“…A large number of studies were also conducted with participant samples selected from community-based settings; in all but 1 study, these were with university students, particularly medical students in which higher than average rates of headaches were hypothesized. 1 , 8 – 10 , 18 , 24 , 33 , 42 , 49 , 50 , 52 , 55 , 58 , 59 , 72 , 73 , 90 , 102 Rates of both headache types ranged widely, again likely because of methodological differences and uncontrolled biases, such as selective sampling. Migraine rates varied from 6.4% to 28.5% 1 , 8 – 10 , 18 , 24 , 42 , 49 , 52 , 55 , 58 , 59 , 72 , 73 , 90 , 102 and TTH rates varied from 12.8% to 66.8%.…”