Michael Ferguson, a neuroscientist at Harvard Medical School, grew up Mormon and “quite religious.” Although his beliefs have changed over the years, he “couldn’t deny that there was something happening with those [religious] experiences that was and continues to be extraordinarily meaningful to me,” he says. “As a scientist, I can’t help but wonder what it is about these types of experiences that made them feel so rich and so profound.” 

When Brigham and Women’s Hospital first made plans to open the Center for Brain Circuit Therapeutics a few years ago, Ferguson was on board to join as a junior faculty member and announced he wanted to study the neuroscience of religion. But the soon-to-be center director told him that first, he’d need to help develop and validate a new strategy for understanding cognitive networks, called lesion network mapping. The technique pinpoints how different brain regions work together to produce complex behaviors by looking at how lesions caused by injuries or surgeries in one area disrupt function in other areas.  

In some ways, lesion network mapping is a lot like one of the oldest techniques in neuroscience, in which researchers identify the functions of different brain regions based on what behaviors are disrupted when those regions are injured. For decades, researchers have observed that some patients with temporal lobe epilepsy experienced hyper-religiosity—religious beliefs so intense that they can interrupt daily functioning. 

Lesion network mapping takes the technique further. It relies on the connectome, a wiring diagram of neural connectivity throughout the brain, to help researchers better understand how disruption in one region may affect an entire circuit of connections. “One of the things that’s really novel about lesion network mapping is that we’re not only looking at the focused spot that was removed or that was damaged, but we’re looking at the entire circuit that that spot is attached to,” says Ferguson. It’s a bit like loosening a bulb on a string of Christmas lights and seeing that not only that light, but many other lights, go out. 

Having validated the technique with a study using it to investigate memory in 2019, he was able to apply it to the questions that inspired him as soon as the Center for Brain Circuit Therapeutics opened in 2020. In June, Ferguson and his team published a study in Biological Psychiatry showing that brain lesions that connect to the periaqueductal gray (PAG), an area deep in the brain involved in processes such as pain modulation, fear conditioning, and altruism, seem to be associated with religiosity and spirituality.   

“The discovery that religiosity and spirituality may be related to a distinct circuit in the brain is fascinating,” Uffe Schjoedt, who studies the neuroscience of religion at Aarhus University, writes in an email to The Scientist. “Lesions studies represent a unique possibility for neuroscientists to examine how physical changes to the brain impact thought and behavior.” 

Sparse evidence

Studies on religion and the brain, a field dubbed neurotheology or neurospirituality, are sparse. The research is “difficult to get funded, and also difficult to get published in high-level journals because it’s not considered legitimate,” says Myrna Weissman, an epidemiologist and psychiatrist at Columbia University. 

There’s also a misconception that scientists are trying to disprove religious beliefs. Ferguson emphasizes that none of these studies will confirm or refute the validity of specific religious beliefs. Instead, the research is “helping us to understand how religion and spirituality interact with brain systems,” he says.  

The nascent field so far is characterized by disparate findings that are rarely replicated and difficult to reconcile into a cohesive hypothesis. Last year, one group used MRI to measure anatomical differences among individuals at three different regions of the brain—including areas in the temporal lobe implicated in hyper-religiosity after epilepsy surgeries—that they thought might process religious experiences. After questioning 211 individuals about their religiosity and spirituality and scanning their brains, the researchers found no differences in gray matter volume between those who said they were religious and those who said they weren’t. That team did not specifically look at the periaqueductal gray.  

The study didn’t show that religiosity isn’t reflected somewhere in the brain, just that it isn’t associated with these specific anatomic changes, argues Ferguson, adding that it underscored the need for more complex approaches that can identify disruptions in functioning that might not be associated with an anatomical difference. 

Other inconsistencies also plague the literature. Researchers define “spirituality” and “religiosity” differently in each study, for example. “Most of these studies have been based on a single measure,” says Connie Svob, a neuropsychiatrist in Weissman’s lab. Some might ask participants how important religion is to them, while others ask how often they pray or if they consider themselves religious people. “What does it mean to consider yourself a religious person?” she asks. This lack of precision is one reason that Schjoet says he “remains skeptical” of Ferguson’s findings, which relied on a single yes or no question to determine a person’s spirituality in one part of the study. 

Functional strategies

Despite the slow start to making headway into pinpointing the neuroanatomical correlates of religion, interest in the field is “changing drastically,” adds Weissman, as researchers find new ways to probe the brain.  

Rather than studying where religious beliefs seem to live in the brain, many teams are seeking to understand religion’s role in complex behaviors such as reward processing and the risk of developing depressive disorders.  

“Our brain can change according to different things that we do,” notes Svob. “So why would that not extend to religious practices?”  

In 1982, Weissman started a study on risk factors for depression with a cohort of 220 patients who had been diagnosed with major depressive disorder. The researchers gave these patients and matched controls who did not have depression regular surveys about behaviors that might be protective against developing depression or experiencing relapse. Over the next several decades, the researchers recruited the cohort’s children, grandchildren, and even great-grandchildren into the study. One of the behaviors that correlated with lower risk of developing or relapsing into depression was placing a high importance on religion. “If you are at high risk for depression, believing in the importance of religion was protective for yourself, but it’s also protective for your children,” says Svob.  

If you are at high risk for depression, believing in the importance of religion was protective for yourself, but it’s also protective for your children.

—Connie Svob, Columbia University

In the 2010s, the team decided to look for differences in the brain between patients at high risk for depression who said religion was important and those who didn’t. Using MRI, the team scanned the brains of 106 children and grandchildren of people from the initial cohort.  

One of the major findings, says Svob, was that participants who believed in the importance of religion had less cortical thinning—a reduction in the volume of neuronal tissue in specific areas of the brain that’s considered a hallmark of depression risk—than did those who said they didn’t. While the study couldn’t show causality, Svob says, it suggested “that religious beliefs might have some kind of neuroprotective effect, and there might be a biomarker in the brain that might actually be related to religion, spirituality, and depression.” Since then, the team has gone on to use EEG and MRI to explore the relationship between religion and other behaviors and depression.  

In Ferguson’s study, he and his colleagues recruited 88 patients who were scheduled to undergo neurosurgery to remove brain tumors. Both before and after the surgeries, the participants filled out surveys that asked about religiosity and spirituality. After their surgeries, 30 patients said their religiosity and spirituality decreased, while 29 said it increased, and another 29 didn’t experience any change. 

The researchers compared their answers to the sections of the brain the patients had had removed and found that patients whose spirituality changed in either direction had a portion of the brain removed that connected to the PAG. 

“The finding that the network they identified is centered on the PAG is a bit surprising, as that region is not usually flagged in neuroimaging studies on spirituality,” says Patrick McNamara, a neuroscientist who studies religion at Boston University School of Medicine. But he adds that based on the functions of neurons found there, it makes sense that the region would be involved in spirituality. 

The future of neurotheology

One of the outstanding questions is whether changes in the brain cause changes in religiosity or if religiosity changes the brain. Svob says that “more research, especially prospective in nature, is needed to determine potential causality and neuroprotection. From what we’ve observed, it is certainly possible [that religiosity and spirituality cause neuroprotective changes in the brain], but nowhere near certain.” On the other hand, Ferguson’s lesion network mapping study suggests that changes in the brain can cause changes in religiosity and spirituality. He points out that some previous work has pointed to a genetic basis for spirituality, but also emphasizes that this is the “Wild West frontier of science,” and there’s no current consensus among researchers about causality. 

One of the limitations of many of the studies, including Ferguson’s, is that they tend to include mostly Christian patients rather than purposely recruiting patients of various belief systems. Researchers who spoke with The Scientist say they hope that in the future, they’ll be able to include more diverse groups of participants and investigate whether there are any differences in how various religions might interact with the brain. 

Studying religion might help integrate it better with medicine, Ferguson says, speculating that it could one day play a role similar to that of meditation. “[When] mindfulness meditation was first being introduced into the cultural West, people thought that it was really eccentric, and they were really suspicious about it. Whereas now, that’s a very standard complement for [treating] anxiety or for depression, or for any number of clinical symptoms.” 

Correction (July 14): The original version of this story stated that researchers have observed that epilepsy patients often experience hyper-religiosity associated with surgery to remove portions of the temporal lobe. In fact, observations of hyper-religiosity in people with temporal lobe epilepsy are not related to surgery. The Scientist regrets the error.