Exercise improves your health and promotes your lifespan, but did you know that exercise can also improve your memory? Fascinatingly, recent research indicates that exercise-induced improvements in memory are mediated by the endocannabinoid system (ECS).
In this article, we will discuss how exercise affects memory, how exercise affects the ECS, and how exercise improves memory through the ECS.
But before we dive in - did you know that exercise is one of the 15 Factors that can impact your cannabis experience? According to the aggregated data of anonymized Jointly users, exercise at any point in your cannabis experience makes it better. But exercising before you use cannabis has the greatest impact.
Exercise has been shown to enhance memory function in lab studies, but how does exercise exert this effect?
The question is challenging because exercise affects your brain at multiple levels: molecular, cellular, and structural. However, researchers have identified various mechanisms at each level by which exercise could improve memory.
For example, at the molecular level, exercise increases brain derived neurotrophic factor (BDNF)—a key molecule involved in brain plasticity, learning, and memory.
These molecular changes “may induce cellular changes, including…neurogenesis, synaptogenesis, and angiogenesis,” which are the formation of new neurons, new synapses between neurons, and new blood vessels, respectively.
And these cellular changes alter the structure of the brain, increasing “white matter, grey matter, receptor activity, neural activity, and cerebral blood flow.” Over time, consistent (chronic) exercise leads to improved memory function. But even a single bout of exercise (acute) can positively impact your memory.
However, the ECS also plays an important (and little-known) role in exercise-induced memory improvement.
In humans, the ECS is made up of the type 1 cannabinoid receptor (CB1) and the type 2 cannabinoid receptor (CB2), the endogenous ligands (AEA and 2-AG) that are also known as endocannabinoids (eCBs), and the enzymes that produce and degrade the ligands.
Ligands are signaling molecules that bind to receptors on cells. When a ligand binds to a receptor on a cell, it produces an effect in the cell. Usually receptors only accept one (or a few) specific ligands.
CB1 receptors are found on neurons throughout the brain and the peripheral nervous system. THC is a CB1 receptor agonist, meaning THC binds to CB1 receptors and produces a signal.
The ECS can be thought of as “a lipid-signaling system…that modulates neurotransmitter release.” When eCBs (or exogenous cannabinoids) bind to CB receptors on neurons, the release of that neurotransmitter is suppressed. For example, if eCBs bind to receptors on a GABAergic neuron, the release of GABA will be suppressed.
Researchers have known there is a connection between cannabinoids and memory for decades, ever since early studies observed that cannabis intoxication impairs short term memory function.
As we discussed in Does Weed Cause Memory Loss?:
Most psychoactive effects from cannabis are caused by THC binding to CB1 receptors in the brain. THC creates its effects by binding to receptors in “brain regions that are vital for memory formation, including the hippocampus, amygdala, and cerebral cortex.”
THC is a CB1 receptor agonist, meaning THC binds to the CB1 receptor and produces a signal. In animal studies, CB1 agonists impair short term memory in a dose dependent manner. Higher doses lead to greater short-term memory impairment.
Conversely, administration of CB1 antagonists enhances “memory consolidation.” An antagonist blocks agonists from binding to a receptor and producing a signal. Researchers found that blocking CB1 receptors increases the release of acetylcholine—a neurotransmitter involved in memory and learning.
While it may seem like there is a simple relationship between CB1 receptors and memory, where increased CB1 signaling impairs memory, the reality is more complicated. For example, chronic, low dose THC has been shown to reverse age-related cognitive decline in animal studies. (Want to know more? Check out: Can Cannabis Improve Brain Health in Seniors?)
These paradoxical findings are related to the fact that cannabinoids have biphasic effects, where a low dose of cannabinoids has a stimulating effect, while a higher dose has an inhibitory effect.
So, how does this relate to exercise and memory?
The psychological benefits of exercise are so powerful that scientists suggest that exercise “may be considered as a psychoactive drug.” Remarkably, many of the psychological benefits of exercise are related to the ECS. For example, the famous “runner’s high” has been found to be caused by eCBs rather than endorphins.
Animal studies have shown that without CB1 receptors on GABAergic neurons, exercise does not relieve anxiety. Other studies indicate that the rewarding effects of exercise are related to the CB1 receptor.
If you aren’t familiar with the fascinating ways that your ECS links your body and mind, you might want to check out Your Unique Endocannabinoid System. We discuss the ancient evolutionary roots of the ECS, how a healthy ECS can improve your psychological wellbeing, and how exercise, meditation, massage, cold, and stress alter your ECS—for better or for worse.
But for now, all you need to know is that exercise impacts your ECS in various beneficial ways. For example, exercise increases levels of AEA (the bliss molecule) and makes your CB1 receptors more sensitive.
Different types of exercise, or exercising in different conditions, may produce different effects on the ECS. For example, strenuous hiking at high altitude significantly increases serum AEA from baseline, more so than strenuous hiking at normal altitude.
Emerging research indicates that the ECS plays a complex role in how exercise influences memory.
For example, exercise-induced neurogenesis in the hippocampus (part of your brain related to memory) is dependent on CB1 receptors.
Related to this finding, researchers found that treadmill running improves spatial memory in mice, but that improvements in spatial memory could be prevented by administering a CB1 receptor antagonist. As we discussed above, the amygdala and hippocampus both play an important role in memory. Now that we understand how exercise impacts the hippocampus through the ECS, let’s look at the amygdala.
The ECS is critically involved in our stress response and mood, partly because CB1 receptors are expressed in high density in the amygdala. The amygdala is part of your brain related to fear-related memories and emotional processing.
In general, people tend to remember emotionally arousing experiences better than dull experiences. At a neurobiological level, emotionally arousing experiences (like stress or exercise) increase levels of stress hormones like cortisol and epinephrine, which bind to receptors in the amygdala “to induce endocannabinoid (eCB) synthesis.”
Once the eCBs are synthesized and released, they bind to GABA receptors in the amygdala and inhibit GABA release. This process alters the balance of excitatory and inhibitory inputs in your brain, and ultimately enhances your memory of the emotionally arousing event.
More research is needed to tease out the precise relationship between the ECS, exercise, and memory. But it’s safe to say that moderate physical activity will improve your wellbeing and help you enjoy the cannabis experience you're after.
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