The link between post-traumatic stress disorder (PTSD) and opioids is well established. About 40% of people with PTSD also have a drug-use disorder, and many people suffering from PTSD use opioid painkillers to self-medicate their PTSD symptoms. The connection could be even more insidious, though, according to a new study that suggests opioid use might actually cause PTSD.
Opioids as a PTSD Trigger
To test the effect of opioids on the development of PTSD, researchers at UCLA gave morphine, an opioid painkiller, to mice for a week. Following the doses of morphine, the researchers administered an electric shock to the mice. When the effects of the morphine had worn off, they gave the mice a second, milder shock.
The shocks triggered a fear response in the mice, but the morphine-treated mice were fearful for longer than a control group of mice that had not received an opioid. The prolonged fear response mimics PTSD in human patients, who suffer from physical fear responses even when there is no threat present.
Significantly, the prolonged fear response was triggered in the mice long after the morphine was gone from their systems. It appeared that the drug had caused a lasting change in their brains that was triggering PTSD.
“The ability of opioids to increase PTSD-like symptoms far outlasted the direct effects of the drug or withdrawal from the drug, suggesting the effect may continue even after opioid treatment has stopped,” says Michael Fanselow, PhD, the study’s senior author.
Fanselow and his team concluded that the mice’s prolonged opioid use made them more vulnerable to the stress caused by the initial electric shocks. That vulnerability translated into the PTSD symptoms the mice exhibited later.
The researchers also administered morphine to mice after the initial shock, but the later opioid dose didn’t increase the risk of PTSD. It appears that the timing of the opioid use is important. If the drugs are used before the traumatic event, the risk of PTSD is higher.
Risk Down the Road
The study’s implications are important for situations in which repeated trauma and stress are likely.
“As opioids are often prescribed to treat symptoms such as pain that may accompany trauma, caution may be needed because this may lead to a greater risk of developing PTSD, if exposed to further traumatic events, such as an accident, later on,” says Fanselow.
That means, for example, that treating soldiers with opioids following an injury might put them at risk for PTSD if they are sent back into combat after using the drugs. Further exposure to trauma could be much more likely to lead to PTSD.
Awareness of the link could also be important for healthcare providers caring for patients with a history of opioid abuse. Those patients might be especially in danger of developing PTSD if they encounter traumatic events later, and providers should be aware of the risks.