THC and CBD had opposing effects on how people read emotions in faces, but evidence is limited | Research

The takeaway

A systematic review of 7 experiments found THC impaired or did not change facial emotion recognition, while CBD improved performance and counteracted THC effects, with opposing brain activation patterns for threatening faces.

Social cognition researchers, psychiatrists treating anxiety/depression, and neuroscientists studying cannabinoid effects on emotion processing.

THC and CBD showed opposing effects on emotion recognition and brain response to threatening faces

What the researchers found

Across 7 experiments (170 total participants), THC (7.5-15 mg) had no effect in 3 experiments and reduced facial emotion recognition in 3 others. CBD had no effect in 2 experiments but improved performance and counteracted THC effects in one. THC (≥10 mg) and CBD (600 mg) showed opposing effects on brain activation, skin conductance, and anxiety when viewing negative/threatening faces.

Why it matters

Impaired emotion recognition is a feature of anxiety and depression. If THC worsens and CBD improves this ability, it provides a mechanistic explanation for why THC can worsen anxiety while CBD may reduce it.

The numbers in context

7 experiments; 170 participants; THC 7.5-15 mg; CBD 600 mg; THC impaired REFE in 3 of 6 experiments; CBD improved in 1 of 3; opposing brain activation for threatening faces.

How the study worked

Systematic review (PROSPERO registered: CRD42019135085) of controlled trials assessing THC and/or CBD effects on recognition of emotions in facial expressions (REFE), searching standard databases.

What this study cannot tell us

Only 7 experiments (very limited data); small total sample (170); heterogeneous THC and CBD doses; mostly acute single-dose studies; REFE tasks vary across studies; limited to healthy volunteers.

How to read the evidence

Moderate: registered systematic review of controlled trials, but very few studies (7 experiments) with small samples.

When this study was published

Published 2020.

The bigger picture

The ability to accurately read emotions is fundamental to social functioning. THC impairing this while CBD improves it aligns with broader patterns: THC disrupts social cognition while CBD may enhance it. This has implications for both recreational and therapeutic use.

Questions still open

Does chronic cannabis use permanently alter emotion recognition? Would CBD pre-treatment prevent THC-induced social cognition impairment?

Common questions

Does cannabis affect how you read emotions?

THC impaired facial emotion recognition in half the experiments reviewed, while CBD improved it in one study and counteracted THC effects. They also showed opposing brain activation patterns when viewing threatening faces.

Why does this matter for anxiety?

Accurately reading emotions is essential for social interaction. THC making people worse at recognizing emotions, especially threatening ones, may contribute to social anxiety and paranoia. CBD improving this recognition could explain its anxiolytic effects.

Read the original research

The effects of Cannabidiol (CBD) and Delta-9-Tetrahydrocannabinol (THC) on the recognition of emotions in facial expressions: A systematic review of randomized controlled trials.

Neuroscience and biobehavioral reviews, 118, 236-246

View on PubMed ↗Publisher’s paper ↗

Citation

Rossi, Giordano Novak; Osório, Flávia L; Morgan, Celia J A; Crippa, José Alexandre S; Bouso, José Carlos; Rocha, Juliana Mendes; Zuardi, Antônio W; Hallak, Jaime E C; Santos, Rafael G Dos. (2020). The effects of Cannabidiol (CBD) and Delta-9-Tetrahydrocannabinol (THC) on the recognition of emotions in facial expressions: A systematic review of randomized controlled trials.. Neuroscience and biobehavioral reviews, 118, 236-246. https://doi.org/10.1016/j.neubiorev.2020.07.034