A gene variant could cause worse depression, anxiety, and PTSD after TBI
A specific gene variant associated with Alzheimer’s disease may also carry a link with more severe psychiatric issues following a traumatic brain injury, according to a recent study conducted by the Veterans Affairs San Diego Healthcare System.
The report, in the Journal of Neurotrauma, found that study participants who had both the gene variant and at least one previous TBI showed worse symptoms of PTSD, anxiety, and depression, compared to a control group.
The recent research was inspired by a past study of more than 13,000 veterans by the Minneapolis VA Center for Chronic Disease Outcomes Research which found that more than 80% of people with TBI were also diagnosed for a psychiatric disorder. The same study also reported that veterans with a TBI were three times more likely to have PTSD.
The latest study reinforced those findings and also uncovered that patients with TBI had greater depression and anxiety symptoms.
The variant in question is a mutation of the APOE gene, which encodes the protein “Apolipoprotein E”. This protein helps transport and metabolize lipids like cholesterol in the central nervous system, as well as assisting in the maintenance, growth, and repair of neurons.
The APOE gene has three known possible variants, including one known as APOE4 which has been found to be a risk factor for Alzheimer’s disease. There is also evidence suggesting APOE may increase the risk of PTSD.
To assess whether the APOE4 gene could also play in a role in the outcome of individuals with TBI, the researchers collected DNA from 133 veterans of the wars in Afghanistan and Iraq. Of those participants, 79 had a mild to moderate TBI, while 54 had no history of brain injury.
Of those with TBI, individuals with APOE4 showed significantly higher symptom scores for PTSD, depression, and anxiety compared to those without the variant. This was consistent among both those with moderate and mild TBI.
Dr. Victoria C. Merritt, first author on the paper, concludes, “Genetic risk may help to explain the poorer long-term clinical outcomes often observed in veterans with neurotrauma histories.”
The team believes one possible explanation for why the APOE4 variant may place people at higher risk for psychiatric distress after TBI may be that the APOE4 variant primarily affects the frontal subcortical regions of the brain. These are also often affected by TBI. It is also possible that the variant increases the risk of vascular disease, which has been shown to be related to depression. It could also possibly be that the APOE4 variant simply causes neurodegenerative effects not caused by other variants of the gene.
While the findings suggest the APOE variant could play a significant role in the outcome of individuals with traumatic brain injury, the researchers say more work will be needed to fully understand how the gene interacts following head trauma.
“Ultimately, we feel that this research is essential to developing a more complete understanding of the multitude of factors that impact recovery following neurotrauma,” Merritt said, “and such work may have relevance to the development of future treatments.”