>>That placebo effect study is 20 years old.
>Has it been contradicted anywhere? I don't see any other studies that have looked into it.
Somewhat tangentially, and not specific to Parkinson's or DBS, but placebo has been getting stronger for at least some classes of treatment. E.g.:
Tuttle AH, Tohyama S, Ramsay T, Kimmelman J, Schweinhardt P, Bennett GJ, Mogil JS. Increasing placebo responses over time in U.S. clinical trials of neuropathic pain. Pain. 2015 Dec;156(12):2616-2626. doi: 10.1097/j.pain.0000000000000333. PMID: 26307858.
Walsh BT, Seidman SN, Sysko R, Gould M. Placebo Response in Studies of Major Depression: Variable, Substantial, and Growing. JAMA. 2002;287(14):1840–1847. doi:10.1001/jama.287.14.1840
So I would not be surprised if placebo got stronger in this area as well.
Somewhat tangentially, and not specific to Parkinson's or DBS, but placebo has been getting stronger for at least some classes of treatment. E.g.:
Tuttle AH, Tohyama S, Ramsay T, Kimmelman J, Schweinhardt P, Bennett GJ, Mogil JS. Increasing placebo responses over time in U.S. clinical trials of neuropathic pain. Pain. 2015 Dec;156(12):2616-2626. doi: 10.1097/j.pain.0000000000000333. PMID: 26307858.
Walsh BT, Seidman SN, Sysko R, Gould M. Placebo Response in Studies of Major Depression: Variable, Substantial, and Growing. JAMA. 2002;287(14):1840–1847. doi:10.1001/jama.287.14.1840
So I would not be surprised if placebo got stronger in this area as well.