Fernández-de-las-Peñas C, et al. - Researchers examined the link between the rs4680 Val158Met polymorphism in frequent episodic tension-type headache (FETTH) and chronic tension-type headache (CTTH). In addition, they investigated how the rs4680 Val158Met polymorphism correlates with clinical, psychological, or psychophysical variables. They assessed the genotype frequencies and allele distributions based on restriction fragment length polymorphism in 50 women with FETTH, 50 with CTTH, and 50 matched headache-free women, after amplifying Val158Met polymorphism by polymerase chain reaction. They classified participants according to the Val158Met polymorphism rs4680genotype (Val/Val, Val/Met, or Met/Met). Outcomes suggested no significant differences in the distribution of rs4680 Val158Met genotype between women with/without headache, suggesting no involvement the Val158Met polymorphism (rs4680) in predisposition to tension-type headache. However, there appeared greater pressure pain sensitivity and higher depressive levels in CTTH carrying the Met/Met genotype that indicate a possible involvement of this genetic factor in the pathogenesis expression of CTTH.