(HealthDay News) – An individual’s personality can explain a substantial portion of their placebo analgesic response, according to a study published online Nov. 16 in Neuropsychopharmacology.

Marta Peciña, MD, PhD, from the University of Michigan in Ann Arbor, and colleagues examined the ability of personality traits to predict response to a placebo after an experimental pain challenge in 50 healthy volunteers.

The researchers found that ego-resiliency, altruism, and straightforwardness were positive predictors, and angry hostility was a negative predictor, which could together explain 25% of variance in the placebo analgesic response. People scoring above the median on a composite of these traits experienced greater placebo-induced activation of µ-opioid neurotransmission in regions including the dorsal anterior cingulate cortex and the periaqueductal gray, which correlated with placebo-induced reductions in pain ratings. Reductions in cortisol levels were noted during administration of placebo, and correlated positively with decreases in pain ratings and endogenous opioid activation and negatively with angry hostility.

The results “suggest that simple trait measures easily deployable in the field could be utilized to reduce variability in clinical trials, but may also point to measures of individual resiliency in the face of aversive stimuli such as persistent pain and potentially other stressors,” Peciña and colleagues conclude.

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