Pain research has always focused on opioids over cannabinoids. I analyzed trends in scientific publications to find out by just how much.

Opioids have been used to relieve pain for millenia, but they are not without their problems. We are currently in an opioid abuse epidemic and many users first develop a dependence problem when they are legitimately prescribed opioids for pain.

However, we at least have a very good idea of what types of pain opioids work well for and the types of pain where they are not efficacious. The number of studies that have been performed on opioids is staggering.

On the other hand, cannabinoid research stagnated for many decades. Only recently has it started to pick up again, particularly when it comes to clinical testing. However, as one of my prior analyses showed, NIH funding does not make a strong investment in therapeutic cannabinoid research.

To get a better idea of just how much pain research has focused on opioids over cannabinoids, I analyzed trends in scientific publications in Pubmed. What I found shows just how much cannabinoid research has been neglected over the last several decades.

Assessment of pain research on Pubmed

To see how much basic and clinical pain research has focused on each class of drugs, I performed the following searches on PubMed:

cannabinoid AND pain

opioid AND pain

I first searched for all results, then filtered by Review (an article that summarizes the current state of knowledge on a topic) and then by Clinical Trial. I downloaded the number of citations per year in each category. To calculate the number of Basic Research publications, I subtracted the Clinical Trial count and the Review count from the total number of results.

Opioids vs. cannabinoids in pain research

The cannabinoid + pain search revealed 2,261 citations, but the opioid + pain search resulted in 43,956 citations – 19.4 times more!

Next, I looked at trends in publications over time. It is clear that there has been a gradual increase in Basic Research publications of opioid and cannabinoids. However, opioid publications have been increasing since the 70’s and the increase for cannabinoids really only started in the mid-90’s.

Publications in Clinical Research have increased steadily for opioids over 40 years, but the same cannot be said about cannabinoids. Although there has been an increase in publications over the last 10 years, it is so small that it can barely be seen in the plot.

In the prior plot, it can be difficult to get a sense of just how many more pain publications are focused on opioids. So next, I plotted the ratio of opioid to cannabinoid publications over time and grouped the data into decades.

You can see that the 80’s were just a terrible time for cannabinoid research. An astounding 248 times more opioid publications in Basic Research were published on pain. Even worse, not one single paper was published for cannabinoids in Clinical Research (hence the ratio with opioid publications is infinite).

Since the 80’s, there have been relatively more pain publications on cannabinoids. However, these scientific publications are still in the minority. So far this decade, there are 12 times more Basic Research publications focused on opioids and 55 times more Clinical Research publications focused on opioids.

What is the right ratio of opioid and cannabinoid research?

This is a question that is nearly impossible to answer.

At this point, there are many different opioid medications on the market and they are the standard of care for many types of pain. There are naturally going to be more studies of these existing medications for a long time to come.

However, opioids do not work well for all types of pain. People taking opioids also have a relatively high risk of developing dependence, as our current opioid epidemic shows. We should be studying all possible treatment options to provide the best information to patients and caregivers so that they can make well-informed choices.

Many people with chronic pain feel that they have an improved quality of life using cannabinoids compared to using opioids. However, there are still many outstanding questions about the efficacy of cannabinoids in various types of pain. Not many controlled clinical trials have been performed and without these data, cannabinoids will not be accepted into common medical practice.

Please let me know in the comments what you think! Is the balance between opioid and cannabinoid research right or is time for a shift to more investment in cannabinoid research?