Plasma CBD Concentrations Did Not Significantly Track Pain Reduction in the SCI Trial
The trial’s modest average CBD pain benefit did not coincide with a significant concentration–response association in its exploratory plasma analyses. Treatment assignment and measured plasma concentration answered different questions.
Parent CBD and metabolites were examined
The researchers analyzed plasma cannabinoid measurements and explored relationships between pain reduction and CBD or metabolite concentrations using correlations, regression and plotted trends. They reported no significant association for the examined concentration measures.
A group treatment effect need not produce a simple linear relationship
The randomized comparison estimated the effect of the treatment regimen relative to placebo. A correlation among measured concentrations asks whether differences in exposure align with differences in response. Sampling timing, variability, the selected dose range and limited sample size can constrain that second analysis.
The null did not define an effective concentration cutoff
The study did not establish a plasma level above which a person would reliably obtain pain relief. It also did not prove that exposure was biologically irrelevant. A scientific account should preserve both the controlled pain result and the concentration-analysis null, rather than deriving a therapeutic threshold from the group average. Plasma measurements are additionally distinct from direct brain concentrations or an assessment of impairment.
Related analysis: the study’s broader findings and limitations.
