One of the greatest public health issues facing the country is the worsening opioid epidemic. Prescription opioids are the first line of pain treatment following surgery or other pain-related conditions. The benefit of these drugs is that they work, at least in the short term. But overtime, tolerance to the drug develops, requiring the user to consume more and more of the drug to achieve pain relief. This tolerance results largely from a reduction in the number of opioid receptors in the brain and spinal chord that mediate the drug’s effects. Tolerance also results from the reduction in the body’s own opioid chemicals. Since opioid chemicals binding to their receptors dampens pain signals, tolerance reflects the weakened inhibition of pain signals that reach the brain. Consequently, the user seeks more and more drug, eventually turning to more powerful opioids like heroin and fentanyl.
So where does cannabis come in?
You may have heard that states with legal cannabis access have fewer opioid-related overdoses. This is true, but its merely an association and doesn’t speak to why this association exists. Until this past year, it was unclear if cannabis itself played a role.
However, recent studies have demonstrated that cannabis can:
- Substitute for opioid medications for pain treatment
- Reduce the amount of prescription opioids needed to achieve pain relief
How might cannabis be achieving these effects?
On its own, THC activates cannabinoid type I receptors (CB1) which can reduce excitatory brain signaling in pain-pathways. But cannabis’ greatest pain-relieving benefits are thought to be largely through interaction with the body’s opioid system.
One proposed mechanism is that THC may enhance the effect of opioids themselves (both endogenous opioids produced by the body and exogenous opioids in medications). At the cellular level, activation of CB1 receptors by THC increases the activity of mu-opioid receptors, which dampen pain signals. Studies investigating this mechanism find that low doses of THC can lead to substantial reductions in pain when paired with low doses of morphine. On their own at those doses, neither THC nor morphine relieve pain, but together, they have a synergistic effect, in which their effect is greater than the sum of each.
This is important, because these drug doses are below the threshold that leads to tolerance. By achieving pain relief, without inducing tolerance, cannabis can help protect against the spiral towards greater and harder opioid use.
CBD also can reduce pain through its potent anti-inflammatory properties. By shutting down inflammation, CBD reduces the production of pain-causing proteins. Thus, cannabis containing both THC and CBD are found to be better pain relievers than either on their own, likely by acting on multiple pain-relieving mechanisms.
Current research is looking to identify the long-term consequences of co-administration of cannabis and opioids on brain health. Scientists are also investigating how CB1 and mu-opioid receptors interact to produce synergistic effects when activated.
For a further look at cannabis in pain, check out my articles covering the topic: