BDNF, or Brain-Derived Neurotrophic Factor is a protein that acts on specific neurons of the Central Nervous System (CNS, which is the brain and spinal cord) and the Peripheral Nervous System (PNS, which is outside the brain and spinal cord).

BDNF is a neurotrophin, where neurotrophins like BDNF functions to improve the survival of existing neurons, encourage the growth of new neurons, and encourage the differentiation of new neurons and synapses. Differentiation is referring to a stem cell specializing into one particular cell type.

Another example of a neurotrophin is Nerve Growth Factor (NGF), which is found mostly concentrated in the Peripheral Nervous System, with a trace found in the CNS.

In comparison, BDNF is the neurotrophin mostly found concentrated in the brain, with the highest levels located in the hippocampus followed by the cerebral cortex.

Brain-Derived Neurotrophic Factor (BDNF) has multiple important functions in the brain. BDNF protects brain neurons against the stress hormone cortisol, including the Hippocampus. The Hippocampus is an area of the brain that is responsible for controlling mood, memory, and learning. BDNF is like the fertilizer that encourages neurons to connect to one another and grow, making BDNF vital for neuroplasticity & neurogenesis. BDNF turns on genes to produce more neurotransmitters and neurotrophins, reduce self-destructive cellular activity, releases anti-oxidants, and stimulates the production of proteins used as building material for axons and dendrites.

So as you can gather from these facts, BDNF is vital for brain health.

So you may ask, what increases and what decreases the amount of BDNF present in the brain? Well, extremely high levels of cortisol decreases BDNF. However, anti-depressants and exercise do just the opposite.

Intense exercise spikes BDNF significantly, but the spike is short lived and drops off quickly. Sustained, moderate intensity exercise spikes BDNF to a lesser extent, but it stays elevated for a longer period of time, even after you’ve finished exercising, and ultimately results in a greater total increase in BDNF. Moderate pace walking is also effective. Therefor, sprinting, jogging, hiking – all cardiovascular exercise is beneficial, and a combination might be even better for your brain. I imagine that the longer and more frequently you exercise, the better it likely is for your brain (as long as you don’t overtax your body and increase your cortisol too much). Trail running and nature hikes are likely doubly effective, since you get environmental enrichment in the form of the novel stimulation of nature + the BDNF spike resulting from cardiovascular exercise.[1]

Depression suppresses BDNF levels. Suicidal patients have significantly low levels of BDNF. This may indicate that our mood is tied to our BDNF levels.

Note that many people in the United states live a sedentary lifestyle. That means many people in the United States do not exercise enough. Exercise is beneficial by improving mood & memory by increasing the level of BDNF in the hippocampus. So one may conclude that the lack of exercise experienced in our modern lifestyle is a major factor that leads to depression.

Some studies show that BDNF is a necessary ingredient for anti-depressants to work. On the other hand, some studies show that Anti-Depressants may restore a patient’s BDNF levels. So what is going on exactly? I will have to do more research here.


  1. Brain Gain: Aerobic Exercise Pumps Up Gray Matter [reddit]

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