From the age of three, the 12th Century nun, mystic, poet and composer Hildegard von Bingen had dazzling visions of shimmering points of light and falling stars, which she recorded in detail in her writings and in paintings. The visions were accompanied by revelations about scripture and humanity’s place in the cosmos that she attributed to the will of God.
Neurologist Oliver Sacks famously argued in his 1970 book Migraine that Von Bingen’s visions were “indisputably” migraine auras, echoing an earlier hypothesis by British historian of science Charles Singer, who recognized clinical descriptions of visual disturbance in her art. It is impossible to know whether their shared hypothesis was correct. But it has become evident in recent decades, through the emergence of a science sometimes referred to as neurotheology, that the agonies and ecstasies of religious experience are often reflected in the workings and architecture of our brains.
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Recently, an international team of scientists from Europe, Asia, and the Middle East set out to systematically review how different religious practices show up in the brain. Across the millennia, humans have devised many ways to commune with the divine: meditation, chanting, recitation, musical worship, prayer, mediumistic trance. Some of these practices require more devotional attention than others, and some of them can produce altered states of consciousness. The team synthesized the findings of 105 studies spanning 28 years (1998-2026), across eight different religious traditions, and seven different types of imaging.
Their primary finding was that religious and spiritual practices can produce consistent, and in some cases, lasting changes to how the physical brain looks and works, such as altered gray matter or connectivity between regions. Each practice differed in significant ways from the next, but two regions showed up most frequently in the results. The first was the prefrontal cortex, the brain’s control center, which handles high-level thinking, decision-making, and emotional control. The second was the anterior cingulate cortex, deep in the middle of the brain, which acts as a bridge between the brain’s thinking areas and emotional areas. They published their results in the journal Brain and Behavior.
Devotional OM chanting, for example, seems to calm both the brain’s emotional alarm center, the amygdala, and other emotion centers found deep in the limbic system, the team found. But Buddhist chanting activated the amygdala instead, and seemed to tune the dial on other emotional centers in the limbic system. Likewise, how prayer shaped the brain seemed to depend very much on the type of prayer practiced. Improvised personal prayer was found to activate regions of the brain central to interpersonal connection. Another kind of prayer associated with Sahaja yoga, aimed at quieting the mind, forgiveness, and humility, seemed to deactivate certain parts of the brain associated with external awareness and top-down mental control. And people regularly practicing a type of daily Islamic prayer called Salat, which includes posture, recitation, breathing, and focus, showed differences in the corpus callosum, which connects the two cerebral hemispheres of the brain.
Mediumistic trance, meanwhile, as measured by electroencephalogram, looked like a distinct and healthy form of consciousness and produced specific patterns in slower brain waves associated with a person entering a deeply absorbed, automatic state like flow. Some results were counter-intuitive. Hindu Vedic priests trained from a young age in memorization and recitation of thousands of Sanskrit stanzas showed significantly greater cortical thickness than matched controls, localized to regions of the brain involved in self-discipline and emotional regulation, as well as pitch, rhythm, and melody. But they did not show changes in the hippocampus, the brain’s hub for forming new memories.
While most of the study participants were healthy, a small subset of them suffered from mental health conditions such as depression. The authors suggest that the findings from these studies yield insights helpful in closing the gap in global mental health treatment. Religious and spiritual practices have not yet been reliably shown to treat diagnosed mental health conditions, but they are, they note, “already ubiquitous, freely available, culturally legitimate, and actively engaged in by a substantial proportion of the population.” Many of the studies were also small, correlational, or single case studies, so the findings are preliminary—a starting point.
Hildegard von Bingen never had a brain scan, but nuns who came after her have, and their brains, like those of monks, Vedic priests, and other religious practitioners, show differences that seem to track how they spent their lives. If the causal reading holds, it suggests that humans may have been actively shaping the way their brains work through religious practice since the beginning of time. 
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