PeterZeeberg, Danish Headache Center, Dept. of Neurology, Univ. Copenhagen, Glostrup Hosp., Nordre Ringvej 57, DK-2600 Glostrup, DENMARKPeter.Zeeberg@Dadlnet.dk
Jes Olesen, Rigmor Jensen
Submitted August 31, 2006
Dr. Gotkine’s question highlights an important aspect of all pain
research – the placebo effect. Due to the uncontrolled
open study design, we can not rule out the possibility of an
"inverse" placebo effect. There are, however, several reasons to believe
that this possible "inverse" placebo effect is minimal in our study.
In
prophylactic migraine trials, the reduction in migraine attacks due to
placebo response has been estimated to 16.8% [3], but with large variation
between studies. In acute migraine attacks, the average headache response
rate to placebo is even higher (30%). [4]
If a significant placebo effect was present, one would expect it to be
evenly distributed among all patients and across different headache
diagnoses.
Our patients segregated into three groups following
withdrawal: one with improvement (45%); one that stayed completely
unchanged (48%); and a small group of 7% who deteriorated. Furthermore,
there were marked differences between the diagnostic groups with a 67%
median reduction in migraine, 0% in tension-type headache (TTH), 37% in
mixed migraine and TTH and 0% in other headache diagnoses. These results
strongly suggest the absence of a marked “inverse” placebo effect.
References
3. van der Kuy PH, Lohman JJ. A quantification of the placebo
response in migraine prophylaxis. Cephalalgia 2002;22:265-70.
4. Bendtsen L, Mattsson P, Zwart JA, Lipton RB. Placebo response in
clinical randomized trials of analgesics in migraine. Cephalalgia
2003;23:487-90.
Disclosure: The authors report no conflicts of interest.
Dr. Gotkine’s question highlights an important aspect of all pain research – the placebo effect. Due to the uncontrolled open study design, we can not rule out the possibility of an "inverse" placebo effect. There are, however, several reasons to believe that this possible "inverse" placebo effect is minimal in our study.
In prophylactic migraine trials, the reduction in migraine attacks due to placebo response has been estimated to 16.8% [3], but with large variation between studies. In acute migraine attacks, the average headache response rate to placebo is even higher (30%). [4] If a significant placebo effect was present, one would expect it to be evenly distributed among all patients and across different headache diagnoses.
Our patients segregated into three groups following withdrawal: one with improvement (45%); one that stayed completely unchanged (48%); and a small group of 7% who deteriorated. Furthermore, there were marked differences between the diagnostic groups with a 67% median reduction in migraine, 0% in tension-type headache (TTH), 37% in mixed migraine and TTH and 0% in other headache diagnoses. These results strongly suggest the absence of a marked “inverse” placebo effect.
References
3. van der Kuy PH, Lohman JJ. A quantification of the placebo response in migraine prophylaxis. Cephalalgia 2002;22:265-70.
4. Bendtsen L, Mattsson P, Zwart JA, Lipton RB. Placebo response in clinical randomized trials of analgesics in migraine. Cephalalgia 2003;23:487-90.
Disclosure: The authors report no conflicts of interest.