the researchers found common underlying genetic factors among the three symptom groups, they also discovered specific variants linked to just one or two of those symptoms. Gelernter noted, "We found a high degree of genetic correlation among these three symptom subdomains, although we do not expect them to be genetically identical, and they are not, of course. We also found biological support for the different clinical symptoms of PTSD."
Additionally, the study showed that some of these variants found in subgroups of patient symptoms were also linked to other disorders, such as major depression. The results indicated that medications used to treat other disorders might also be effective for PTSD. Co-author Moria Stein, a distinguished professor of psychiatry and public health at the University of California, remarked, "Our study suggested that some drugs currently prescribed for other conditions could be repurposed to treat patients with PTSD." Interestingly, variants associated with all PTSD symptoms were also linked to other neurological and psychiatric disorders. For example, variants related to PTSD were connected to the MAD1L1 gene, which helps regulate the cell cycle and has also been linked to schizophrenia and bipolar disorder.
