Effects of Cannabis on Brain Health and Function

The impact of cannabis consumption on the human brain and its activity has long been a topic of discussion among medical professionals. Thanks to legalization efforts in the United States and other Western countries, as well as advances in neuroscience research, scientists have begun to study the mechanisms by which individual cannabinoids affect the human brain. However, this research is still largely in its early stages. Nevertheless, scientific literature is increasingly featuring articles on the effects of cannabis on brain function and health, often reaching surprisingly contradictory conclusions.

On one hand, it is well known that cannabis use significantly affects the formation of short-term memory. On the other hand, many studies indicate that regular cannabis use may strengthen long-term memory and, overall, protect the brain from the formation of amyloid plaques and deposits—major factors in the development of Alzheimer’s disease and other neurodegenerative disorders.

Of the more than 200 different compounds in cannabis, about 85 are various cannabinoid compounds. Currently, scientists are primarily focused on studying the cognitive and therapeutic effects of just two: THC and CBD, both present in relatively high concentrations in any cannabis plant. The short- and long-term effects of cannabis on the human brain and its functioning can largely be explained by tracking these compounds and their influence on the body’s endogenous cannabinoid receptors, CB1 and CB2.

The Endocannabinoid System and Its Functions

The human endocannabinoid system is a dense network of nerve endings divided into two groups, each with different functions and activation mechanisms, and present throughout all body tissues. These receptors are closely linked to the central and peripheral nervous systems. Generally, CB receptors are involved in modulating all biological systems in the body, from regulating emotions and memory formation to maintaining homeostasis and physiological functions. In simple terms, the endocannabinoid system acts as a protective network, allowing the body to respond to pathogens, injuries, and nutrient imbalances, helping it return to a state of natural balance and well-being more quickly.

Since its discovery about 60 years ago, the endocannabinoid system has been studied enough for doctors to recognize its importance in protecting and maintaining the viability of the human body, as well as to understand how it interacts with cannabis compounds to produce a range of therapeutic effects.

As previously mentioned, the network of receptors is divided into two groups, each differing in function and sensitivity to certain cannabinoids, whether endogenous or exogenous. CB1 receptors are more common and are mainly located near the endings of the central nervous system in the brain. Because of this, CB1 receptors are found in every part of the brain and in the tissues of all organs. The main activator of this group is the endogenous cannabinoid anandamide, as well as its plant-based structural and functional analog, THC. THC (which is a stronger activator than anandamide) acts on CB1 receptors, explaining its ability to produce feelings of mental stimulation, relaxation, and intoxication.

CB2 receptors, on the other hand, are located at the endings of the peripheral nervous system and in all neural nodes of the immune system. These receptors modulate the body’s immune and inflammatory responses, suppressing pain and discomfort, reducing inflammation in soft tissues, and numbing muscles. Unlike CB1, CB2 primarily interacts with CBD, which does not activate but rather blocks the receptor, producing a healing effect.

While other, lesser-known cannabinoids also interact with both groups of receptors to varying degrees, THC and CBD have the most significant impact. This explains why most research focuses on these compounds and their unique properties.

As noted, THC is the main activator of CB1 in cannabis. In small and moderate concentrations, it can stimulate creativity and imagination, improve focus, and enhance the ability to concentrate on tasks. In excess, however, THC can overstimulate the brain, causing once-clear thoughts to become jumbled, and turning calm and creative flow into nervousness or a strong desire to sleep. In such cases, an unprepared person may experience a prolonged panic attack or paranoia, or feel weakness and nausea, often followed by vomiting.

CBD, in contrast, is known as the “healing cannabinoid” and has a markedly different psychoactive effect, producing pain relief and a calming sensation. Recent studies have shown that this is due to its ability to block CB2, which slows the transmission of neural impulses from the receptor, in turn activating enzymes that break down anandamide and THC in the body. Interestingly, this ability to slow the breakdown of other cannabinoids (and some other psychoactive compounds) allows CBD to modulate and soften the psychoactive properties of THC. In other words, adding CBD to a product with a high THC concentration significantly reduces the risk of negative side effects. In high enough doses and in equal proportion to THC, CBD can even suppress the intoxicating effects of cannabis, allowing medical users to benefit from both cannabinoids without the risk of intoxication.

The Biphasic Effect of Cannabinoids: Why Dosage Matters

While the effects of cannabis are largely determined by each individual’s physiology and method of consumption, the most crucial factor is the concentration of cannabinoids and their ratio in the product. As previously mentioned, THC, like any other cannabinoid, has a biphasic effect depending on its concentration. In small doses, it produces one effect; in large doses, the opposite. This explains the universal effects of intoxication and overdose when consuming pure THC in large amounts, and the sedative, tonic effects when used in small amounts. For this reason, doctors practicing cannabis medicine advise patients to start with low doses and gradually increase as needed.

This effect can also be seen as the “therapeutic window” of cannabis—a dosage range that provides therapeutic benefits without noticeable side effects. Because cannabis flowers have a narrow therapeutic window due to the difficulty of measuring cannabinoid concentrations and the influence of various terpenes and impurities, both doctors and patients often prefer extracts and tinctures of specific cannabinoids, which are easier to dilute to the desired therapeutic dose. This effect is evident in treating any condition responsive to cannabis therapy. For example, in chronic pain management, low concentrations of THC provide a tonic, sedative, and analgesic effect, while high doses increase nervousness, which in turn intensifies the sensation of pain.

It’s also important to remember that cannabis compounds interact with each other. In addition to the effects of impurities and terpenes, cannabinoids themselves modulate each other’s effects depending on dosage and ratio. Taking these factors and individual biochemistry into account is essential for determining the optimal extract dosage or selecting the right strain. Ideally, the compounds should be present in similar concentrations to modulate each other’s effects.

Subjective Effects of Low or Moderate Cannabinoid Concentrations:

• Improved mood, relaxation, and mild euphoria
• Drowsiness (a slightly higher CBD to THC ratio softens this effect)
• Stimulation of imagination and creativity
• Blocking or reducing various types of pain
• Suppression of nausea and vomiting
• Stimulation of appetite

Subjective Effects of High or Very High Cannabinoid Doses (Overdose):

• Strong feelings of paranoia
• Nervousness and aggression
• Disorientation and loss of train of thought
• Increased sensation of pain and nausea
• Mild visual and auditory hallucinations (rare, with extremely high THC doses)

Returning to the fact that scientists currently present conflicting data on cannabis consumption and the effects of cannabinoids on physiological and psychological processes, Dr. Mike Hart, chief consultant for the medical resource Marijuana for Trauma, offers the following explanation:

“Unfortunately, such contradictions in the scientific literature are due to the fact that most studies are conducted by small groups of scientists funded by private sponsors. Relatively few studies on cannabis and its healing or negative properties are conducted in clinical settings, with large sample sizes and strict control over the trials. For this reason, it is likely that the biphasic effects of cannabinoids, determined by the concentration of active compounds, can be explained by either low or, conversely, excessively high dosages. I have personally experienced the trickiness of this effect. Specifically, my team and I conducted a study on the effects of THC on short- and long-term memory in a group of mice. We found that, in addition to dosage, the frequency of use can greatly influence these processes. Initially, we confirmed the presence of short-term memory impairment in the subjects, but by slightly reducing the frequency of administration, we observed the absence of this effect and other side effects like fatigue and nervousness. By making a small adjustment to the timing of administration, we were able to produce tonic and neuroprotective effects in the animals, allowing them to successfully form short-term memories. For this reason, whether using cannabis for recreational or therapeutic purposes, it is best to start with low doses of cannabinoids and spread out their use rather than consuming everything at once.”