The effect of methamphetamine and 3,4-methylenedioxymethamphetamine on peripheral endocannabinoid concentrations: a study in healthy adults

Mayo and colleagues situate this study within a broader effort to understand how stimulant drugs affect neurobiological systems involved in stress, reward and substance use disorders. The endocannabinoid (eCB) system — comprising CB1/CB2 receptors and the endogenous ligands anandamide (AEA) and 2-arachidonoylglycerol (2-AG) — is implicated in emotion regulation, reward processing and HPA-axis stress responsivity, and preclinical data suggest interactions between stimulants and eCB signalling. Human data are limited and mixed: chronic stimulant users show altered peripheral eCB profiles, but acute effects of prototypical stimulants on circulating AEA and 2-AG have not been well characterised in healthy participants. The present study aimed to test whether acute administration of methamphetamine (MA) and 3,4-methylenedioxymethamphetamine (MDMA) differentially alter peripheral eCB concentrations in healthy adults. Based on prior findings and mechanistic differences between the drugs, the investigators hypothesised that MA would increase 2-AG concentrations, whereas MDMA would not affect eCB levels. The study also measured cortisol, brain-derived neurotrophic factor (BDNF), physiological responses and subjective drug effects to relate any eCB changes to stress and subjective experience.

This was a within-subject, double-blind experiment in which each participant attended three counterbalanced four-hour sessions and received oral capsules containing MA (20 mg), MDMA (100 mg) or placebo. Sessions were separated by at least four days (mean 13.46 days). Blood draws for biochemical assays were taken once per session between 150 and 180 minutes after capsule ingestion, a time chosen to capture peak drug effects. Subjective and physiological measures (heart rate, blood pressure) were collected at baseline and at 1, 1.5, 3 and 4 hours post-dose. Participants completed the Drug Effects Questionnaire (DEQ), visual analogue scales (VAS) targeting prosocial feelings, and a Session End Questionnaire including allocation guesses. Healthy adults aged 18–35 were recruited (N = 25). Eligibility required at least high school education, BMI 18–26, good health, fluency in English and at least one prior experience with MDMA or a psychedelic without a prior bad reaction. Exclusion criteria included prescription medication use and history of cardiac disease or high blood pressure; women not on oral contraceptives were tested only in the follicular phase. Participants were asked to abstain from drugs for seven days, alcohol for 24 hours and caffeine on session days. Three participants were unable to complete blood draws, yielding 22 participants for the endocannabinoid analyses. Plasma AEA and 2-AG were quantified by liquid chromatography–mass spectrometry following protein precipitation and lipid extraction with internal standards. Cortisol and BDNF were measured by ELISA. Statistical analyses used repeated-measures ANOVA with session (placebo, MA, MDMA) and time (five levels for subjective/physiological measures) as within-subject factors. eCB, cortisol and BDNF comparisons used repeated-measures ANOVAs; cortisol and BDNF data were winsorized at the 5th and 95th percentiles to limit outlier influence. Post-hoc paired t-tests were used as appropriate, and multiple comparisons were corrected using the Benjamini–Hochberg procedure. Spearman correlations tested relationships among eCBs, cortisol, BDNF and subjective ratings.

Demographics and dataset: The analysed sample comprised 25 enrolled participants (17 men, 8 women; mean age 27.4 years), with 22 participants included in the plasma eCB analyses due to three incomplete blood draws. Participants reported an average of 7.1 prior MDMA exposures and none were cigarette smokers. Physiological effects: Both MA and MDMA increased heart rate relative to placebo. Repeated-measures ANOVA showed a main effect of drug on heart rate (F(2,42) = 5.468, p = 0.008, η2 = 0.207), time (F(4,84) = 18.796, p < 0.001, η2 = 0.472) and a drug × time interaction (F(8,168) = 5.072, p < 0.001, η2 = 0.195). Post-hoc comparisons indicated higher heart rate in the MDMA condition versus placebo at 1.5 h (t(21) = 3.080, pcor = 0.02), 3 h (t(21) = 4.943, pcor = 0.005) and 4 h (t(21) = 3.163, pcor = 0.02). MA increased heart rate versus placebo at 3 h (t(21) = -4.024, pcor = 0.005) and 4 h (t(21) = -3.748, pcor = 0.005). Blood pressure data were reported in supplemental materials. Subjective effects: Both stimulants elevated ratings on the DEQ and VAS compared with placebo. For 'feeling drug effects' there was a main effect of drug (F(2,48) = 22.613, p < 0.001, η2 = 0.485), time (F(4,96) = 51.913, p < 0.001, η2 = 0.684) and a time × drug interaction (F(8,192) = 8.871, p < 0.001, η2 = 0.270). MDMA increased ratings of feeling drug effects at 1, 1.5, 3 and 4 h versus placebo; MA produced a significant increase at 4 h. Ratings of 'feeling high' also showed strong drug effects (F(2,48) = 37.416, p < 0.001, η2 = 0.609) with MDMA producing earlier and larger increases than MA (MDMA > MA at 1.5, 3 and 4 h). VAS ratings of sociability showed a main drug effect (F(2,48) = 7.218, p = 0.002, η2 = 0.247); MA increased sociability at 1.5 and 3 h, while MDMA increased sociability only at 3 h. Ratings of feeling friendly also differed by drug (F(2,48) = 3.369, p = 0.043, η2 = 0.123), with both drugs showing increases at some time points. Endocannabinoids: MA significantly decreased plasma 2-AG relative to placebo (F(1,21) = 4.508, p = 0.046, η2 = 0.177). No significant difference in 2-AG was observed between MDMA and placebo, and no significant effects on AEA were detected in any condition. Correlational analyses at the 3 h timepoint found that, in the placebo session only, higher AEA concentrations correlated with greater ratings of disliking the drug effects (Spearman rs(20) = 0.649, pcor = 0.005). No other significant correlations between eCBs and subjective measures were reported. Cortisol and BDNF: Both MA and MDMA raised plasma cortisol versus placebo (MA: F(1,21) = 8.272, p = 0.009, η2 = 0.283; MDMA: F(1,21) = 18.493, p < 0.001, η2 = 0.468). There were no significant drug effects on BDNF concentrations (p = 0.314). Cortisol did not correlate significantly with eCBs or subjective effects. Summary statistics and further correlation matrices were provided in supplemental materials. Blinding: Participants correctly guessed session allocation on 45.3% of sessions overall; correct identification rates were 64% for placebo, 52% for MDMA and 20% for MA. In 16% of MA sessions participants guessed they had received placebo.

Mayo and colleagues interpret their principal finding as evidence that a single oral dose of methamphetamine acutely lowers peripheral 2-AG concentrations in healthy adults, whereas MDMA at the tested dose does not alter 2-AG or AEA. The decrease in 2-AG after MA contrasts with reports from chronic stimulant users that show elevated 2-AG, leading the authors to propose that eCB responses may differ between acute and chronic exposure, possibly reflecting compensatory adaptations with repeated drug use. They note that preclinical data are mixed — some rodent studies report increases in 2-AG after psychostimulants, others decreases — and that MA's stronger dopaminergic action versus MDMA's relatively greater serotonergic profile could explain the differential effect on 2-AG. The investigators also highlight that both drugs increased cortisol but not BDNF, and that peripheral AEA was positively associated with ratings of disliking the drug experience in the placebo condition, which the authors suggest might reflect expectancy or disappointment when effects are absent. Subjective measures showed that MDMA produced earlier and larger increases in 'feeling high' than MA, while measures of sociability and friendliness showed mixed timing effects across agents; the authors caution that contextual factors and timing may influence prosocial ratings. Several limitations acknowledged by the authors temper interpretation. Plasma eCBs are peripheral markers and may not reflect brain concentrations; a single sampling timepoint per session prevents characterisation of temporal dynamics, and factors such as food, stress and exercise can influence eCB levels. The study did not collect detailed histories of stimulant or other drug use beyond lifetime MDMA exposures, and the seven-day abstinence period may not eliminate longer-term effects of prior substance use. Finally, some physiological and biochemical measures reported in figures or supplements were not fully described in the main text. The authors conclude that their findings provide a novel human demonstration of acute stimulant–endocannabinoid interaction and recommend future studies with multiple sampling timepoints, larger abstinence windows, and consideration of chronic use histories to clarify how acute and repeated stimulant exposure shape eCB signalling and whether cannabinoid-based interventions merit further exploration for stimulant use disorders.