Cannabis and the Brain: From Adolescence to Adulthood

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What are the effects of cannabis on brain development in adolescents and adults? This article discusses the consequences for mental health, cognition, and increased psychosis risk.

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Introduction to Cannabis’ Influence on Brain Maturation

In recent decades, cannabis consumption among teenagers and young adults has climbed sharply, troubling doctors, educators and parents regarding potential ramifications for psychological wellbeing and cognitive growth. Alongside rising potency in today’s cannabis, burgeoning use, encouraged by legalization and the existence of so-called “medical” marijuana, is especially disquieting. Today, it’s common to find cannabis strains boasting 29% THC, while some concentrated forms like oils and waxes contain astonishing 76% THC concentrations, thirty times what was available a couple of decades back. Adolescence through the early twenties is a critical period in brain development, characterized by widespread changes in neural growth and connectivity. Introducing potent cannabis compounds during this phase causes profound effect. It is worrisome that some of the changes might be very long lasting as this is also a time when widespread pruning of neuronal connections occurs, “freezing,” as it were, certain pathological patterns of response to the outside world. At Sterling Institute, we are committed to advancing comprehension of these issues and cultivating strategies to assist mental health of youth navigating challenges related to cannabis use. For more data on how we can help, visit

Understanding Cannabis Components and Mechanisms

The effects of cannabis on the brain arise from how cannabis interacts with the natural endocannabinoid system (ECS) in the human body. The ECS plays a pivotal role in governing diverse physiological processes, including mood, appetite, pain sensation, and memory formation. Cannabis, particularly its psychoactive molecule tetrahydrocannabinol (THC), binds to cannabinoid receptors in the brain, altering the normal operation of the ECS. This alteration has serious consequences especially during adolescence, a crucial period for neurological maturation. Exposure to cannabis in these formative years has been linked to impaired cognition, serious psychiatric disorders, and compromised coordination between the mind and the body in for example driving capacity. These discoveries underscore the importance of a thorough and realistic understanding of cannabis’s impact on the developing adolescent brain to guide prevention and intervention strategies. The popular notion that cannabis is harmless is a dire mistake.

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Moreover, the escalating potency of cannabis products presents additional hazards. Recent analyses show a significant rise in the THC content of cannabis, with some strains containing up to 29% THC, and concentrated products achieving levels as lofty as 76% THC. This boost in potency, coupled with a decline in the perceived risk of cannabis use among youth, highlights an urgent necessity for targeted public health education and preventive initiatives. It is essential to communicate the even more serious risks associated with high-THC cannabis products, particularly to adolescents and their families. 

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Impact of Cannabis on Adolescent Brain Development

The developing brain is particularly vulnerable to the adverse effects of cannabis, showing substantial degradation (even visible on MRI) in both gray (neuronal) and white (connections) matter. These changes are not superficial. As an example, reductions in gray matter structures, crucial for handling information, and compromises in white matter integrity, essential for communication between brain areas, have been seen in the brains of adolescent cannabis users. This architectural reconfiguration of the developing brain contributes to deficits in cognition, memory, attention, and decision-making.

Additionally, functional imaging research (fMRI) shows how these anatomical changes translate to areas of reduced brain activity that match observed performance deficits. Teenagers who use cannabis show altered and reduced brain activation when engaging in intellectual tasks compared to their non-using peers. A 2019 New York Times article summarizes these findings:

Numerous studies show that marijuana can have a deleterious impact on cognitive development in adolescents, impairing executive functionprocessing speedmemoryattention span and concentration. The damage is measurable with an I.Q. test. Researchers who tracked subjects from childhood through age 38found a consequential I.Q. decline over the 25-year period among adolescents who consistently used marijuana every week. In addition, studies have shown that substantial adolescent exposure to marijuana may be a predictor of opioid use disorders.

There is a critical need for strategies to mitigate these effects especially in the face of overwhelming popular claims that cannabis is harmless. Early intervention is critical. Experience teaches that heavy users of cannabis require at a minimum Intensive Outpatient Programs, with whom Sterling professionals are happy to collaborate, to break through cannabis addictions.

Effects of Cannabis on Adult Brain Function

The effect of cannabis on the adult brain differs by age and sex. As brain physiological maturation continues until on average twenty-six, adults experience consequences similar to adolescents that attenuates with age. The presence of cannabis use disorder (CUD) amplifies these adverse effects in proportion to its severity. For reasons not well-understood, studies have shown that these risk factors are stronger in young women during young adulthood, This sex-specific vulnerability highlights the importance of interventions that are sensitive to the unique needs and risks faced by women in this age group.

Due to its developmental sensitivity, the adolescent brain is properly the main focus of concern. However, the enduring effects of cannabis on adults warrant attention as well. Adolescent cannabis users suffer from the consequences of physical degradation of the brain and consequent losses of cognition and IQ. They suffer as well from significant increases in the incidence, and worsening of existing psychiatric disorders such as psychosis, schizophrenia and bipolar disorder. In adults past the stages of brain maturation, deficits in cognition are less prominent, and so it is the impact on mental health that persists and stands out. Perhaps the single most prevalent concern in adults is the worsening of anxiety disorders among adults who use cannabis on a regular basis. The most serious concern, however, is the worsening of bipolar disorder.

Cannabis-Induced Psychosis and Depression and Bipolar Disorder Risks

The link connecting teen cannabis consumption and an increased vulnerability to psychosis and bipolar disorder is intricate and strong, but not yet fully elucidated, influenced by inherited neurobiological features and surrounding environmental and psychosocial influences. A 2023 Danish study of 6,651,765 individuals in Demark, age 16 and into all ages of adulthood, found that cannabis use disorder was associated with an increased risk of both psychotic and nonpsychotic unipolar depression and bipolar disorder. This is presumably because of genetics as well as outside influences.

The brain endocannabinoid system regulates our moods and perceptions. Alterations in this system brought about by cannabis use offer a potential explanation for cannabis’s link to psychotic and bipolar disorders. The presence of cannabinoids from cannabis can disrupt the delicate balance among inhibitory and excitatory circuits employing different neurotransmitters, potentially leading to the characteristic symptoms of various disorders. With greater understanding, it might be possible to intervene early, mitigating the risk of schizophrenia and bipolar disorder.

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Treatment and Prevention 

The current treatments for cannabis use disorder, particularly among young people, heavily emphasize behavioral therapies. These include cognitive-behavioral therapy (CBT), motivational enhancement therapy (MET), Dialectical Behavioral Therapy (DBT), Relapse Prevention Therapy (RPT) and family-based interventions, all of which have shown promise in treating substance use disorders. These are most effective either in combination with or as part of levels of care higher than standard outpatient one-on-one psychotherapy or psychopharmacology. This means highly-structured, group based Intensive Outpatient Programs (IOP, 3 hours daily, 3-5 days a week), Partial Hospital Programs (PHP, 5-7 hours daily, five days a week) or full-time residential programs (1 month minimum stay). 

Prevention strategies are essential in curbing the onset of cannabis use. Psychoeducation, which entails informing individuals about cannabis’s impacts on the brain and mental health, can be a powerful deterrent. By equipping adolescents, parents, and educators with accurate information, we can foster a more informed decision-making process regarding cannabis usage. The Sterling Institute emphasizes the importance of such proactive measures and will partner with structured program services. Those seeking support, guidance, and treatment options can visit the Sterling Institute’s website at for more details.

Standards for the Sale of Medical Marijuana versus Medical Prescription Drugs

A major influence in the spread of cannabis use and of its consequences is the message being sent both by its legalization and by the creation of a “Medical Marijuana” enclave, seemingly a subset of professional medicine, and legally somewhat allied to it, but in practical reality not.

One can get a sense of this reality by comparing what goes into making a cannabis product legal for sale as “medical marijuana” to what goes into the approval of prescription medications. This information is useful as well for considerations of safety.

As of April 2023, regulations for marijuana to be deemed “medical,” and legally saleable by dispensaries, vary somewhat from state to state. Here is a general overview in a number of key states. Cannabis laws are subject to change, so it’s important to consult the latest state-specific regulations for the most accurate information.


  • Licensing: Dispensaries and producers must be licensed by the Connecticut Department of Consumer Protection.
  • Testing: All medical marijuana products must be tested in state-licensed laboratories for potency and contaminants.
  • Packaging and Labeling: Products must be properly labeled with THC content, a list of ingredients, and a warning label. Packaging must be child-resistant and not appealing to children.

New York

  • Licensing: Dispensaries must obtain a license from the New York State Department of Health.
  • Testing: Products are required to be tested for contaminants and potency.
  • Packaging and Labeling: Detailed labeling is required, including dosage, a list of active and inactive ingredients, and health warnings. Packaging should be tamper-evident and child-resistant.


  • Licensing: Dispensing organizations must be approved by the Florida Department of Health.
  • Testing: Mandatory testing for contaminants and THC/CBD levels is required.
  • Packaging and Labeling: Packaging must be child-resistant, and products must include labeling with specific information about the product, including THC and CBD content.


  • Licensing: Businesses must be licensed by the Colorado Marijuana Enforcement Division.
  • Testing: Testing for potency, contaminants, and residual solvents is required.
  • Packaging and Labeling: Labels must include potency information, a list of ingredients, and a universal THC symbol. Packaging must be child-resistant.


  • Licensing: Facilities must be licensed by the Michigan Marijuana Regulatory Agency.
  • Testing: Products must be tested for potency and contaminants.
  • Packaging and Labeling: Packaging must be child-resistant and tamper-evident. Labels must include potency, weight, and a health warning statement.


  • Licensing: Dispensaries must be registered with the Cannabis Control Commission.
  • Testing: Mandatory testing for pesticides, heavy metals, potency, and more.
  • Packaging and Labeling: Products must be labeled with potency, a list of ingredients, and health warnings. Packaging must be child-resistant and not appealing to children.


  • Licensing: Dispensaries must be licensed by the Arizona Department of Health Services.
  • Testing: Testing for contaminants, potency, and purity is required.
  • Packaging and Labeling: Products must include labeling with health warnings, potency, and a list of nonorganic pesticides, herbicides, and fungicides used in cultivation.

These general requirements give an overview, but some specifics vary as to what forms of cannabis are allowed (e.g., flower, edibles, concentrates), as well as detailed packaging, labeling, and testing standards.

The cost for obtaining compliance approval for medical marijuana products is minimal and is recouped immediately upon sale. 

“Using our best estimates of average batch size (8 pounds) and failure rate (4%) in the 2019 California market, we estimate testing cost at $136 per pound of dried cannabis flower, or about 10 percent of the reported average wholesale price of legal cannabis in the state.” The time from planting to dispensary is under one year.

Prescription Medications

Prescription medications must be FDA approved for the treatment of a particular condition (indication) although they may also be used for other conditions. The process for a proposed medication to receive FDA approval and an indication for use involves a challenging, immensely costly, and systematic series of steps designed to ensure the drug’s safety, efficacy, and quality. 

One study assessed both capitalized and out-of-pocket costs [for a single medication] as about US$1.8 billion and $870 million, respectively.” (Wikipedia)

“In an analysis of the drug development costs for 98 companies over a decade, the average cost per drug developed and approved by a single-drug company was $350 million.” (Wikipedia)

The time from concept to pharmacy for a prescription medication is 15 to 20 years. The time to recoup costs is an additional 5 years while under patent.

Here is an overview of the requirements and stages involved in just the FDA approval process, regulated nationally, at the Federal level:

Preclinical Research

  1. Laboratory and Animal Testing: Before testing a new drug in humans, the drug sponsor (usually a pharmaceutical company) must conduct extensive preclinical research. This involves laboratory tests and studies in animals to evaluate the drug’s safety profile, including its toxicity, pharmacokinetics (how the drug is absorbed, distributed, metabolized, and excreted), and pharmacodynamics (the drug’s effects on the body).
  2. Investigational New Drug (IND) Application: If preclinical data suggest the drug is potentially safe and effective, the sponsor submits an IND application to the FDA. The IND includes results from the preclinical studies, the drug’s manufacturing information, and the proposed clinical trial protocols. The FDA reviews the IND to ensure that participants in the trials will not be subjected to unreasonable risks.

Clinical Trials (Human Testing)

Clinical trials are conducted in phases, each designed to answer specific research questions:

  1. Phase 1: These trials are the first stage of testing in human subjects and primarily focus on assessing the drug’s safety, determining a safe dosage range, and identifying side effects. Phase 1 trials usually involve a small number of healthy volunteers (20-100).
  2. Phase 2: In this phase, the drug is given to a larger group of people (100-300) to evaluate its efficacy, further assess its safety, and determine the optimal dose for efficacy with minimal side effects. Participants in this phase usually have the condition that the drug is intended to treat.
  3. Phase 3: These trials are conducted on larger populations (300-3,000 or more participants) and aim to confirm the drug’s effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow the drug to be used safely. Phase 3 trials are pivotal for the drug’s approval process.

FDA Review and Approval

  1. New Drug Application (NDA): If the clinical trials demonstrate that the drug is safe and effective for its intended use, the sponsor submits an NDA to the FDA. The NDA includes all data from the preclinical and clinical trials, information on how the drug behaves in the body, manufacturing specifications, proposed labeling, and suggestions for physician prescribing.
  2. FDA Review: The FDA reviews the NDA, assessing the drug’s safety and efficacy data, the proposed labeling, and the manufacturing processes. This review process involves a detailed examination of the data and may include consultations with advisory committees of external experts.
  3. Approval: If the FDA determines that the drug’s benefits outweigh its risks for the intended use, it approves the drug for sale in the U.S. market. The approval comes with specific indications for use, dosing recommendations, and requirements for post-marketing surveillance to monitor adverse effects and ensure the drug’s safety profile remains acceptable.

Post-Marketing Surveillance (Phase 4)

After approval, the drug enters the market, but the FDA continues to monitor its safety and effectiveness. Manufacturers are required to submit periodic safety updates and may conduct post-marketing studies to gather additional information about the drug’s long-term effects, its effectiveness in the general population, and any rare side effects that may not have been identified in clinical trials.

This FDA approval process is designed to ensure that all marketed medications meet the necessary standards for safety, efficacy, and quality, protecting public health while providing access to new therapeutic options.


The pathway to market for medical marijuana is regulated at the state level, and in general requires only that minimal contamination is present, and its cannabis content and potency measured and stated.  No trials in animals or humans are required to test for claimed efficacy nor even safety. The entire pathway for a large batch of product takes under a year at most and costs about $10,000 recouped immediately at sale.

By contrast the pathway to market for prescription medical drugs involves a standardized, rigorous process of clinical trials and FDA approval focused on ensuring safety and efficacy. The entire pathway takes 15-20 years and costs $1.6 billion dollars per medication recouped five years after approval.

Thus the term “medical” applied to both requires careful assessment as to what each use means and as to whether “medical” marijuana is “medical” in the same sense as with prescription drugs.

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