The endocannabinoid (eCB) system plays a key role in maintaining homeostasis and disruptions in eCB signaling have been linked to obesity, anxiety, and depression. Emerging data suggest that behavioral interventions, such as physical exercise, boosts circulating eCB levels. Indeed, the classic “runner’s high” - the sense of wellbeing and mood elevation felt after exercise - is thought to be due, in part, to increasing eCB levels. We conducted a PubMed search to identify original research articles published prior to 12/31/2020 that examined the impact of exercise on circulating eCB levels. The search yielded 260 articles, and 31 articles were included in the systematic review, while 10 articles were included in the meta-analysis. All 31 studies reported levels of the eCB anandamide (AEA), and of the 49 total samples in the articles, 36 samples found an increase in AEA after exercise. In addition, 42 samples reported on 2-AG; however, the results were inconsistent. The meta-analysis conducted using RevMan software confirms a consistent increase in circulating AEA and 2-AG levels following exercise. Interestingly, variance in blood collection and eCB extraction may be responsible for heterogeneity seen within the meta-analysis, and standardization of collection and processing methods warrants further study.

1. Behind the “Runner’s
High”: A systematic review
and meta-analysis on the
effects of exercise on the
endocannabinoid system
Shreya Desai; Breanna Borg; Hilary Marusak
Department of Psychiatry and Behavioral Neurosciences,
Wayne State University

2. Introduction: What is the endocannabinoid system (ECS)?

3. The “runner’s high” is linked to the
endocannabinoid (eCB) system
Introduction:
Performed systematic review and meta-analysis exploring:
1) if exercise increases/decreases eCB levels and by how
much.
2) how exercise sessions (i.e., single bout of exercise) vs.
programs (i.e., 12-weeks of exercise) may have different
effects on eCB signaling.
3) how effects may also differ based on patient group (e.g.,
healthy volunteers vs. PTSD), or based on species
(animal models vs. humans), exercise modality, intensity,
etc.

4. Methods

5. Results: Anandamide (AEA)
AEA levels increased in 36 of the
49 samples (73%), decreased in 6
samples, and remained unchanged
in 7 samples
AEA: Systematic Review
AEA: Meta-analysis
24 samples included in meta-
analysis

6. AEA levels increased in 17 of the
42 samples (40%), decreased in 2
samples, and remained unchanged
in 23 samples
2-AG: Systematic Review
2-AG: Meta-analysis
23 samples included in meta-
analysis
Results: 2-Arachidonoylglycerol (2-AG)

7. Discussion:
 Consistent increase in AEA levels following exercise
across modalities, species, populations, etc.
- Meta-analysis confirmed this increase, but lots of
heterogeneity in terms of magnitude of effect.
 Increasing the intensity of exercise increased the amount
of AEA circulation in the body.
 Meta-analysis showed a significant increase in 2-AG
following an exercise session, but results were less
consistent.

8. Discussion:
When blood draws were taken and extracted for eCBs is
important to look at:

9. Discussion: future direction
 Exercise-session related increases in 2-AG are less
consistent than AEA.
 Does the increase depend on modality?
 Time frame for recovery (how long does AEA stay
elevated)?
 We need to standardize collection methods &
processing to reduce heterogeneity

10. Thank you to my wonderful mentors Dr. Marusak and Ms. Borg.
Learn more about our research at the THINK lab
Website: www.WSUTHINKlab.com
Instagram: @WSUTHINKlab
QUESTIONS?