Can a placebo response result in major effects?
Here are some really interesting examples….
“In a British study, 835 women who regularly used analgesics for headache were randomly assigned to one of four groups (43). One group received aspirin labeled with a widely advertised brand name (‘one of the most popular’ analgesics in the United Kingdom that had been ‘widely available for many years and supported by extensive advertising’). The other groups received the same aspirin in a plain package, placebo marked with the same widely advertised brand name, or unmarked placebo. In this study, branded aspirin worked better than unbranded aspirin, which worked better than branded placebo, which worked better than unbranded placebo. Among 435 headaches reported by branded placebo users, 64% were reported as improved 1 hour after pill administration compared with only 45% of the 410 headaches reported as improved among the unbranded placebo users. Aspirin relieves headaches, but so does the knowledge that the pills you are taking are ‘good’ ones.” 
“The classic example of the meaningful effects of surgery comes from two studies of ligation of the . . . arteries as a treatment for angina (63, 64). Patients receiving sham surgery did as well – with 80% of patients substantially improving—as those receiving the active procedure in the trials . . . Although the studies were small, the procedure was no longer performed after these reports were published.” 
(43). Branthwaite A, Cooper P. Analgesic effects of branding in treatment of headaches. Br Med J (Clin Res Ed). 1981;282:1576-8.
. Moerman DE, Jonas WB. Deconstructing the placebo effect and finding the meaning response. Ann Intern Med 2002 Mar 19;136(6):471-6.