For most of the twentieth century, the scientific consensus was that the adult brain was essentially fixed. You were born with a certain number of neurons, and once they died, they were gone forever. The brain was thought to be a static organ — powerful, yes, but fundamentally unchangeable in its architecture after early childhood. Adult neurogenesis research reveals the brain is more adaptable than once thought.
That belief has been overturned. Research over the past several decades has shown that the adult brain is far more plastic than previously imagined — and, in certain regions, it can actually produce brand new neurons throughout adulthood. This process is called adult neurogenesis, and it has changed the way neuroscientists think about learning, memory, depression, aging, and the brain’s capacity for self-repair.
In adult mammals, neurogenesis has been most reliably documented in two regions of the brain. The first is the hippocampus — specifically the dentate gyrus, a subregion involved in forming new memories and distinguishing between similar experiences. The second is the subventricular zone, which lines the brain’s fluid-filled ventricles and in some species generates neurons that migrate to the olfactory bulb, the brain region involved in smell. Adult neurogenesis is most active in the hippocampus, critical for memory formation.
The hippocampus is particularly interesting because of its central role in memory, learning, and emotional regulation. The fact that this region keeps generating new neurons in adulthood suggests that neurogenesis may be connected to the brain’s ability to update itself with new information and adapt to new circumstances. Boosting adult neurogenesis may improve mood, memory, and cognitive resilience.
The Controversy About Human Neurogenesis
The question of whether human adults experience meaningful neurogenesis has been surprisingly contentious. Early studies, including a landmark 1998 paper by Eriksson and colleagues, provided some of the first direct evidence that new neurons are born in the adult human hippocampus. This was exciting news that attracted significant attention and shaped two decades of research.
However, a 2018 study published in Nature cast doubt on these findings. Using postmortem brain tissue and improved methods for detecting immature neurons, researchers reported finding very few newly born neurons in adult human brains compared to what earlier studies had suggested. This sparked a scientific debate that is still ongoing.
More recent work using single-cell RNA sequencing has offered a partial reconciliation. These studies have identified neural stem cells and immature neurons in the adult human hippocampus, suggesting that some level of neurogenesis does persist — though possibly at lower rates than in rodents, and possibly declining significantly with age. The scientific picture is still being refined, but the possibility of adult human neurogenesis remains very much alive.
What Promotes Neurogenesis?
One of the most practically significant findings in neurogenesis research is that this process can be enhanced or suppressed by lifestyle factors. The same behaviors that generally support brain health appear to promote the production of new neurons in the hippocampus — and the behaviors that damage brain health appear to inhibit it.
Physical exercise is the most robustly supported neurogenesis enhancer. Aerobic exercise in particular — running, swimming, cycling — has been shown in numerous animal studies to dramatically increase the rate of new neuron production in the hippocampal dentate gyrus. The effect is believed to be mediated partly through increased levels of brain-derived neurotrophic factor, or BDNF, a protein that supports the growth and survival of neurons.
Environmental enrichment also plays a role. Animals raised in stimulating, varied environments with opportunities for exploration, social interaction, and novel experiences show higher rates of hippocampal neurogenesis than animals in barren, unchanging conditions. This has led researchers to hypothesize that mentally stimulating activities may support neurogenesis in humans as well, though direct evidence is harder to gather.
Sleep is another important factor. The brain does much of its consolidation and repair work during sleep, and studies suggest that neurogenesis is higher in animals that get adequate sleep. Chronic sleep deprivation, on the other hand, appears to suppress new neuron production — one of the many reasons poor sleep has such far-reaching effects on cognitive and emotional health.
What Suppresses Neurogenesis?
Chronic stress is one of the most potent inhibitors of neurogenesis. When the brain is under sustained stress, elevated cortisol levels actively suppress the production of new neurons in the hippocampus. This may be part of why chronic stress and depression are associated with a measurable reduction in hippocampal volume over time — the ongoing stress doesn’t just damage existing neurons but prevents the hippocampus from replenishing them.
Alcohol, particularly heavy and chronic use, also suppresses neurogenesis. Studies in rodents have shown significant decreases in hippocampal new neuron production with heavy alcohol exposure, and there is evidence that this damage can partially reverse during periods of abstinence — which may partly explain some of the cognitive improvements people experience when they stop drinking.
Aging naturally reduces neurogenesis as well. The rate of new neuron production in the hippocampus declines steadily with age, which may contribute to the memory changes associated with getting older. Whether interventions like exercise can meaningfully offset age-related decline in neurogenesis is an active area of research.
Neurogenesis, Depression, and Mental Health
The connection between hippocampal neurogenesis and depression has been one of the most intriguing threads in this field. People with major depression often show reduced hippocampal volume, and many antidepressant medications — particularly SSRIs — have been shown to promote neurogenesis in the hippocampus of rodents. Some researchers have proposed that this increase in neurogenesis may actually be the mechanism through which antidepressants work, rather than (or in addition to) their direct effects on neurotransmitter levels.
This “neurogenesis hypothesis of depression” is still being tested, and the relationship is likely more complex than a simple cause-and-effect. But it does suggest that supporting neurogenesis through exercise, adequate sleep, stress management, and mental stimulation may have genuine protective effects for mood — not just through vague “brain health” benefits, but through specific biological mechanisms.
There’s also evidence that new neurons in the hippocampus play a role in emotional processing, particularly in the ability to distinguish between safe and threatening situations. Deficits in this function — possibly related to impaired neurogenesis — may contribute to anxiety disorders and PTSD, where individuals struggle to recognize that previously dangerous situations are now safe.
Neurogenesis and Memory
The hippocampus is essential for forming new declarative memories — the kind you can consciously recall, like facts, events, and experiences. New neurons in the dentate gyrus appear to contribute to a specific memory function called pattern separation: the ability to distinguish between similar memories and avoid confusing them.
This is more important than it might initially sound. If your hippocampus can’t distinguish between a parking lot you visited yesterday and one you visited last week, you’ll constantly confuse similar memories. Robust pattern separation relies on a steady supply of new neurons that can form new, distinct representations rather than lumping new experiences together with old ones.
As neurogenesis declines with age, pattern separation becomes less efficient — which may account for some of the “can’t quite remember where I put that” experiences that become more common in middle and older age. Whether interventions that boost neurogenesis can meaningfully slow this decline is something researchers are actively investigating.
Practical Implications
You can’t directly observe your own neurogenesis, and there are no supplements that have been proven to reliably boost it in humans. But the research does support a fairly clear set of lifestyle recommendations for anyone who wants to support their brain’s capacity for renewal and adaptation.
Regular aerobic exercise remains the most evidence-backed intervention. Even moderate amounts — thirty to forty-five minutes of brisk walking or jogging most days of the week — appear to have meaningful effects on hippocampal health. Prioritizing sleep, managing chronic stress, limiting alcohol, and keeping the mind engaged with learning and novel experiences all contribute to the broader picture.
The brain you have today is not the brain you have to keep forever. Neurogenesis is one of the clearest biological demonstrations of the brain’s ongoing capacity for change — a process that rewards the habits we often know we should have but find it easy to delay. Understanding the science behind it is one more reason to stop delaying.
See Nature Neuroscience’s research on adult neurogenesis for the full scientific review.
Frequently Asked Questions
Can the adult brain really grow new neurons?
Yes, adult neurogenesis occurs primarily in the hippocampus. Research confirms that exercise, learning, and healthy lifestyle factors promote new neuron growth and brain plasticity throughout adulthood.
What stimulates neurogenesis in adults?
Key stimulants of adult neurogenesis include aerobic exercise, learning new skills, adequate sleep, caloric restriction, stress reduction, and environmental enrichment.
Does chronic stress prevent brain cell growth?
Yes, chronic stress and elevated cortisol levels are among the most significant inhibitors of neurogenesis. Managing stress through mindfulness, exercise, and social support is critical for brain health.
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