Post-hoc genotype analysis of PDM severity on global (A) and subfield (B) hippocampal volumes. Neuroprotective effect of the Val variant of BDNF Val66Met polymorphism on hippocampus in subjects with moderate menstrual pain. Post-hoc genotype analysis on global and subfield hippocampal volumes revealed that only subjects with moderate PDM demonstrated a positive Val allele dosage effect on the hippocampus. Note that the effects were particularly evident in the right whole hippocampus, subiculum, and molecular layer subfields. All volumetric data were adjusted by age, concentration of estradiol, and total brain gray matter volume. Bar graphs show means and SEM. *p < 0.05; **p < 0.01, post-hoc Bonferroni test.