Opinion: We think a baby’s gut microbiome could be key to lifelong brain health

Picture a baby sleeping in a crib. Every second, her brain is forming more than a million new neural connections. The scaffolding for language, memory, attention, and thought is going up in real time, wire by wire. We don’t yet know who she will become; yet much of her future self depends on what reaches her now, in the earliest months of her life. We accept that the brain is shaped by developmental plasticity, developing and adapting in response to experience and environment. Yet medicine tends to frame conditions affecting the brain across the lifespan, from autism and ADHD to Alzheimer’s disease, as primarily genetic or social in origin. Until we understand the biological mechanisms that translate experience and environment from birth into lasting changes in brain development and function, we are operating with only part of the picture. The cost of that missing piece may be trillions of dollars and millions of lives each year. The question is: What are the biological systems involved in brain developmental plasticity? Researchers have identified the window between conception and a baby’s second birthday as a critical period of brain development. Genetics, nutrition, parent-child interaction, and sleep all matter, but growing evidence suggests the developing brain also takes its instructions from somewhere perhaps unexpected: the gut microbiome. The gut microbiome is more than a passenger in early life. It may be one of the biological systems through which brain developmental plasticity operates. When that system is functioning well, the brain receives signals it has evolved to expect during critical windows of early development. But what if those signals never arrive, or arrive at the wrong time? And what if environmental factors we know shape neurodevelopmental outcomes partially do so by disrupting those signals? Research is linking early gut microbiome disruption to differences in socialization, learning, and memory. Disruption describes a microbiome that develops off course: It can be short on the beneficial bacteria and key functions that a developing brain expects, weighted toward harmful ones, or maturing too slowly or quickly. Variables that are common practice in modern medical and food systems, like cesarean birth, antibiotic usage, formula feeding, and maternal BMI, can contribute to this disruption. Scientists are investigating whether these accumulating pressures on the developing gut microbiome may contribute to rising neurodevelopmental differences, like autism with high support needs. This is the premise of FORM, a $50 million Wellcome Leap program designed to rigorously investigate links between the early life gut microbiome and neurodevelopmental challenges, including autism with high support needs. The aim is to conduct this much needed research in parallel with the development of new product opportunities that could improve developmental resilience and reduce neurodevelopmental and co-occurring difficulties before they emerge, by promoting a well-functioning maternal and early infant microbiome. The consequences of early gut microbiome disruptions may not stop at childhood. Researchers at Washington University found markedly different gut microbiomes in people at the earliest preclinical stages of Alzheimer’s, differences correlated with amyloid and tau accumulation before any cognitive symptoms appeared. Scientists at New York University and Rutgers have proposed that this trajectory may begin in infancy, with early antibiotic exposure being one factor that can initiate a cascade that contributes to Alzheimer’s decades later. Both lines of work are early, unanswered questions remain, and neither establishes causation yet. But together they suggest the early-life gut microbiome may be less a chapter in child development than a strand that runs through an entire life. To be clear about the science: On autism, debate continues and causation is not established. On dementia, the research is only now emerging. We need more rigorous, large-scale research into the gut-brain axis across the life course, conducted in partnership with communities with lived experience to ensure research is socially trustworthy. And we need the infrastructure to act on what we already know. Right now, we are not even close. By investing in capabilities that can measure and potentially modify key gut microbiome functions in early life, we can ask not just how to react to differences and disease once they appear, but whether supporting developmental resilience from conception through to age 2 can set children up for lifelong brain health. During this period, the mother’s body and the infant’s body are one system. We treat them as two. This division makes administrative sense. It makes almost no biological sense. We know that immune, inflammatory, metabolic, and stress signals influence brain development in a child before and after birth. We also know that factors ranging from infection and antibiotics to nutrition, socioeconomic position, and chronic stress can shape neurodevelopmental outcomes in a child across this same period. Many of these same factors also shape the maternal and developing infant gut microbiome. So, what if they converge on a common biological pathway? Sitting at the crossroads of immunity, inflammation, and metabolism, the maternal and infant gut microbiomes may help translate environmental influences into the biological signals that shape brain development across pregnancy and infancy, one connected window of developmental plasticity. This is not an argument against antibiotics, caesarean births, formula, or any other feature of modern life. Nor is it a story about medicine harming children. It is a story about how the science of brain development is outpacing the clinical systems built to act on it. The conditions that shape the microbiome are rarely individual choices made in isolation. They are societal forces that may influence one of the earliest biological systems involved in an infant’s brain development. Yet our clinical systems still treat maternal health and infant health as separate worlds. Connecting maternal and infant care — shared records, joint protocols, and gut health on the prenatal and postnatal agenda — is the most immediate structural change we can make. One reason the early childhood brain development window closes without intervention is that our diagnostic tools were not built to look through the mother-child nexus. Neurodevelopmental screening in the United States typically begins between 9 and 30 months. Providers rarely diagnose autism or neurodevelopmental delay before ages 3 to 6, and the behavioral assessments they rely on detect difficulties when they have already occurred. We are too late in addressing the underlying biology and miss the key windows of developmental plasticity. What we need are objective biological biomarkers that catch gut microbiome and brain vulnerabilities months or decades before differences manifest — and years or decades before dementia. Getting there requires not just better instruments. It requires a shift in how providers and parents understand brain conditions: not as purely behavioral, detectable only once a toddler shows difficulties, but as biological vulnerabilities that take shape much earlier in life. Tools to identify a disrupted maternal and infant gut microbiome are already being developed, but screening without a protocol for what to do next is incomplete medicine. We need to fund the full pipeline: validating the diagnostics, building clinical capacity to deploy them, and ensuring that children with disrupted gut microbiomes have real options to restore resilience before early disruption translates into potentially different neurodevelopmental outcomes or later cognitive disease. Worldwide, $1.7 trillion is spent annually on brain disorders. Nearly all of it goes to people already in crisis, past the point where the underlying biology could have been redirected, whether in infancy or in adolescence or midlife. Early investment won’t erase those costs, but it would reduce the cost later in life — including the projected global cost of dementia, which is rising toward $2.8 trillion by 2030. Making that case rigorously is itself part of the work. Without serious health-economics research on early intervention, microbiome-based tools will stall on the way to clinical adoption because no one has yet shown what they save in terms a reimbursement system understands. The Davos Alzheimer’s Collaborative works to close that gap, making the case that brain diseases including Alzheimer’s must be met with prevention and detection across the life course, now starting as early as maternal health and the infant gut microbiome. Now let’s focus back on that baby in the crib. She is being shaped right now by organisms she will never know exist, through a process medicine has only begun to map. The gut-brain conversation sounds abstract until you consider what it may mean in practice: The architecture and resilience of her neural scaffolding, built in her first years, may influence whether she can still recognize a face across a room at 80. Holly Baines, Ph.D., serves as program director for Wellcome Leap’s FORM, a $50 million program researching the role of the maternal and developing infant gut microbiome in neurodevelopment. George Vradenburg is a veteran corporate leader turned global health advocate, driving Alzheimer’s research, prevention, and policy change through UsAgainstAlzheimer’s, the Davos Alzheimer’s Collaborative, CEOi, and Business Collaborative for Brain Health.