Select Foundational Sources

Select Foundational Sources on the Science of Hormetic Stress. If you’re going to read one paper, it’s this one (It’s comprehensive and also surprisingly readable): “The hormesis principle of neuroplasticity and neuroprotection” (Mattson and Leak, 2024). It covers history, scientific foundations, and specific studies on hormesis — touching not only on neuroplasticity but autophagy and other processes induced by exertion, heat, fasting and more.  

For the layperson, Sharon Horesh Bergquist’s The Stress Paradox: Why You Need Stress to Live Longer, Healthier, and Happier (2025) is an excellent translator of large scientific concepts into everyday health. And Mark Mattson’s forthcoming book, Challenge. Recover. Repeat. will offer a more scientific lens.

Additional sources key to this book’s content: This broad umbrella paper reviews thousands of studies to show how hormesis triggers biological change: “Hormesis provides a generalized quantitative estimate of biological plasticity” (Calabrese and Mattson, 2011). And these papers each add fundamental learnings: “The catabolic–anabolic cycling hormesis (CACH) model of health and resilience” (Calabrese and Mattson, 2024); “Intermittent metabolic switching, neuroplasticity and brain health” (Mattson et al, 2018); How does hormesis impact biology, toxicology, and medicine? (Calabrese & Mattson, 2017); The Beneficial and Adverse Effects of Autophagic Response to Caloric Restriction and Fasting” (Shabkhizan et al., 2023). Also, this early foundational paper: “Defining hormesis” (Calabrese & Baldwin, 2002).

Select Foundational Sources on the Cultural History of the Coming of Age Ritual. To build and share an understanding of these rituals, I drew on both the classic texts in Western anthropology and ethnography, and also many published writings from Indigenous scholars and writers, who offered us a glimpse of their worldview. The Western accounts are by their nature limited by the shape of the Western mind, and the earlier they’re written, the more they fall prey to regrettable bias. The Indigenous accounts are authentic and written on their own terms; they tend not to focus on the moment of “initiation,” as it’s often called.

From Western anthropology:  Joseph Campbell’s Primitive Mythology / The Masks of God, and The Hero With A Thousand Faces; from Arnold Van Gennep, The Rites of Passage: A classic study of cultural celebrations. From Mircea Eliade, Rites and Symbols of Initiation: The Mysteries of Birth and Rebirth. From Victor Turner, The Forest of Symbols: Aspects of Ndembu Ritual and The Ritual Process; from Margaret Mead, Coming of Age in Samoa and Sex and Temperament; from F.F. Latta, Handbook of Yokuts Indians.

From Indigenous Scholars: See Foundational Sources for Indigenous Scholarship in the Introduction.

Foundational Sources on the Cultural History of Pilgrimage. In addition to the books listed under Foundational Sources for Indigenous Scholarship in the Introduction — these works anchored the book: Victor Turner and Edith Turner’s Image and Pilgrimage in Christian Culture; Mircea Eliade’s The Sacred and the Profane; Diana L. Eck’s India: A Sacred Geography; Jim Leary’s Footmarks: A Journey Into Our Restless Past; Mike Parker’s Stonehenge: Exploring the Greatest Stone Age Mystery. Also the delightful paper, “The Prehistoric Ritual Landscape of Croagh Patrick, Co. Mayo” (Corlett, 1998)

Select Foundational Sources on the Science of Fasting and Hormetic Stress. See the “Science of Hormetic Stress” above. Also: “Fasting: molecular mechanisms and clinical applications” (Longo & Mattson, 2014); and “A Periodic Diet that Mimics Fasting Promotes Multi-System Regeneration, Enhanced Cognitive Performance, and Healthspan” (Brandhorst et al, 2015).

Select Foundational Sources on the Science of Depression and Body-Based Treatments. For studies showing the effect of exercise on depression, see the British Medical Journal review, “Effect of exercise for depression: systematic review and network meta-analysis of randomised controlled trials” (Noetel et al, 2024); also, the more specific, “Effects of high-intensity interval training on depressive symptoms: A systematic review and meta-analysis” (Tao et al, 2024). Relatedly, this study shows a reduction in depression and rumination from a 90-minute walk in nature: “Nature experience reduces rumination and subgenual prefrontal cortex activation” (Bratman et al., 2015) 

For the papers exploring the role of neuroplasticity (driven by BDNF) in reducing depression, see “Brain-Derived Neurotrophic Factor, Depression, and Physical Activity: Making the Neuroplastic Connection” (Phillips, 2017); and “The Role of BDNF on Neural Plasticity in Depression” (Yang et al, 2020)

For the studies investigating sauna-level heat and cold-water swimming as depression treatments, see Select Foundational Sources on the Science of Sauna and Cold Plunge — Relating to Emotional Health, in Book 2 Notes

Select Foundational Sources on the Science of Depression and SSRIs — For Teenagers and Children. For the science showing that the most commonly prescribed antidepressants (SSRIs) are largely unproven in teenagers, a general audience could look first to Johann Hari’s excellent 2018 book, Lost Connections: Why You’re Depressed and How to Find Hope. He makes this case convincingly on pp. 21-46

For the studies demonstrating this, look to the 2016 paper: “Comparative efficacy and tolerability of antidepressants for major depressive disorder in children and adolescents: a network meta-analysis” (Cipriani et al, 2016). It reviewed 34 trials—which tested 14 antidepressant treatments with 5,260 participants—and was published in The Lancet. It concluded, “these drugs do not seem to offer a clear advantage for children and adolescents.” 

A 2021 analysis largely reinforced this, referencing the impact of newer antidepressants on depression symptoms as “small and unimportant” compared with placebo. “New generation antidepressants for depression in children and adolescents: a network meta-analysis” (Hetrick et al, 2021). There are counterpoints to this. And—due to the widely divergent nature of “depression”—effects vary. 

Select Foundational Sources on the Science of Endorphins and Synchronization. For the paper broadly linking endorphins to physical and mental health, look for “Why friendship and loneliness affect our health” (Dunbar, 2025). For the evidence that endorphins cause humans to biologically bond look for “The brain opioid theory of social attachment: A review of the evidence” (Machin & Dunbar, 2011). 

The original paper documenting how endorphins cause the “Runners High” is “The Runner’s High: Opioidergic Mechanisms in the Human Brain” (Boecke et al, 2008). The breakthrough study from Robin Dunbar’s lab—demonstrating how endorphin levels double as a result of synchronization: “Rowers’ high: behavioural synchrony is correlated with elevated pain thresholds (Cohen, Dunbar, et al, 2010).

Subsequent papers from Dunbar’s lab show similar effects of synchronization: that it doubles endorphin release and causes people to bond. This was found with group music: “Group music performance causes elevated pain thresholds and social bonding in small and large groups of singers” (Weinstein et al, 2016); synchronized dancing: “Synchrony and exertion during dance independently raise pain threshold and encourage social bonding” (Tarr, Dumbar et al, 2015) and 

 “Silent disco: Dancing in synchrony leads to elevated pain thresholds and social closeness” (Tarr, Dunbar et al, 2016); group laughter: “Laughter influences social bonding but not prosocial generosity to friends and strangers” (Dunbar et al, 2021); and watching tear-jerker movies: “Emotional arousal when watching drama increases pain threshold and social bonding” (Dunbar et al, 2016).

A broad paper laying out the evidence that endorphins are released during group music performance —and that these endorphins also cause humans to bond is found in “The origins and function of musical performance” (Dunbar, 2023) 

You also should not miss Robin’s writing on the endorphins released when humans drink alcohol together: Look for “Why Drink Is the Secret to Humanity’s Success: Alcohol has been more valuable to our species’ survival than we might imagine” in the Financial Times (Dunbar, 2018)

Select Foundational Sources on the Science of Nature Immersion. The earliest studies demonstrating how nature immersion boosts our physiological and mental health came out of Japan, where they proved the health benefits of “forest bathing” (“Shinrin-yoku”). Look for the seminal 2010 paper “Physiological Effects of Shinrin-yoku” (Park et al, 2010). This 2018 paper analyzed more than 100 other studies, and corroborated many health benefits (lower blood pressure, lower resting heart rate, lower cortisol): “The health benefits of the great outdoors: A systematic review and meta-analysis of greenspace exposure and health outcomes” (Twohig-Bennett et al, 2018). This 2019 paper zeroed in on 20 minutes as the right exposure length for stress reduction:  “Urban Nature Experiences Reduce Stress in the Context of Daily Life Based on Salivary Biomarkers” (Hunter et al, 2019).

For specific health benefits: This paper showed a 20% improvement in working memory from a 2.8 mile (roughly 1-hour) walk: “The cognitive benefits of interacting with nature” (Berman et al, 2008). An improved immune response (Natural Killer Cells, anti-cancer proteins) was demonstrated by 4 hours of forest-walking in this study: “A day trip to a forest park increases human natural killer activity and the expression of anti-cancer proteins in male subjects”  (Li Q et al, 2010). A reduced fear response was demonstrated by a 1-hour nature walk in this study: “How nature nurtures: Amygdala activity decreases as the result of a one-hour walk in nature” (Sudimac et al, 2022). And improved sleep was demonstrated through a range of nature immersions in this review: “Greenspace exposure and sleep: A systematic review” (Jong Cheol Shin et al,  2020)

For Attention Restoration Theory, a foundational work is Rachel Kaplan and Stephen Kaplan’s The Experience of Nature: A psychological perspective (1989). For the Old Friends Theory, two foundational works are “Old friends for breakfast” (Rook & Brunet, 2005); and “Microbial ‘Old Friends’, immunoregulation and stress resilience” (Rook, Lowry & Raison, 2013)

For the layperson, look to Florence Williams’s beautifully written, The Nature Fix: Why Nature Makes Us Happier, Healthier, and More Creative (2017).

Select Foundational Sources on the Science of Nature Exposure in Hospitals. For the famous 1984 study showing that patients with a view of greenery recover faster from surgery: “View through a window may influence recovery from surgery” (Ulrich, 1984). 

A range of later studies have shown that nature imagery alone (even without a window) improves patient outcomes. For example, look at “The Influence of Exposure to Nature on Inpatient Hospital Stays: A Scoping Review” (Guidolin et al, 2024);  “Benefits of Nature Imagery and Visual Art in Healthcare Contexts: A View from Empirical Aesthetics” (Cardillo et al, 2025); and “Distraction therapy with nature sights and sounds reduces pain during flexible bronchoscopy: a complementary approach to routine analgesia” (Diette et al, 2003). One recent VR-based study indicated that even the color green alone could impact outcomes: “Understanding the Influence of Window Views, Plantscapes, and Green Décor in Virtual Reality Hospital Rooms on Simulated Acute-Care Patients’ Stress Recovery and Relaxation Responses” (Suess et al, 2025)