An Analysis of the POINT Study

A recently released article titled the “Effect of cannabis use in people with chronic non-cancer pain prescribed opiates: findings from a 4-year long prospective cohort study” or POINT, published in the Lancet, Volume 3, No. 7, e341-e350, July 2018.

This study prospectively examined the cannabis use, opiate use, pain, pain-interference, perceived effectiveness, and some associations with mental health and drug abuse and dependence. This study evaluated people via survey at baseline, 3 months, and then annually for 4 years.

This study found no temporal association with subjective improved pain scores, pain interference, or decreased opiate use and also found a small association between cannabis use and drug dependence or abuse and mental health, although they say that this association needs to be evaluated carefully.  They also distinguished to some extent between self-identified or diagnosed neuropathic pain vs other pain and did find some differences in that grouping.

This is an important finding that contradicts much of the available evidence, however, there are some significant limitations to this study we should consider before considering it a definitive causative association.

First, during this study, there was no legal medical cannabis market or program and the cannabis was obtained illegally and its provenance was not considered as a part of its study.  Also, the manner of dosing was not considered (such as smoked, vaporized, or oral).  In addition, no dose of THC was included as a comparison to the morphine equivalents used.  So in many regards, this is a comparison of apples and oranges.  Cannabis, used illegally and without any measured dosing, is ineffective for pain is what this study truly analyzes.

Second, the number of patients who actually used cannabis during the study was very small relative to the population of the study.  Those who did not use cannabis numbered 1296 out of 1580 (82%).  Those who used at baseline were only 126 out of 1580 (~7.9%) and those who used cannabis after baseline were only 92 out of 1580 (~5.8%).  This to me means that this study did not have the power to evaluate effectiveness if less than 14% of the population studied ever used cannabis during the 4 years.  This is a severe weakness that calls into question the effectiveness of cannabis in pain.

Thirdly, although the study interpreted their results to mean that cannabis was ineffective in pain because it was not associated with temporal improvements in pain scores, other interpretations are possible.  Since correlation doesn't imply causation, the results could show that the small number of patients who took cannabis were also the ones with the worst pain scores.  That is, those with the most pain were more likely to take the risk to illegally obtain cannabis in an attempt to relieve their pain.  So, it could be that those in the worst pain and had the least improvement were simply more likely to try something else, rather than that cannabis had no effect on their pain.

Of note, those patients who did use cannabis self-reported that they believed cannabis helped and showed improvements in sleep and mood.  Although this is harder to measure, cannabis does seem to improve overall well-being regardless of effects on subjective pain scores.

So, although the results were statistically significant, the study lacks discriminatory power and they were comparing illegally used cannabis of unknown provenance and dose compared to known morphine equivalent doses.  Other interpretations of the data are also possible such as that those with the worst pain were more likely to risk illegally obtaining cannabis and may have been less likely to improve in their pain scores due to severity.  Although this study is important to consider as evidence in the overall medical case for or against cannabis as a pain medication, it is certainly not definitive and has many limitations.  

Ethan Carruthers