A single low dose of IV THC caused symptoms in 94% of healthy volunteers, with women experiencing more negative effects | Research

The takeaway

After a single 1.19 mg IV dose of THC, 94% of healthy participants experienced at least mild psychotomimetic symptoms, with 31% still affected 2.5 hours later. Women experienced significantly more negative symptoms and all physical reactions.

Researchers studying THC psychotomimetic effects, clinicians prescribing medical cannabis, and anyone interested in sex differences in cannabis response.

94% symptomatic, women more affected

What the researchers found

In the 20 minutes after THC, 94% experienced at least mild symptoms (19% moderate-severe). 31% still had mild symptoms at 2.5 hours. After placebo, 62% had no symptoms at all. Acute physical reactions were 2.5x more frequent with THC (31% vs 12% placebo). Women had more negative symptoms (56-89%) than men (0-29%), and all acute physical reactions occurred exclusively in women.

Why it matters

This controlled study demonstrates that even a very low dose of THC produces near-universal psychotomimetic effects in cannabis-naive individuals, and reveals striking sex differences that have implications for both recreational use and medical dosing.

The numbers in context

16 participants, 7 male. 1.19 mg IV THC. 94% experienced symptoms. 19% moderate-severe. 31% still symptomatic at 2.5 hours. Physical reactions: THC 31% vs placebo 12%. Women: 56-89% negative symptoms vs men 0-29%. Physical reactions: exclusively female.

How the study worked

Double-blind, randomized, placebo-controlled crossover study of IV THC (1.19 mg/2 mL) in 16 healthy participants (7 male) with modest previous cannabis exposure.

What this study cannot tell us

Very small sample (16 participants, 9 female, 7 male). IV administration does not replicate typical use. Single dose study. Participants had modest prior cannabis experience. Cross-over design may introduce order effects.

How to read the evidence

Rated moderate because this is a well-designed RCT crossover study, though the sample is very small.

When this study was published

Published in 2019.

The bigger picture

The sex difference finding is particularly important as cannabis products become more widely available. If women are substantially more vulnerable to negative THC effects, sex-specific dosing guidance may be needed for medical cannabis.

Questions still open

Why do women experience more negative THC effects? Would sex differences persist with chronic use? Should medical cannabis dosing be sex-adjusted?

Common questions

Does THC affect men and women differently?

In this study, women experienced significantly more negative symptoms (56-89% vs 0-29% in men) and all physical reactions after a low THC dose occurred exclusively in women.

How common are psychotic-like symptoms from THC?

At a dose of just 1.19 mg IV, 94% of healthy volunteers experienced at least mild psychotomimetic symptoms, with about 1 in 5 experiencing moderate-to-severe effects.

Read the original research

Descriptive Psychopathology of the Acute Effects of Intravenous Delta-9-Tetrahydrocannabinol Administration in Humans.

Brain sciences, 9(4)

View on PubMed ↗Publisher’s paper ↗

Citation

Colizzi, Marco; Weltens, Nathalie; McGuire, Philip; Van Oudenhove, Lukas; Bhattacharyya, Sagnik. (2019). Descriptive Psychopathology of the Acute Effects of Intravenous Delta-9-Tetrahydrocannabinol Administration in Humans.. Brain sciences, 9(4). https://doi.org/10.3390/brainsci9040093