text_1: Amitriptyline is an effective treatment for chronic tension-type headaches.
text_2: A reduction in headache duration and frequency of at least 50% was found in 39.4% on AO, in 25.4% on AM and in 26.6% on PL (PAO-PL = .1384, PAM-PL = 1.000, PAO-AM = .0973).