Three studies involving a total of 63 Ss (aged 23-59 yrs) examined factors contributing to headache reduction 6 mo after treatment. Ss were migraine sufferers who had originally been treated with either peripheral skin temperature biofeedback, biofeedback for blood-volume-pulse amplitude of the temporal artery, or applied relaxation. In Study 1, biofeedback Ss who had achieved self-control of the trained physiological parameter had greater headache reductions than "nonlearners." In Studies 2 and 3, potential predicting factors of clinical effects were studied. Age and whether Ss had achieved self-control emerged as weak predictors. Using partial least squares projections to latent structures, a model emerged which gave a more complex picture and which might indicate that there are different sets of factors which predict success and nonsuccess in treatment
.