How THC and CBD Work Differently in the Brain and Why It Matters | Research

The takeaway

A pharmacology review explained how CBD can reduce some of THC's psychoactive effects, leading to the development of Nabiximols, a THC/CBD combination drug for MS spasticity.

Anyone wanting to understand the basic science behind why THC and CBD produce different effects.

CBD can decrease some of THC's psychosis-like effects

What the researchers found

This review examined the pharmacodynamic interplay between THC and CBD, the two most studied of the 70+ phytocannabinoids in cannabis.

THC directly activates CB1 and CB2 cannabinoid receptors, producing its well-known psychoactive effects. CBD, by contrast, has very low affinity for these receptors and works through other mechanisms. Evidence suggests CBD can decrease some of the psychomimetic (psychosis-like) effects of THC.

This opposing relationship between THC and CBD led to the development of Nabiximols (Sativex), a pharmaceutical spray containing a roughly 1:1 ratio of THC to CBD, approved for moderate to severe spasticity in multiple sclerosis.

Why it matters

Understanding that THC and CBD have opposing effects helps explain why different cannabis strains and products produce different experiences. It also has practical implications for medical cannabis formulation and for understanding why high-THC, low-CBD products may carry greater risk.

The numbers in context

Cannabis contains more than 70 phytocannabinoids. THC and CBD are the two most studied. Nabiximols contains a roughly 1:1 THC:CBD ratio.

How the study worked

This was a pharmacodynamic review published in The Mental Health Clinician, examining the evidence for how THC and CBD interact at the receptor and cellular level.

What this study cannot tell us

The abstract provided limited mechanistic detail. The evidence for CBD reducing THC's effects comes from specific experimental paradigms and may not apply uniformly to all of THC's actions. The optimal ratio of THC to CBD for therapeutic purposes remains unclear.

How to read the evidence

This is a pharmacodynamic review synthesizing evidence on THC-CBD interactions. It provides moderate-quality mechanistic overview.

When this study was published

Published in 2016. Understanding of THC-CBD interactions has continued to develop, particularly with the growing CBD product market.

The bigger picture

The THC-CBD interaction has become one of the most important concepts in cannabis science. As the cannabis market has evolved toward increasingly high-THC products with minimal CBD, this review's emphasis on CBD's moderating role has become even more relevant.

Questions still open

What is the optimal THC:CBD ratio for different medical conditions? Does CBD meaningfully reduce THC's adverse effects when both are consumed together in recreational cannabis?

Common questions

Does CBD cancel out THC's effects?

CBD appears to reduce some of THC's psychomimetic effects but does not completely block THC. The interaction is more nuanced than simple cancellation, and CBD has its own pharmacological actions independent of its relationship to THC.

Why does the THC:CBD ratio matter?

Different ratios produce different overall effects. Products with high THC and little CBD may produce stronger psychoactive effects and potentially more adverse reactions, while balanced THC:CBD products like Nabiximols may offer therapeutic benefits with fewer side effects.

Read the original research

Delta-9-tetrahydrocannabinol and cannabidiol: Separating the chemicals from the "weed," a pharmacodynamic discussion.

The mental health clinician, 6(6), 277-284

View on PubMed ↗Publisher’s paper ↗

Citation

Boggs, Douglas Lee; Peckham, Alyssa; Boggs, Angela A; Ranganathan, Mohini. (2016). Delta-9-tetrahydrocannabinol and cannabidiol: Separating the chemicals from the "weed," a pharmacodynamic discussion.. The mental health clinician, 6(6), 277-284. https://doi.org/10.9740/mhc.2016.11.277