Denne viser atnocebo effekten er like stor som placebo effekten.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4213146

The overall magnitude of the nocebo effect was moderate to large (lowest g = 0.62 (0.24-1.01) and highest g = 1.03 (0.63-1.43)) and highly variable (range of g = −0.43-4.05). The magnitudes and range of effect sizes was similar to those of placebo effects (d = 0.81) in mechanistic studies. In studies where nocebo effects were induced by a combination of verbal suggestions and conditioning, the effect size was larger (lowest g = 0.76 (0.39-1.14) and highest g = 1.17 (0.52-1.81)) than in studies where nocebo effects were induced by verbal suggestions alone (lowest g = 0.64 (−0.25-1.53) and highest g = 0.87 (0.40-1.34)). These findings are similar to those in the placebo literature. Since the magnitude of the nocebo effect is variable and sometimes large, this meta-analysis demonstrates the importance of minimizing nocebo effects in clinical practice.