Substance Use Disorder

Waqar Husain et al. (2026) · Brain and behavior

This systematic review of 105 studies examined how religious and spiritual practices -- meditation, prayer, chanting, ritual, and mystical experience -- show up in brain scans. It pooled evidence across eight traditions (Buddhism, Christianity, Islam, Hinduism, Santo Daime, Spiritism, Sant Mat, and mixed traditions) and seven brain-imaging methods, filling a gap left by earlier reviews that each covered only one practice or one faith. Neurotheology, the scientific study of how spiritual experience relates to brain function, asks whether these ancient practices leave a measurable, functional signature on the nervous system. Researchers searched three major databases from their earliest records through mid-2026 and found 450 candidate studies; after removing duplicates and screening for eligibility, 105 studies remained. Each had to study real human participants using an objective brain-measurement tool -- functional or structural MRI, EEG, MEG, PET, SPECT, or similar -- during an actual religious, spiritual, or contemplative practice, not passive exposure to religious words or images. Because the studies varied enormously in tradition, practice, and method, the team combined findings narratively rather than statistically averaging them. Meditation studies (the largest group, 35 studies) consistently found quieter activity in the brain's default mode network, the circuit active during mind-wandering and self-focused thought, alongside more efficient attention-related brain activity in long-term practitioners. Prayer (21 studies) activated brain regions used for understanding other people's minds when prayer was personal and improvised, suggesting the brain treats sincere prayer like a real conversation, and activated reward circuitry during peak spiritual feelings among some worshippers. Chanting and recitation (25 studies) calmed emotional brain circuits -- OM chanting, for example, reduced activity along the same pathway targeted by an approved medical nerve-stimulation therapy. Mental-health-relevant findings (14 studies) included a randomized trial in which loving-kindness meditation eased depression symptoms in diagnosed patients, and a mindfulness program that lowered stress-hormone levels months later. Eleven studies of unusual states -- near-death imagery, ayahuasca ceremonies, and trance -- showed the most widespread brain-network changes of any practice type. The review's authors state plainly that religious and spiritual practices are neurologically real, measurable behaviors, not just subjective reports, and that the brain circuits they engage overlap with those disrupted in depression, anxiety, and addiction. They stop short of claiming these practices treat any diagnosed condition, since most studies involved healthy volunteers rather than patients. The search covered only English-language, peer-reviewed studies, and the wide variety of traditions and methods meant the team could describe patterns but not calculate a single combined effect size.

Nicole Redvers et al. (2020) · PloS one

This scoping review examined 249 published articles to map what is known about traditional Indigenous medicine as practiced across North America — the healing systems, ceremonies, and practitioners used by the region's approximately 7.5 million Indigenous peoples. Traditional Indigenous medicine treats a person as a whole being of body, mind, and spirit connected to family, community, and land, with healing understood as restoring "connectedness" through practices that may or may not involve a physical medicine in the Western sense. The review was built with an Indigenous Elder as co-author and content expert, deliberately using an Indigenous-led approach to synthesis rather than a purely Western critical-review method. Researchers searched six academic databases and multiple grey-literature sources from the earliest records through June 2020, screening thousands of records down to 249 included articles spanning 1888 to 2020. Ethnobotany and plant-physiology papers were excluded to keep the focus on practices and practitioners. The team sorted the literature into five themes — general traditional medicine, integration with Western medicine, ceremonial healing practices, usage patterns, and healer perspectives — without performing a formal quality assessment, a choice the authors describe as consistent with Indigenous research protocols rather than a gap. Three findings stand out. First, traditional-healer consultation rates varied widely by community, from about 17% to over 70% of people surveyed, and multiple studies found most patients never told their physician about this use. Second, within the 30 articles on ceremonial healing, a study of incarcerated adults given jail-based sweat lodge ceremonies for alcohol use disorder reported a 7% re-incarceration rate versus an estimated 30-40% for non-participants (interpret with caution: one program, not a controlled trial). Third, a 13-week "Indigenous Healing and Seeking Safety" program combining traditional and trauma-focused approaches cut trauma symptom scores by 55% (p=0.001) in a small pilot of 17 participants. The review's honest limitation is its own scope: it catalogues what has been published, it does not grade or verify the quality of any individual study, and much of the older literature was written by non-Indigenous observers whose framing the authors flag as sometimes outdated or inappropriate. For seekers and clinicians alike, the practical takeaway is that traditional Indigenous medicine is widely used, often undisclosed to conventional providers, and under-served by rigorous evaluation — a call for more research and better clinician-healer collaboration rather than a verdict on what works.