Dose‐effect relations of mariiuana smoking on various physiological parameters in experienced male users Observations on limits of self‐titration of intake

The effects of smoking three different grades of marijuana (0, 0.5, and 2.9% Δ 9 tetrahydrocannabinol [THC]) were determined on various physiological subjective end pOints in experienced users tested blind at intervals of at least one week. The largest amount of Δ 9 THC equivalent taken by self‐titration was 31 mg. After 2.9% Δ 9 THC marijuana, clear thinking was significantly reduced, dizziness increased, palpebral fissures narrowed, and pupils slightly decreased. There was dose‐related increase in the amplitude of the patellar reflex and heart rate, significant at both dose levels. The 2.9% Δ 9 THC‐containing marijuana also slightly elevated systolic and diastolic blood pressure. Pulse rate changes were found to be correlated with subjective estimates of the marijuana “high.” Of the 18 subjects smoking the strongest material, 2 had panic reactions and 3 visual distortions and hallucinations. One subject became semicomatose. The majonty of subjects found their experience satisfying and reinforcing. One extremely heavy marijuana user tendea to show less effects than one less experienced user taking the same dose.