Psychedelic Science Newsletter
Issue #14December 8, 20257 studies

Meta-analysis of 14 studies shows microdosing may reduce cognitive control—rather than enhance it

This week brought surprising findings about psychedelics and the brain—from ketamine's unexpected effects on thinking to microdosing's cognitive reality check.

🧠 Psychedelic Microdosing Decreases Cognitive Control

  • Meta-analysis of 14 studies with 1,614 participants found microdosing psychedelics significantly decreased cognitive control (executive functions like attention and decision-making)

  • No benefits were detected in other cognitive domains, contradicting popular claims about enhanced mental performance

  • Neither substance type (psilocybin vs LSD), dosage (0.1-0.5g psilocybin; 6.5-20μg LSD), nor duration (1-42 days) changed these effects

Why it matters: This challenges the widespread belief that microdosing enhances cognitive performance, suggesting it may actually impair top-down mental control processes.

🥉 Top 5% journal 🔗 Neuroscience and Biobehavioral Reviews 🗓️ Nov 28

Key Findings

🔬 Ketamine and Lithium Target Different Patient Types

  • Review of 42 studies found ketamine response linked to metabolic risk factors, anxiety, and non-melancholic depression—traits that predict poor lithium response

  • Despite mechanistic overlap in brain pathways (GSK-3β/mTOR), the two treatments appear to help different patient populations

  • 30% of bipolar patients respond to lithium, but no studies directly tested whether ketamine response predicts lithium effectiveness

💡 Could help doctors better match treatments to individual patients with bipolar disorder.
Top 20% journal 🔗 Pharmaceuticals 🗓️ Nov 27

🧪 New Method Reveals Variable Psilocybin Content in Mushrooms

  • Novel nuclear magnetic resonance technique accurately measured psilocybin and psilocin in dried Psilocybe cubensis samples

  • Significant variability found in tryptamine content and psilocybin-to-psilocin ratios among samples, likely influenced by storage conditions

  • Method offers rapid, calibration-free alternative to conventional chromatography for quality control

💡 May improve safety and dosing consistency as psychedelic mushrooms move toward clinical and regulatory approval.
Top 30% journal 🔗 ACS Omega 🗓️ Dec 1

📊 MDMA Enhances Emotional Empathy But Impairs Negative Emotion Recognition

  • Meta-analysis found MDMA increases emotional empathy (feeling others' emotions) but reduces accuracy in recognizing sad, fearful, and angry facial expressions

  • No effects on cognitive empathy (understanding others' emotions) or recognizing happy expressions

  • Findings may inform optimization of MDMA-assisted therapy protocols currently under regulatory review

💡 Suggests MDMA's therapeutic benefits may come from enhanced emotional connection rather than better emotion reading.
Top 20% journal 🔗 Scientific Reports 🗓️ Nov 29

🎯 Childhood Trauma Resurfaces During 42% of Difficult Psychedelic Experiences

  • Survey of 608 people with post-psychedelic difficulties found 41.8% linked their problems to early trauma that emerged during the experience

  • Follow-up interviews with 18 participants revealed 50% had predominantly positive integration, while 22% experienced re-traumatization

  • 39% directly re-experienced trauma, including some with no prior memory of events

💡 Highlights the critical need for trauma-informed approaches and robust support systems in psychedelic therapy.
Top 20% journal 🔗 Scientific Reports 🗓️ Nov 27

⚕️ Limited Evidence for Cannabis in OCD, Stronger Signal for Psilocybin

  • Comprehensive review found little evidence supporting cannabinoids for obsessive-compulsive disorder treatment

  • Stronger research signal emerged for psilocybin in treatment-resistant OCD, though based on limited studies

  • 40-60% of OCD patients don't respond to first-line treatments, creating urgent need for new options

💡 May guide researchers toward more promising psychedelic approaches for treatment-resistant OCD.
🎖️ Top 10% journal 🔗 Journal of Psychiatric Research 🗓️ Nov 29

🧬 Ketamine's Antidepressant Effects Center on Hippocampus

  • Review synthesized evidence showing ketamine enhances hippocampal brain plasticity through multiple pathways including NMDA receptor blockade and BDNF signaling

  • Effects coordinate with broader brain networks, particularly prefrontal cortex and lateral habenula

  • Therapeutic actions appear separate from stress hormone (HPA axis) normalization

💡 Provides a brain circuit-based framework for developing next-generation rapid-acting antidepressants.
🥉 Top 5% journal 🔗 Neuropsychopharmacology 🗓️ Nov 26

Implications

These findings paint a more nuanced picture of psychedelics than popular narratives suggest—microdosing may impair rather than enhance cognition, while therapeutic applications require careful attention to trauma history and individual patient characteristics. The research points toward more personalized, evidence-based approaches to psychedelic medicine.

Studies in this issue

Primary sources used for this newsletter.

  1. How Small Doses of Psychedelics May Affect Thinking Abilities: A Review and Analysis
    main storyNeuroscience and biobehavioral reviews2025-11-28PMID 41314362
  2. Possible benefits of cannabinoids and psychedelics as new treatments for OCD
    key findingJournal of psychiatric research2025-11-29PMID 41317726
  3. Childhood trauma and patterns of change after psychedelic experiences
    key findingScientific reports2025-11-27PMID 41309700
  4. Similarities and Differences in How Ketamine and Lithium Work in Bipolar Disorder
    key findingPharmaceuticals (Basel, Switzerland)2025-11-27PMID 41304907
  5. New NMR Method to Measure Psilocybin and Psilocin Levels in Psychedelic Mushrooms
    key findingACS omega2025-12-01PMID 41322617
  6. MDMA's immediate effects on empathy and recognizing emotions in people: a combined analysis
    key findingScientific reports2025-11-29PMID 41315485
  7. The hippocampus as a key center in ketamine’s antidepressant effects: from molecules to brain circuit changes
    key findingNeuropsychopharmacology : official publication of the American College of Neuropsychopharmacology2025-11-26PMID 41299093

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