New neuroscience research published in the journal Neuropsychopharmacology reveals that cannabidiol (CBD) does not mitigate the disruptive effects of delta-9-tetrahydrocannabinol (THC) on brain connectivity. Surprisingly, the study suggests that CBD might even exacerbate these effects in some cases. This challenges the widely held belief that CBD can counterbalance the psychoactive impact of THC in cannabis.

Motivation for the Study

The motivation behind this research stems from the increasing use of cannabis among adolescents and young adults, a critical period for brain development. Previous studies indicated that chronic cannabis use during adolescence could lead to changes in brain connectivity and cognitive impairments. However, there was insufficient detailed research on the acute effects of cannabis in this age group, particularly considering different compositions of cannabis with varying levels of THC and CBD.

THC and CBD: A Comparative Overview

• THC: The main psychoactive component responsible for the euphoric “high” and cognitive alterations associated with cannabis use. THC binds directly to cannabinoid receptors in the brain, influencing mood, perception, and cognition.
• CBD: A non-psychoactive compound suggested to have potential therapeutic properties, such as reducing anxiety and possessing anti-inflammatory effects. Unlike THC, CBD interacts more subtly with cannabinoid receptors and can modulate the effects of THC.

Study Design and Participants

The study was part of the larger “CannTeen” project and involved 48 semi-regular cannabis users, divided into two groups:

• Adolescents: 24 participants with a mean age of 17.2 years.
• Adults: 24 participants with a mean age of 27.8 years.

Participants were selected based on their history of cannabis use (0.5 to 3 days per week over the past three months) to match the frequency between the adolescent and adult groups. Recruitment methods included school assemblies, physical posters, flyers, and online advertisements from the Greater London area.

Experimental Procedure

Screening and Drug Administration

Before each of the three sessions, participants were screened for recent drug and alcohol use through saliva and breathalyser tests to ensure no recent consumption. The study used a double-blind, placebo-controlled design involving three drug administration sessions where participants inhaled one of three types of cannabis:

• Placebo: 0 mg THC, 0 mg CBD.
• THC-only: 8 mg THC for a 75 kg person, zero CBD.
• THC + CBD: 8 mg THC and 24 mg CBD for a 75 kg person.

The cannabis was administered using a Volcano Medic Vaporizer to ensure precise dosing and controlled administration.

fMRI Scanning

Approximately 50 minutes after inhalation, participants underwent a resting-state functional magnetic resonance imaging (fMRI) scan to capture the peak effects of the drugs. Resting-state fMRI measures and maps brain activity by detecting changes associated with blood flow while the participant is not performing any specific tasks, allowing researchers to observe natural fluctuations in brain activity and connectivity between different regions.

Key Findings

The study’s findings revealed significant disruptions in brain connectivity across several key networks after cannabis administration:

• Executive Networks
• Salience Networks
• Default Mode Networks

Interestingly, the presence of CBD did not mitigate these disruptions. In some cases, CBD appeared to enhance the disruptive effects of THC on brain connectivity.

This study provides new insights into the effects of THC and CBD on brain connectivity, challenging the notion that CBD can temper the psychoactive effects of THC. These findings underscore the importance of further research to understand the complex interactions between different cannabis compounds and their impact on the brain, particularly during critical developmental periods.

Source: PsyPost