BDNF and Headache: Among patients aged 18–64, chronic pain (OR = 1.6, 95% CI 1.05–1.28, p = ***) was the leading risk factor most strongly associated with PCS in addition to headache (OR = 1.36, 95% CI 1.03–1.80, p = *) and BDNF (Val66Met; OR = 1.30, 95% CI 1.00–1.69, p = *).