Personality traits that include being good at coping, altruistic, trusting, and honest make placebo treatment more likely to work as opposed to anger and hostility according to an article from the University of Michigan that was published in the journal Neuropsychopharmacology in November of 2012. Their study showed that about 25% of the placebo response was explained by traits of resiliency, straightforwardness, altruism on the one hand and anger and hostility on the other.
Where these researchers became confused is that they felt the "real" treatment was obscured by placebo responses when, of course, both are real responses! Mind power matters!
This study included 50 people between the ages of 19 and 38, and each person took a battery of psychological tests to identify the personality traits of interest. They were then injected with saline into their jaw muscle and told they would be injected with pain medication at certain times afterward. They then had PET scan to see how much endorphin was released. Cortisol levels were also measured to see if there was a correlation with endorphin secretion. They found that the endogenous endorphin release was clearly activated by placebo but cortisol levels were independent of placebo.
