Stratified Cannabis Duration Patterns Coexisted With a Null Overall Correlation
The paper described an inverse pattern after grouping participants by self-reported duration, while its unstratified correlation between baseline blood THC and duration was nonsignificant. Both findings belong in an accurate account.
The two analyses asked related questions differently
Baseline blood measurements were available for sixty-four participants. The authors divided participants into duration categories based on self-assessment and observed that higher starting THC tended to accompany shorter reported duration. Before stratification, the correlation analysis found no significant relationship, with p = 0.4736.
A grouped pattern does not erase the null result
The authors discussed variability as a possible explanation. That interpretation does not transform a nonsignificant overall correlation into a validated individual prediction. Small categories, variable exposures and the choice of grouping can affect how a pattern appears. Neither analysis directly establishes the causal effect of tolerance.
What a forensic claim should retain
Report whether the claim comes from the overall association or the duration categories, and identify self-report as the outcome. The study does not demonstrate that a high baseline concentration means someone will experience fewer functional effects after another dose. It also does not justify reversing that claim for a person with a low baseline. Blood concentration, perceived duration and measured driving performance remain different evidence types.
Related analysis: baseline and post-smoking breath findings.
Research cited
Wurz and DeGregorio (2022). Indeterminacy of cannabis impairment and THC levels in blood and breath. DOI: 10.1038/s41598-022-11481-5.
