A single low dose of IV THC caused symptoms in 94% of healthy volunteers, with women experiencing more negative effects
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.
Quick Facts
What This Study 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.
Key Numbers
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 They Did This
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.
Why This Research 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 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.
What This Study Doesn't 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.
Questions This Raises
- ?Why do women experience more negative THC effects?
- ?Would sex differences persist with chronic use?
- ?Should medical cannabis dosing be sex-adjusted?
Trust & Context
- Key Stat:
- 94% symptomatic, women more affected
- Evidence Grade:
- Rated moderate because this is a well-designed RCT crossover study, though the sample is very small.
- Study Age:
- Published in 2019.
- Original Title:
- Descriptive Psychopathology of the Acute Effects of Intravenous Delta-9-Tetrahydrocannabinol Administration in Humans.
- Published In:
- Brain sciences, 9(4) (2019)
- Authors:
- Colizzi, Marco(10), Weltens, Nathalie, McGuire, Philip(21), Van Oudenhove, Lukas, Bhattacharyya, Sagnik
- Database ID:
- RTHC-01992
Evidence Hierarchy
Participants are randomly assigned to treatment or placebo groups to test cause and effect.
What do these levels mean? →Frequently Asked 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.
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Cite This Study
https://rethinkthc.com/research/RTHC-01992APA
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
MLA
Colizzi, Marco, et al. "Descriptive Psychopathology of the Acute Effects of Intravenous Delta-9-Tetrahydrocannabinol Administration in Humans.." Brain sciences, 2019. https://doi.org/10.3390/brainsci9040093
RethinkTHC
RethinkTHC Research Database. "Descriptive Psychopathology of the Acute Effects of Intraven..." RTHC-01992. Retrieved from https://rethinkthc.com/research/colizzi-2019-descriptive-psychopathology-of-the
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.