A single dose of CBD increased connectivity between frontal cortex and striatum in healthy volunteers | Research

The takeaway

A crossover study in 16 healthy males found that 600mg oral CBD increased fronto-striatal resting-state connectivity compared to placebo, a neural effect that may relate to its potential antipsychotic properties.

Read this if you are interested in how CBD affects brain connectivity and its potential relevance to antipsychotic treatment.

CBD enhanced fronto-striatal connectivity; this circuit is disrupted in psychosis

What the researchers found

Researchers conducted a crossover pharmacological fMRI study giving 16 healthy male volunteers placebo, 10mg oral THC, and 600mg oral CBD in separate sessions, then measuring resting-state brain connectivity.

CBD significantly increased connectivity between frontal cortex regions and the striatum compared to placebo. This fronto-striatal circuit is important for executive functioning, decision making, salience generation, and motivation.

Contrary to expectations, THC did not show significant effects compared to placebo, which the researchers attributed to likely insufficient THC concentration in the brain during scanning (the oral dose may not have peaked in time).

The fronto-striatal connectivity enhanced by CBD is of particular interest because disruptions in this circuit are observed in schizophrenia and other neuropsychiatric conditions, potentially providing a neural correlate for CBD's reported antipsychotic effects.

Why it matters

Understanding how CBD affects brain connectivity in healthy volunteers provides a foundation for understanding its therapeutic potential. The specific enhancement of fronto-striatal connectivity, a circuit disrupted in psychosis, offers a plausible neural mechanism for CBD's antipsychotic effects seen in clinical studies.

The numbers in context

16 healthy males. Three sessions: placebo, 10mg THC, 600mg CBD. CBD increased fronto-striatal connectivity vs. placebo. THC showed no significant effects (likely timing issue). 3T MRI scanner used.

How the study worked

Double-blind, placebo-controlled crossover study. 16 healthy male volunteers received placebo, 10mg oral THC, and 600mg oral CBD across 3 sessions. Resting-state fMRI measured seed-voxel connectivity from caudate and putamen striatal regions. Scanned in a 3T scanner.

What this study cannot tell us

Small sample size (16 males only). THC findings inconclusive due to likely dosing/timing issues. Single-session design cannot capture chronic effects. Resting-state connectivity does not directly measure functional outcomes. Healthy volunteers may respond differently than patients with neuropsychiatric conditions.

How to read the evidence

Small crossover fMRI study in healthy volunteers provides preliminary neuroimaging evidence of CBD's brain effects, requiring replication and clinical population studies.

When this study was published

Published in 2018. Neuroimaging research on CBD's brain effects has expanded considerably since.

The bigger picture

This study contributes to the growing understanding of CBD's effects on brain function. The fronto-striatal circuit is implicated in multiple neuropsychiatric conditions beyond psychosis, including ADHD, addiction, and depression, suggesting CBD's brain connectivity effects could have broad therapeutic relevance.

Questions still open

Does chronic CBD use produce sustained changes in fronto-striatal connectivity? Would patients with schizophrenia show the same CBD-induced connectivity enhancement? What is the dose-response relationship between CBD and fronto-striatal connectivity?

Common questions

What did CBD do to the brain?

CBD increased the connectivity between frontal cortex regions and the striatum during rest. This fronto-striatal circuit handles executive functioning, decision making, and motivation, and is disrupted in conditions like schizophrenia.

Did THC have the opposite effect?

The study expected opposing effects, but THC showed no significant changes compared to placebo, likely because the oral dose had not reached sufficient brain concentration during the scanning window.

Read the original research

Probing the endocannabinoid system in healthy volunteers: Cannabidiol alters fronto-striatal resting-state connectivity.

European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology, 28(7), 841-849

View on PubMed ↗Publisher’s paper ↗

Citation

Grimm, Oliver; Löffler, Martin; Kamping, Sandra; Hartmann, Aljoscha; Rohleder, Cathrin; Leweke, Markus; Flor, Herta. (2018). Probing the endocannabinoid system in healthy volunteers: Cannabidiol alters fronto-striatal resting-state connectivity.. European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology, 28(7), 841-849. https://doi.org/10.1016/j.euroneuro.2018.04.004