Delta-9-tetrahydrocannabinol (∆9-THC) is the major psychoactive component in the cannabis plant. THC acts on the cannabinoid 1 receptors (CB1Rs) of the endogenous cannabinoid system, which reaches peak expression during adolescence. Neuroimaging and behavioral evidence have shown that THC can induce psychotomimetic, perceptual, and cognitive effects after acute use, similar to the experience of altered state of consciousness (ASC) described in studies of classical psychedelics. This study sought to show that the standardized five dimensions of ASC rating scale (5D-ASC) is a sensitive measure of THC-induced ASC experience, and that 5D-ASC responses would be greater in younger infrequent users than in adults. We found that THC dose-dependently (15 mg, 7.5 mg vs. placebo) increased 5D-ASC responses and heart rate peak change in both adolescents (18-20 years old) and adults (30-40 years old). Within each age group, THC-induced heart rate responses were also positively correlated with most of the responses on 5D-ASC. Contrary to expectation, adolescents and adults did not differ on heart rate peak change after acute THC, but showed subtle differences on 5D-ASC responses. The current study was a preliminary study with only 25 participants in total. Trending differences were shown, but due to the number of subject recruited, we had limited statistical power. However, these findings provide the first insight into the use of 5D-ASC in assessing acute subjective effect after THC, and reveal that adolescents might experience greater sedative-like effects of THC than adults.