Female rats showed biphasic anxiety responses to THC (low dose calming, high dose anxiogenic) that males didn't, and CBD prevented the high-dose anxiety while enhancing the low-dose calm.
Women using cannabis for anxiety, or researchers studying sex differences in cannabinoid pharmacology.
What the researchers found
This study revealed a striking sex difference that most cannabis research has missed by testing only males. Low-dose THC (0.075-0.1 mg/kg) produced clear anxiolytic effects in female rats on the elevated plus-maze. At higher doses (1.0 mg/kg), the effect flipped to anxiogenic. Male rats showed no anxiety changes across the same dose range.
CBD entered the picture as a modulator. Co-administering CBD (1.0 or 3.0 mg/kg) with the anxiogenic THC dose prevented the anxiety response. At the lower CBD dose, it actually enhanced the anxiolytic effect of low-dose THC — making a calming dose even calmer. CBD alone at 3.0 mg/kg was anxiolytic on its own.
The neurochemistry matched the behavior. The anxiogenic THC dose increased dopamine in the medial prefrontal cortex and nucleus accumbens — regions linked to anxiety and salience processing. The anxiolytic dose did not produce these dopamine increases. CBD appeared to work by preventing THC's dopamine-elevating effects in these regions.
Why it matters
Women report higher rates of anxiety disorders and are increasingly using cannabis to manage anxiety. Yet almost all preclinical cannabis-anxiety research has been done in male animals. This study showed the anxiety response to THC is fundamentally different in females — more sensitive at both ends. Low doses helped more, high doses hurt more, and CBD modulated the response.
For women using cannabis for anxiety, this suggests the dose-response window is narrower and the consequences of getting it wrong (too much THC → increased anxiety) are more pronounced. It also provides preclinical support for THC:CBD combinations as potentially superior to THC alone for anxiety management.
The numbers in context
• Anxiolytic THC dose in females: 0.075-0.1 mg/kg
• Anxiogenic THC dose in females: 1.0 mg/kg
• Males: no anxiety changes at any dose tested
• CBD (1.0-3.0 mg/kg) prevented THC-induced anxiety
• Low CBD + low THC: enhanced anxiolytic effect beyond either alone
How the study worked
Naturally cycling female and male Sprague-Dawley rats tested on the elevated plus-maze (standard anxiety test). THC administered at 0.075, 0.1, and 1.0 mg/kg. CBD at 1.0 and 3.0 mg/kg, alone or combined with THC. Dopamine levels measured in medial prefrontal cortex and nucleus accumbens via microdialysis.
Who was studied
Naturally cycling female Wistar rats were tested in the elevated plus-maze.
What this study cannot tell us
Rat model — anxiety in rodents is measured behaviorally and may not correspond to human subjective anxiety. Naturally cycling females were used without tracking estrous cycle stage, which may affect results. The dose range was narrow and the THC amounts were low relative to human recreational use. Acute administration only; chronic effects not studied.
How to read the evidence
Controlled animal study with neurochemical confirmation. Clean dose-response data but limited to rats and acute dosing.
When this study was published
Published in 2021. Sex-specific cannabis research is a growing but still underdeveloped field.
The bigger picture
This study joins RTHC-00051 (sex differences in CB1 receptors) in building the case that cannabis pharmacology is sex-dependent at a fundamental level. The anxiety dimension is particularly important because anxiety is both the most common reason people use cannabis medicinally and the most common adverse effect of using too much. Understanding that females have a different dose-response curve for anxiety could change clinical dosing recommendations.
Replication
Not stated in abstract.
Funding
Not reported in abstract.
Conflicts of interest
Not reported in abstract.
Questions still open
- Do women need lower THC doses than men for anxiolytic effects?
- Would THC:CBD combination products specifically benefit women with anxiety?
- Does the estrous cycle stage affect the anxiety response to cannabis?
Common questions
Does cannabis help or cause anxiety?
Does CBD help with THC-caused anxiety?
Read the original research
Female but not male rats show biphasic effects of low doses of Δ9-tetrahydrocannabinol on anxiety: can cannabidiol interfere with these effects?
Neuropharmacology, 196, 108684
Neuropharmacology is a reputable journal that publishes research on the effects of drugs on the nervous system.
Citation
Salviato, Beatriz Zanutto; Raymundi, Ana Maria; Rodrigues da Silva, Thiago; Salemme, Bruna Wuilleumier; Batista Sohn, Jeferson Machado; Araújo, Fabiano Soares; Guimarães, Francisco Silveira; Bertoglio, Leandro José; Stern, Cristina Aparecida. (2021). Female but not male rats show biphasic effects of low doses of Δ9-tetrahydrocannabinol on anxiety: can cannabidiol interfere with these effects?. Neuropharmacology, 196, 108684. https://doi.org/10.1016/j.neuropharm.2021.108684
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