May 2026
Serotonin
What May 2026's 11 new studies found, synthesized from the papers below. All Serotonin research →
The synthesis
Synthesized from 11 studies in the library · AI-generated, grounded in the abstracts below
Found by searching the library for Serotonin, 5-HT, serotonergic, 5-HT2A receptor, then ranked by relevance.
Research in May 2026 shows that serotonin receptor subtypes (5-HT1A, 5-HT1B, 5-HT2A, 5-HT2B, 5-HT2C, SERT) mediate diverse effects of psychedelics and related compounds, including modulation of subjective experience, compulsive behavior, and anxiety-like effects. Evidence is mixed: some studies find consistent anxiolytic-like effects of serotonergic psychedelics in animal models, while others report anxiogenic or null effects. A key caveat is that most findings come from preclinical or small human studies, with limited data on long-term safety and clinical translation.
Evidence by study
Direction is which way each study's own result points, not our rating of the study.
What the directions mean
- Supports:
- the study found the intervention worked, or its hypothesis held.
- Opposes:
- it found the opposite, no benefit or a harm.
- No effect:
- no significant difference either way.
- Mixed:
- effects in both directions within the same study.
- Unclear:
- the abstract does not report a direction.
| Study | Design | Sample size | Direction | Finding |
|---|---|---|---|---|
| Inhibition of compulsive behavior by dextromethorphan on schedule-induced polydipsia in rats: Role of NMDA, sigma-1, and 5-HT receptors. 2026 | preclinical (animal model) | Supports | Dextromethorphan dose-dependently reduced compulsive-like drinking in rats, and this effect was not reversed by 5-HT2A, NMDA, or sigma-1 antagonists. | |
| A systematic review of the pharmacokinetics of classical serotonergic psychedelic compounds in healthy adult subjects. 2026 | systematic review | 32 | Unclear | Pharmacokinetic profiles of LSD, psilocybin, DMT, mescaline, and 5-MEO-DMT vary significantly; dose-proportional Cmax for LSD and psilocybin, and differences between oral and IV DMT formulations. |
| A spatiotemporal gating hypothesis for psilocybin plasticity: reconciling the 5-HT₂A-TrkB mechanistic paradox. 2026 | theoretical | Unclear | Proposes a spatiotemporal gating hypothesis to reconcile the 5-HT2A-TrkB mechanistic paradox for psilocybin plasticity. | |
| The Serotonin 2B (5‐ HT2B ) Receptor: A Narrative Review of Preclinical and Clinical Evidence on the Safety Considerations and Therapeutic Potential for the Treatment of Depression 2026 | narrative review | Mixed | Peripheral 5-HT2B agonism is linked to valvular heart disease risk, while central 5-HT2B signaling may have antidepressant potential; classical psychedelics bind 5-HT2B but cumulative exposure risks are insufficiently characterized. | |
| Serotonin Transporter Blockade Reduces the Psychedelic-Like Effects of 4-Methoxy- N -methyl- N -isopropyltryptamine and Related Analogs 2026 | preclinical (animal model) | Supports | SERT blockade reduces psychedelic-like effects (head twitch response) of 4-MeO-MiPT and related tryptamine analogs, supporting the hypothesis that SERT inhibition blunts 5-HT2A-mediated effects. | |
| Serotonergic Psychedelics as a Potential Therapeutic Strategy for Anxiety, A Systematic Review 2026 | systematic review | 18 | Mixed | Serotonergic psychedelics (psilocybin, DOI) show anxiolytic-like effects in some behavioral tests, but anxiogenic and null effects are also reported. |
| N -Benzyl-Tryptamine Derivatives as Serotonin 5-HT 2 Receptor Ligands: Synthesis and Structure-Affinity/Activity Relationships 2026 | preclinical (in vitro) | Unclear | N-benzyltryptamine derivatives show structure-activity relationships at 5-HT2 receptors, with meta-substitution favorable and para-substitution unfavorable for affinity. | |
| Psilocybin in Older Adults: Therapeutic Opportunities in Inflammation-Driven Disorders of Aging-From Depression to Neurodegeneration. 2026 | review | Supports | Psilocybin shows potential for inflammation-driven disorders of aging (depression, neurodegeneration) via 5-HT2A, TrkB/BDNF, and neuroimmune modulation, with favorable pharmacokinetics for geriatric use. | |
| 5-HT1A receptor blockade potentiates the subjective effects of DMT. 2026 | RCT (within-subjects, double-blind, placebo-controlled) | 12 | Supports | 5-HT1A receptor blockade with pindolol potentiated DMT-induced subjective effects with a moderate effect size (M=0.514), suggesting 5-HT1A modulates psychedelic subjective effects. |
| The serotonin 1B receptor is required for some of the behavioral effects of psilocybin in mice. 2026 | preclinical (animal model) | Supports | 5-HT1B receptor is required for some behavioral effects of psilocybin (hypolocomotion, persisting effects on anhedonia and anxiety), but not for the acute head twitch response. | |
| B48-13 Severe Serotonin Syndrome With Acute Respiratory Failure Following Ayahuasca and Dextromethorphan Use: A Case Report 2026 | case report | 1 | Opposes | Severe serotonin syndrome with acute respiratory failure occurred after ayahuasca (MAOI) and dextromethorphan use, highlighting serotonergic toxicity risk. |
Dextromethorphan dose-dependently reduced compulsive-like drinking in rats, and this effect was not reversed by 5-HT2A, NMDA, or sigma-1 antagonists.
preclinical (animal model)
Pharmacokinetic profiles of LSD, psilocybin, DMT, mescaline, and 5-MEO-DMT vary significantly; dose-proportional Cmax for LSD and psilocybin, and differences between oral and IV DMT formulations.
systematic review Sample size: 32
Proposes a spatiotemporal gating hypothesis to reconcile the 5-HT2A-TrkB mechanistic paradox for psilocybin plasticity.
theoretical
Peripheral 5-HT2B agonism is linked to valvular heart disease risk, while central 5-HT2B signaling may have antidepressant potential; classical psychedelics bind 5-HT2B but cumulative exposure risks are insufficiently characterized.
narrative review
SERT blockade reduces psychedelic-like effects (head twitch response) of 4-MeO-MiPT and related tryptamine analogs, supporting the hypothesis that SERT inhibition blunts 5-HT2A-mediated effects.
preclinical (animal model)
Serotonergic psychedelics (psilocybin, DOI) show anxiolytic-like effects in some behavioral tests, but anxiogenic and null effects are also reported.
systematic review Sample size: 18
N-benzyltryptamine derivatives show structure-activity relationships at 5-HT2 receptors, with meta-substitution favorable and para-substitution unfavorable for affinity.
preclinical (in vitro)
Psilocybin shows potential for inflammation-driven disorders of aging (depression, neurodegeneration) via 5-HT2A, TrkB/BDNF, and neuroimmune modulation, with favorable pharmacokinetics for geriatric use.
review
5-HT1A receptor blockade with pindolol potentiated DMT-induced subjective effects with a moderate effect size (M=0.514), suggesting 5-HT1A modulates psychedelic subjective effects.
RCT (within-subjects, double-blind, placebo-controlled) Sample size: 12
5-HT1B receptor is required for some behavioral effects of psilocybin (hypolocomotion, persisting effects on anhedonia and anxiety), but not for the acute head twitch response.
preclinical (animal model)
Severe serotonin syndrome with acute respiratory failure occurred after ayahuasca (MAOI) and dextromethorphan use, highlighting serotonergic toxicity risk.
case report Sample size: 1
Points of agreement
- Multiple studies implicate 5-HT2A receptor agonism as a key mechanism for psychedelic effects, but other receptors (5-HT1A, 5-HT1B, 5-HT2B, SERT) modulate these effects.
- Preclinical models consistently show that serotonergic psychedelics can reduce compulsive behavior and anxiety-like behavior, though with variability.
- Pharmacokinetic and safety reviews highlight the importance of receptor selectivity and dosing to avoid adverse effects (e.g., valvulopathy, serotonin syndrome).
Conflicts
- The systematic review on anxiety (article 29292) reports both anxiolytic and anxiogenic/null effects, indicating inconsistency across animal models.
- The role of 5-HT2B in depression is debated: peripheral agonism is harmful (valvulopathy), but central signaling may be beneficial (article 34357).
- SERT blockade reduces psychedelic-like effects in mice (article 28021), but dextromethorphan (a SERT inhibitor) reduces compulsive behavior in rats (article 28760), suggesting context-dependent effects.
Gaps
- Most evidence is preclinical; human studies are limited in size (e.g., n=12) and often lack long-term follow-up.
- Cumulative exposure risks for psychedelics at 5-HT2B receptors are insufficiently characterized (article 34357).
- Durability of anxiolytic and antidepressant effects in older adults (article 27766) and other populations is not established.
- Interactions between psychedelics and other serotonergic agents (e.g., dextromethorphan, MAOIs) are understudied, with only case reports available (article 28214).