CB1 receptors were 20% elevated in the prefrontal cortex of people who died with major depression | Research

The takeaway

Postmortem analysis found CB1 cannabinoid receptors were upregulated by 20% in the prefrontal cortex of individuals with major depressive disorder, while CB2 receptors were unchanged and mTOR activity was increased by 29%.

Depression neuroscientists, endocannabinoid researchers, and psychiatrists interested in cannabinoid mechanisms in mood disorders.

CB1 receptors +20% in MDD prefrontal cortex; mTOR +29%

What the researchers found

In postmortem prefrontal cortex (BA9) of 23 MDD subjects versus 19 controls, CB1 receptor density was increased by 20% (p=0.02). This upregulation was significant in antidepressant-treated subjects (+23%, p=0.02) but not in antidepressant-free subjects (+14%, p=0.34). CB2 receptor density was unchanged. mTOR activity was increased by 29% (p=0.002) in both antidepressant-treated and untreated MDD subjects. JNK1/2 activity and neuroplastic proteins (PSD-95, Arc, spinophilin) were unchanged.

Why it matters

This provides direct human brain evidence that the endocannabinoid system is altered in depression. The CB1 upregulation may represent a compensatory response to reduced endocannabinoid tone, offering a biological rationale for cannabinoid-based antidepressant strategies.

The numbers in context

23 MDD subjects; 19 controls; CB1 +20% (p=0.02); CB2 unchanged; mTOR +29% (p=0.002); AD-treated CB1 +23% (p=0.02); AD-free CB1 +14% (p=0.34, NS).

How the study worked

Immunoblotting quantification of CB1, CB2, mTOR, JNK1/2, and neuroplastic proteins in postmortem prefrontal cortex from 23 MDD subjects (suicide victims) and 19 matched controls.

What this study cannot tell us

Postmortem tissue (cannot establish causation or temporal sequence); all MDD subjects were suicide victims (may not represent all depression); antidepressant treatment confounds interpretation; relatively small sample; cannot determine if CB1 changes cause or result from depression.

How to read the evidence

Moderate: direct human brain tissue with appropriate controls, but postmortem, cross-sectional, and limited to suicide victims.

When this study was published

Published 2020.

The bigger picture

CB1 upregulation in depression could reflect the brain compensating for insufficient endocannabinoid signaling. If endocannabinoid deficiency contributes to depression, therapies that boost endocannabinoid levels (like FAAH inhibitors) might address this directly.

Questions still open

Is CB1 upregulation a cause or consequence of depression? Would drugs that enhance endocannabinoid tone normalize CB1 levels and improve symptoms?

Common questions

Is the endocannabinoid system changed in depression?

Yes. This study found CB1 cannabinoid receptors were 20% elevated in the prefrontal cortex of people with major depression. This may reflect the brain compensating for reduced endocannabinoid signaling.

Could this explain why cannabis affects mood?

Potentially. If depression involves CB1 receptor upregulation (possibly compensating for low endocannabinoid levels), then cannabis or cannabinoid drugs that activate these receptors might temporarily restore the signaling deficit.

Read the original research

Regulation of cannabinoid CB1 and CB2 receptors, neuroprotective mTOR and pro-apoptotic JNK1/2 kinases in postmortem prefrontal cortex of subjects with major depressive disorder.

Journal of affective disorders, 276, 626-635

View on PubMed ↗Publisher’s paper ↗

Citation

Salort, Glòria; Hernández-Hernández, Elena; García-Fuster, M Julia; García-Sevilla, Jesús A. (2020). Regulation of cannabinoid CB1 and CB2 receptors, neuroprotective mTOR and pro-apoptotic JNK1/2 kinases in postmortem prefrontal cortex of subjects with major depressive disorder.. Journal of affective disorders, 276, 626-635. https://doi.org/10.1016/j.jad.2020.07.074