MTHFR and migraine disorder: Early investigations into serotonin receptor variants (e.g., HTR1B G861C, T‐261G) and genes such as 5‐HTTLPR, MAOA‐VNTR, ESR1, MTHFR, ACE, TNF‐β, and GNB3 did not yield consistent associations with migraine or triptan response (MaassenVanDenBrink et al.