Cannabis Initiation Was Carried Forward Across Waves in the Youth Study’s Main Analysis
The youth study’s primary cannabis-use indicator remained positive after first identified use. That variable represented an initiation history rather than a direct measure of active cannabis use or intoxication at every later cognitive assessment.
The coding rule followed first identification
Participants were coded as controls until self-reported use beyond a puff or taste, or positive cannabis toxicology, identified use. The indicator was then carried forward into later waves. Mid-year interview information was applied to the following main visit. This allowed the investigators to model trajectories around identified initiation.
An initiation indicator does not measure every later exposure
A participant remaining in the initiated category could have different subsequent frequency, amount or recency of use. The primary binary variable cannot establish a continuous exposure dose or intoxication at each test. A later positive category should therefore not be described as repeated toxicological confirmation at every assessment.
The secondary hair analysis used another rule
Hair cannabinoid groups were allowed to vary by wave and addressed more recent constituent-specific detection. Those analyses answered a related but different question from the main carried-forward indicator. A sound account states which exposure definition supports the cited result. This preserves the longitudinal design’s value while avoiding the assumption that all cognitive measurements after initiation were made during active cannabis effects.
Related analysis: the source’s broader findings and limitations.
