DNA Methylation in Repetitive Elements and Post-Traumatic Stress Disorder: A Case–Control Study of US Military Service Members

Abstract

Aim: We investigated serum DNA methylation patterns in genomic repetitive elements, LINE-1 and Alu, for post-traumatic stress disorder (PTSD) cases and controls who were US military service members recently deployed to Afghanistan or Iraq. Methods: Cases (n = 75) had a postdeployment diagnosis of PTSD. Controls (n = 75) were randomly selected service members with no postdeployment PTSD diagnosis. Pre- and post-deployment sera were accessed, DNA was extracted and DNA methylation (percentage 5-methyl cytosine) was quantified via pyrosequencing. Conditional and unconditional logistic regressions were used to compare: cases post- to pre-deployment; controls post- to pre-deployment; cases to controls predeployment; cases to controls postdeployment. Results: LINE-1 was hypermethylated in controls post- versus pre-deployment (odds ratio [OR]: 1.33; 95% CI: 1.06–1.65) and hypomethylated in cases versus controls postdeployment (OR: 0.82; 95% CI: 0.67–1.01). Alu was hypermethylated for cases versus controls predeployment (OR: 1.46; 95% CI: 1.08–1.97). Conclusion: Patterns of hypermethylation of LINE-1 in controls postdeployment and of Alu in cases postdeployment are intriguing and may suggest resilience or vulnerability factors.

KEYWORDS::

• Alu
• combat
• DNA methylation
• epigenetics
• LINE-1
• Operation Enduring Freedom
• Operation Iraqi Freedom
• post-traumatic stress disorder
• repetitive element

Financial & competing interests disclosure

This study was funded by a Congressionally Directed Medical Research Program Grant, W81XWH-08-2-0053. A Baccarelli received support from the Search Results National Institute of Environmental Health Sciences – Harvard School of Public Health Center for Environmental Health New Investigator Fund (P30ES000002). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Additional information

Funding

This study was funded by a Congressionally Directed Medical Research Program Grant, W81XWH-08-2-0053. A Baccarelli received support from the Search Results National Institute of Environmental Health Sciences – Harvard School of Public Health Center for Environmental Health New Investigator Fund (P30ES000002). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. No writing assistance was utilized in the production of this manuscript.