BDNF and post-traumatic stress disorder: Research findings examining emotional memory and the BDNF Val66Met SNP have been mixed26,27 with several review papers on BDNF, memory and PTSD noting that the literature is `consistently inconsistent’ and that several confounding variables may account for this inconsistency by influencing BDNF expression such as ethnicity, sex, estrogen32,33,63, and more recently, developmental stage of trauma40.