Scary Ways Marijuana Impacts the Developing Brain

These days, people talk about marijuana, pot, weed, or cannabis as a natural health remedy for issues like chronic pain, nausea, and anxiety. But this controversial substance, which is revered by some for its calming effects, comes with a host of side effects, especially in adolescents and teens.

Mounting research shows that cannabis use leads to significant impacts on the developing brain. And they aren’t good.

In this blog, you’ll discover the scary ways cannabis use alters human brain function. And how these changes can have lifelong consequences.

WHAT IS CANNABIS?

With so much information about cannabis coming at you from news sources, social media, and health professionals, it can be challenging to know fact from fiction. However, a wealth of emerging science is helping clear up the cannabis confusion.

To simplify things, understand that cannabis is comprised of over 120 components called cannabinoids. Two of the most well-researched cannabinoids are cannabidiol (CBD) and tetrahydrocannabinol (THC).

• CBD: A psychoactive cannabinoid, CBD is not intoxicating and does not produce a feeling of euphoria. Basically, it won’t make you feel “high.” It’s commonly used to help decrease inflammation and reduce pain, but it may also be used to alleviate anxiety, nausea, migraines, and seizures. CBD is widely available in the form of oils, gummies, and other products for these purposes.
• THC: This is the primary psychoactive compound found in cannabis. It is responsible for producing the “high” commonly associated with its use. 

CANNABIS EFFECTS ON NEURODEVELOPMENT AND VULNERABILITY

1. Endocannabinoid System (ECS) Disruption

The endocannabinoid system plays a crucial role in brain development, including synaptic pruning, neurogenesis, and the regulation of neurotransmitter release. This system includes cannabinoid receptors (CB1 and CB2), endogenous cannabinoids (endocannabinoids like anandamide and 2-AG), and enzymes for their synthesis and degradation.

• CB1 Receptors: These are abundant in brain regions involved in cognitive function, emotion, and reward, such as the prefrontal cortex, hippocampus, amygdala, and basal ganglia.
• CB2 Receptors: Although less abundant in the brain, they are present in microglia and are involved in immune response and neuroinflammation.

THC, the psychoactive component of marijuana, binds to CB1 receptors, leading to altered endocannabinoid signaling. During adolescence, the ECS is especially active and critical for proper brain maturation. Research suggests that disruption by exogenous cannabinoids can interfere with these processes.

2. Synaptic Pruning and Neuroplasticity

 In the developing brain, several important processes occur during adolescence. Using marijuana may interfere with this critical phase.

• Synaptic Pruning: During adolescence, the brain undergoes extensive synaptic pruning, eliminating weaker synapses and strengthening others. This process is vital for efficient neural circuitry and cognitive function. A 2021 study shows that THC exposure can disrupt synaptic pruning, leading to aberrant neural connections and impaired cognitive abilities.
• Neuroplasticity: Marijuana affects neuroplasticity, the brain’s ability to reorganize and form new neural connections. Research shows that THC can impair long-term potentiation (LTP), a process crucial for learning and memory.

3. Neurogenesis

The hippocampus, a region critical for learning and memory, continues to generate new neurons throughout life. Chronic THC exposure can reduce hippocampal neurogenesis, leading to memory deficits and cognitive decline, according to a study in Translational Psychiatry. 

CANNABIS IMPACTS ON NEUROTRANSMITTER SYSTEMS

Neurotransmitters are the chemical messengers used by the nervous system to allow neurons to communicate with each other or other part of the body. Because these neurochemicals transmit information between the brain and body, they are critically important to overall health and well-being. Specific neurotransmitter systems that are affected by marijuana use include the dopaminergic, glutaminergic, and GABAergic systems. 

4. Dopaminergic System

• Reward Pathway: Evidence suggests that THC affects the dopaminergic system by increasing dopamine release in the mesolimbic pathway (reward pathway). Chronic use can lead to dysregulation of dopamine signaling, contributing to altered reward processing, increased risk of addiction, and mood disorders.
• Cognitive Functions: Dopamine is also crucial for executive functions, including attention, working memory, and decision-making. Disruption in dopamine signaling can impair these cognitive functions.

5. Glutamatergic and GABAergic Systems

• Glutamate: THC reduces glutamate release, affecting synaptic plasticity and cognitive function, according to research. Glutamate is essential for long-term potentiation and memory formation.
• GABA: THC enhances GABAergic activity, which can lead to inhibitory effects on neuronal activity. This imbalance between excitatory and inhibitory neurotransmission can impair cognitive processing and emotional regulation.

STRUCTURAL AND FUNCTIONAL BRAIN CHANGES 

6. Prefrontal Cortex

The prefrontal cortex (PFC), responsible for executive functions such as decision-making, planning, and impulse control, is one of the last brain regions to mature. THC exposure during adolescence can alter the development of the PFC, leading to long-term deficits in these functions.

• Structural Changes: Imaging studies show that adolescent marijuana users may have reduced gray matter volume in the PFC.
• Functional Impairments: Functional MRI (fMRI) studies indicate altered PFC activity during tasks requiring executive function and decision-making.

7. Hippocampus

The hippocampus is particularly vulnerable to THC due to its high density of CB1 receptors.

• Structural Changes: Chronic marijuana use is associated with reduced hippocampal volume.
• Memory and Learning: Functional deficits in the hippocampus manifest as impairments in spatial memory and learning.

LONG-TERM BEHAVIORAL AND COGNITIVE CONSEQUENCES

8. Cognitive Decline

• IQ and Academic Performance: Longitudinal studies suggest that early marijuana use is associated with a decline in IQ and poorer academic outcomes. These cognitive impairments can persist even after cessation of use.
• Attention and Memory: Deficits in attention, working memory, and verbal memory are commonly observed in adolescent marijuana users. 

9. Mental Health Issues

• Psychosis and Schizophrenia: Marijuana use can increase the risk of developing psychotic disorders, such as schizophrenia. The risk is higher with early onset and frequent use.
• Mood Disorders: Marijuana use is associated with an increased risk of psychiatric disorders, such as clinical depression and anxiety disorders. Chronic use can exacerbate these conditions and contribute to emotional dysregulation.

10. Addiction and Substance Use Disorders

• Marijuana Use Disorder: Adolescents are more susceptible to developing marijuana use disorder compared to adults. The earlier the onset of use, the higher the risk of developing dependence.

As you can see from this blog, the science on cannabis use during adolescence strongly indicates that it interferes with healthy brain development and leads to lasting consequences. If your teenager is using marijuana regularly, it’s important to seek help from a mental health professional or a specialist in addiction treatment.

The earlier adolescents get help and stop using cannabis, the better for their brain. And with a better brain, they will have a better life.

Dr. Rishi Sood is Associate Medical Director of Amen Clinics Inc. and a child and adult psychiatrist.

Reviewed by Amen Clinics Inc. Clinicians