The science

The Library

The practices at Halcyon are old. The research on them is newer, and growing. These are the studies we read and return to, each with a short note in plain language and a link to the original paper. We share them to inform, not to promise, and none of it is medical advice.

6 studies

Nature immersion · Guided Hike

Nature experience reduces rumination and subgenual prefrontal cortex activation

Bratman GN, Hamilton JP, Hahn KS, et al.

Proceedings of the National Academy of Sciences · 2015

Rumination, the habit of repetitive negative thinking about oneself, is linked to higher risk of depression. In this study published in PNAS, healthy participants took a 90-minute walk either in a natural setting or in an urban setting. Those who walked in nature showed reduced self-reported rumination and reduced activity in the subgenual prefrontal cortex, a brain area associated with rumination, as measured by brain imaging. Those who walked along a busy urban route showed no such changes. The authors suggest this may be one pathway by which nature experience supports mental well-being, and that accessible natural areas could be an important mental health resource. One limitation is that the abstract does not report a large sample, and the participants were healthy adults, so the effect in people with depression is not tested here.

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Meditation · Consciousness

Mindfulness practice leads to increases in regional brain gray matter density

Hölzel BK, Carmody J, Vangel M, et al.

Psychiatry Research: Neuroimaging · 2011

This study from the Lazar lab at Massachusetts General Hospital used MRI brain scans to look for structural changes after an eight-week mindfulness-based stress reduction (MBSR) program. Sixteen healthy adults who had never meditated were scanned before and after the course and compared with 17 people on a waiting list. The MBSR group showed increases in gray matter concentration in the left hippocampus, an area involved in learning and memory, and in the posterior cingulate cortex, the temporo-parietal junction and the cerebellum. These regions are associated with emotion regulation, self-referential thinking and perspective taking. The authors suggest that taking part in MBSR is associated with measurable changes in brain structure. The obvious limitation is size: with about 33 people in total and no randomization described in the abstract, the findings are best seen as early and in need of replication.

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Breathwork · Consciousness

How Breath-Control Can Change Your Life: A Systematic Review on Psycho-Physiological Correlates of Slow Breathing

Zaccaro A, Piarulli A, Laurino M, et al.

Frontiers in Human Neuroscience · 2018

This systematic review asked what actually happens in the body and brain when healthy people slow their breathing to fewer than ten breaths per minute. From 2,461 abstracts, 15 studies met the criteria. Across them, slow breathing was linked with higher heart rate variability, a marker of parasympathetic (rest and digest) activity, along with shifts in brain activity such as more alpha and less theta power on EEG. People also reported feeling more comfortable, relaxed, pleasant, vigorous and alert, with less anxiety, anger and confusion. The authors propose two possible mechanisms, one involving awareness of internal body states and one involving nasal breathing and the olfactory system. A clear limitation is the small evidence base: only 15 studies qualified, and the brain imaging findings rest on a single fMRI study.

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Psychedelic Assisted Psychotherapy · Consciousness

Human hallucinogen research: guidelines for safety

Johnson MW, Richards WA, Griffiths RR

Journal of Psychopharmacology · 2008

This paper from Johns Hopkins reviews the history of human research with classic psychedelics, the risks involved, and how researchers can reduce them. It is a review and set of guidelines rather than a trial. The authors note that while these substances carry relatively low physical risk and are not considered drugs of dependence, they carry unique psychological risks. The most likely is overwhelming distress during the session, and rarer risks include prolonged psychotic reactions. Recommended protections include screening out people with a personal or family history of psychotic or other severe psychiatric disorders, building trust before the session, careful preparation, a supportive physical setting, and at least two monitors present. A limitation is that these guidelines were written for research settings rather than everyday clinical practice.

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Psychedelic Assisted Psychotherapy · Consciousness

Rapid and sustained symptom reduction following psilocybin treatment for anxiety and depression in patients with life-threatening cancer: a randomized controlled trial

Ross S, Bossis A, Guss J, et al.

Journal of Psychopharmacology · 2016

This NYU trial, published alongside a similar Johns Hopkins study, examined a single moderate dose of psilocybin given with psychotherapy for anxiety and depression linked to cancer. Twenty-nine patients were randomly assigned in a double-blind crossover design to psilocybin or niacin, an active placebo, with therapy in both conditions. In this study, psilocybin was followed by rapid and lasting reductions in anxiety and depression, less demoralization and hopelessness, and better spiritual wellbeing and quality of life. At about six and a half months, roughly 60 to 80% of participants still had clinically significant reductions. As in the companion study, the intensity of the mystical experience was linked to the benefit. The small sample is an important limitation. Psilocybin remains a Schedule I substance under US federal law, and regulated access currently exists only through state programs in Oregon and Colorado; it is not available in New Jersey.

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Psychedelic Assisted Psychotherapy · Consciousness

Psilocybin produces substantial and sustained decreases in depression and anxiety in patients with life-threatening cancer: A randomized double-blind trial

Griffiths RR, Johnson MW, Carducci MA, et al.

Journal of Psychopharmacology · 2016

This Johns Hopkins trial studied psilocybin in 51 people with life-threatening cancer who also had symptoms of depression and anxiety. Using a randomized, double-blind crossover design, each person received a very low, placebo-like dose and a high dose about five weeks apart, with preparation and support from staff. In this study, the high dose was followed by large decreases in depressed mood and anxiety, along with gains in quality of life, sense of meaning and optimism, and less fear of death. About 80% still showed clinically significant improvement at six months, and the strength of a mystical-type experience during the session was linked to the benefits. A limitation is that blinding is hard with psilocybin, since participants can often tell which dose they received. Psilocybin remains a Schedule I substance under US federal law, and regulated access currently exists only through state programs in Oregon and Colorado; it is not available in New Jersey.

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