By Pat Anson, PNN Editor

Several studies have found that if you experienced physical or emotional trauma as a child you are more likely to have migraines, fibromyalgia and other painful conditions as an adult.

Australian researchers have taken that theory a step further, with a small study that found adults with a history of childhood abuse or neglect are more likely to feel the pleasurable effects of opioids, putting them at greater risk of addiction.

That finding, recently published in the journal Addiction Biology, is based on a double-blind, placebo-controlled study that compared the effects of morphine on 52 healthy people – 27 with a history of severe childhood trauma and a control group of 25 who had no such experiences as children.

Participants in both groups were given an injection of morphine or a placebo dose, and then asked how it made them feel. People in the trauma group reported more euphoria or feeling high and more “liking” of morphine. They also felt less nauseous and dizzy after taking the drug compared to the non-trauma control group.

“Those with childhood trauma preferred the opioid drug morphine and they felt more euphoric and had a stronger desire for another dose,” lead author Molly Carlyle, PhD, a research fellow at The University of Queensland, said in a statement. “Those with no childhood trauma were more likely to dislike the effects and feel dizzy or nauseous.

“This is the first study to link childhood trauma with the effects of opioids in people without histories of addiction, suggesting that childhood trauma may lead to a greater sensitivity to the positive and pleasurable effects of opioids.”

Researchers say people in the trauma group were significantly more likely to have a history of anxiety or depression, and to use over-the-counter pain relievers regularly.  They were also more likely to report stress, loneliness and less social support and self-compassion than the control group.

“One possible explanation for the differing responses to morphine is that childhood trauma affects the development of the endogenous opioid system – a pain-relieving system that is sensitive to chemicals including endorphins, our natural opioids,” Carlyle explained. "It's possible that childhood trauma dampens that system.

“When a baby cries and is comforted, endorphins are released, so if loving interactions like this don't happen, this system may develop differently and could become more sensitive to the rewarding effects of opioid drugs."

Pain was also measured during the study, with participants immersing a hand in cold water both before and after receiving morphine. Researchers measured how long it took for them to find the cold water painful and how long it took before they pulled their hand out. Morphine was found to increase pain threshold and tolerance in both groups, regardless of whether they experienced childhood trauma.

“The findings of this study are a stepping stone in highlighting the role of childhood trauma in OUD (opioid use disorder), emphasising the need to address trauma symptoms in this vulnerable group, and targeting early interventions at traumatised young people,” researchers concluded. “These findings have many clinical and social implications including reducing the guilt and shame common amongst those with OUD about the reasons behind the development of this damaging addiction.”