Adults Can Grow New Brain Cells: (Part 7: What hinders the growth of new brain cells)

We discussed how to increase the growth of new cells in our brains to enhance our cognitive abilities and emotional resilience throughout Delve’s blog. However, to make the most out of such opportunities, we need to pay equal attention to what gets in the way of neurogenesis. After all, there is little point in trying to be healthy if we are poisoning ourselves at the same time.

When we look at the decrease of neurogenesis, one of the main names we have to remember are neurotoxins. They come in many forms: emotional stress, inflammation, lack of sensory, mental, and emotionally rich environments. Let’s have a look at the most important ones in depth:


When our bodies get sick or injured, there are many internal mechanisms that battle the wrongdoers. Inflammation is one of them. It clusters white blood cells to the damaged area and often results in redness, swelling, heat and pain. These are normal processes that ensure the infection does not contaminate the area and does not spread further into our bodies. However, due to dietary, environmental and other factors, sometimes the blood cells fail to attack the outsiders or the infection becomes too intense, and the good cells turn against the body itself. This process is called chronic inflammation and is behind or involved in major health problems: cancer, stroke, diabetes, nephritis, Alzheimer’s, heart disease, ALS, Huntington’s disease, Parkinson’s, sclerosis and others.

To add insult to the injury, chronic inflammation can go unnoticed for long periods of time leading to a point of damage beyond repair. But all is not as pessimistic as it seems. There are many activities that may provoke chronic inflammation, as well as there are many things that we can do to avoid it. Eliminating and reducing these elements may prove vital to avoid chronic inflammation:

  • Toxic chemicals (smog, pesticides).
  • Smoking, drinking alcohol.
  • High sugar levels.
  • Free radicals (oxidation).
  • Obesity and excess fat.
  • Physical stress (including not sleeping, colds, gum disease)
  • Emotional stress (anxiety, fear, loneliness, depression, isolation, bad relationships etc.)

Scientists have also discovered a link between chronic inflammation and neurogenesis. As the good cells turn upon our bodies and start inflicting damage, the growth of new brain cells is affected as well. Limiting the aforementioned activities and checking the inflammatory levels during the yearly physical exam are reliable ways to ensure positive neurogenesis.


As we have discussed in our blog post about Emotions, Love and Relationships (Part 4) our brains can be divided into three layers: a reptilian brain, the limbic system, and the neocortex. Interestingly, stress can be categorized into three categories as well. Basic physical stress (lack of food or imminent danger) affects the humans’ reptilian brain. Social stress (e.g. a high school party or a work meeting) affects the advanced limbic system and is found only in primates. Lastly, humans experience psychological stress which affects our neocortex. Psychological stress includes activities like anticipating a public talk, reflecting if it went poorly or forecasting future. In addition to that, it includes stress experienced when our self-images are threatened, which tends to happen to all of us.

Will I be able to meet this work goal? Will this person like me? Can I get over this particular loss? Will I be okay in the future? It is questions we have all asked ourselves and questions that may produce a certain level of stress. Since almost no one has a bullet-proof, solid, and integrated protection against the interpersonal world, such stress can become regular and chronic.

The aforementioned ongoing stress is the root cause of many problems. When faced with it our bodies releases hormones including adrenaline, noradrenaline, cortisol, and other glucocorticoids. Over the short-term these help our bodies cope with the particular situation. However, long-term exposures are harmful and may lead to damage ranging from weakness of immune system, muscle recovery to anxiety, depression, and memory problems. Studies have shown that such chronic stress can shrink our hippocampus, the part essential for neurogenesis (as we have covered in Part 5 of our blog) as well as cognitive, memory and emotional abilities. MRI and CT brain scans revealed that under extreme stress, it is much harder to form new memories and manage our emotions. The connections between neurons is withered and new cell growth is slowed. The worrying part is that hippocampus is in charge of regulating glucocorticoid levels, but as it gets damaged because of stress, it is unable to control the very things that are hurting it.

Worryingly, a recent poll has found that half of millennials are so stressed they cannot sleep at night, and 39% said their stress levels have increased over the past years. Economic uncertainty, work pressure, bad relationships, inauthentic friendships, being constantly online, plugged in to mobile phones, computers, rarely getting downtime – are all sources of stress. All of them are damaging our brains and slowing down neurogenesis. The good news is that everything is within our power to control and change. How we relate to stressful events is key. Bad stress can be transformed into good stress that makes our brain sharp and prepared to deal with uncertainties. Our blog post on Emotions, Love and Relationships (Part 4) goes deeper into how we can deal with bad relationships.


Direct damage to the brain

Our brains are highly complex but also highly vulnerable instruments. A crash to the head, such as a car accident or a fall, can disturb the internal connections of neurons within the brain. A single concussion doubles the chances of a person getting Alzheimer’s or other brain diseases later in life. Even chemicals and environmental pollution can result in damage to the brain. For example, mercury, which accumulates by eating fish, is the second most neurotoxic substance in the world (after plutonium). Even a tiny amount of mercury destroys neurons. Lead is another pollutant that is inhaled through air and may lower our I.Q.’s and reduce brain function. Children are especially susceptible to these chemicals as they can only tolerate lesser amounts of them.

Therefore, limiting our exposure to polluted air, watching our diet, protecting our bodies are all ways to ensure our brains are healthy and neurogenesis stays intact.


What happens when you put a mouse into an environment without any physical or social stimulation (no running wheels, no places to explore, no interaction with other mice, no colours or sounds, no change in the daily life)? The mouse falls into depression, lethargy and complete stop of neurogenesis. Similar results can be expected for humans showing us just how important environmental stimulation is. We can categorize the different types of stimulation into 4 groups:

  • Includes exercise, diet, colour, music, sensory stimulation.
  • Personal contact, genuine care, relationships, attachment etc.
  • Intellectual tasks, reading, having conversations about ideas, learning new things, exposure to novelty.
  • Spiritual meaning, meditation, different practices.

We went into greater deal into each of these into our previous posts. The point is – if there is a deprivation of any of these stimulants, neurogenesis slows down and fewer than half of new brain cells survive to become working parts of our brain. However, when placed in an enriched environment the number increases to 80-100% of new brain cells. By providing novel challenges to the brain, we ensure that the growth of new brain cells never stops.

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