Adolescents Were More Cognitively Impaired by THC Than Adults at the Same Doses | Research

The takeaway

At THC doses that produced similar subjective intoxication in both groups, adolescents showed dose-dependent cognitive impairments and brain changes that adults did not, suggesting greater vulnerability.

Young cannabis users, parents, neuroscientists, policymakers

Adolescents more impaired despite similar subjective intoxication

What the researchers found

Adolescents (18-20) showed dose-dependent impairments in reaction time, response accuracy, and time perception with THC (7.5 and 15 mg) that adults (30-40) did not exhibit. THC decreased P300 brain wave amplitude in adolescents but not adults. Subjective intoxication and heart rate effects were similar in both groups.

Why it matters

This is one of the first human studies directly comparing THC effects across age groups. The finding that adolescents are more cognitively impaired at doses that feel the same as for adults has important implications for risk communication.

The numbers in context

12 adolescents (18-20) vs 12 adults (30-40); THC 7.5 and 15 mg; <20 lifetime uses; dose-dependent cognitive impairment in adolescents only; P300 decreased in adolescents only

How the study worked

Double-blind, placebo-controlled RCT with 12 adolescents (18-20) and 12 adults (30-40), all with fewer than 20 lifetime THC uses. Each received placebo, 7.5 mg, and 15 mg THC capsules across three sessions.

What this study cannot tell us

Very small sample (24 total). Participants aged 18-20 are legally adults but neurologically still developing. Oral THC capsules may differ from smoked/vaped cannabis.

How to read the evidence

Well-designed double-blind RCT with objective cognitive and EEG measures, but very small sample size (24 total).

When this study was published

Published in 2022

The bigger picture

This study provides human evidence for what animal studies have long suggested: the adolescent brain is more vulnerable to THC. The dissociation between feeling equally high and being more impaired is particularly concerning.

Questions still open

Would these differences persist with regular cannabis use and tolerance development? Does the P300 reduction in adolescents reflect long-lasting brain changes or only acute effects?

Common questions

Are young people more affected by THC than adults?

Yes. This study found adolescents (18-20) had dose-dependent impairments in reaction time, accuracy, and time perception that adults (30-40) did not show, even though both groups reported feeling equally intoxicated.

Why is this concerning?

If adolescents feel equally high as adults but are more impaired, they may not recognize their cognitive deficits. This could lead to risky decisions like driving while more impaired than they realize.

Read the original research

Adolescents are more sensitive than adults to acute behavioral and cognitive effects of THC.

Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 47(7), 1331-1338

View on PubMed ↗Publisher’s paper ↗

Citation

Murray, Conor H; Huang, Zhengyi; Lee, Royce; de Wit, Harriet. (2022). Adolescents are more sensitive than adults to acute behavioral and cognitive effects of THC.. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 47(7), 1331-1338. https://doi.org/10.1038/s41386-022-01281-w