Marijuana Use: Detrimental to Youth

American College of Pediatricians – October 2025

ABSTRACT: Marijuana and cannabis have been used medicinally and recreationally for 4000 years and public perception of their use has varied over time.  Currently, the public considers marijuana to pose minimal risk or even beneficial effects, leading to broad legalization throughout the world.  The scientific literature indicates these perceptions are incorrect and that use of cannabis and marijuana have pronounced effects on mental and physical health, particularly for heavy users.  These effects are more pronounced with early use in adolescents.  Adverse effects of marijuana use include reduced school, driving safety and work performance, increased risk of mental illness and schizophrenia, harm to an unborn child if used during pregnancy, and  its role as  a gateway to other drugs of abuse.  We conclude that there is an important role for pediatricians to counsel families regarding these risks and work with the press and legislators to counter the misperceptions regarding marijuana.   

INTRODUCTION

Definition: Marijuana is a strain of the plant genus, Cannabis, that has high concentrations of the psychoactive compound Δ-9-tetrahydocannabinol (THC).¹ THC and cannabidiol (CBD) are plant-derived cannabinoids that interact with receptors in wide variety of human tissues  normally regulated by human cannabinoids, including the immune system and both peripheral and central nervous systems. ²  Since cannabinoid receptors are widely spread  throughout the body, THC and CBD have numerous physical and psychological effects.¹  The highest density of cannabinoid receptors are found in parts of the brain that influence pleasure, memory, thinking, concentration, sensory and time perception, and coordinated movement. Marijuana overactivates the endocannabinoid system, causing the high and other effects that users experience. These effects include distorted perceptions, psychotic symptoms, difficulty with thinking and problem solving, disrupted learning and memory, and impaired reaction time, attention span, judgment, balance and coordination.³

Marijuana Perceptions, Legalization and Use:  Various species of cannabis have been used medically and recreationally for at least 4000 years.¹   In the United States perceptions regarding marijuana use have varied throughout history.  In the modern era, California legalized medical marijuana in 1996 and Colorado did so in 2001. Colorado went a step further in December of 2013 with the legalization of recreational use. Since then, most states have followed.  At the time of this writing twenty-four states allow full use of recreational marijuana by adults, 22 states have either decriminalized marijuana and/or allow medical marijuana and it remains completely illegal in only 4 states.  These numbers are changing as state legislatures pass less restrictive laws or voter initiatives are brought to the ballot.  Against this backdrop of state legalization, we have the incongruity that marijuana is still illegal under federal law.

The broad legalization of marijuana has happened because of the perception that its use is relatively harmless. However, the legalization has also enhanced this perception.  A systematic review by Chiu et al⁴ found that support for legalization for non-medical use of cannabis increased from 12% in the 1970s to 60% in 2016.   Interestingly this increase occurred even in individuals who had never used cannabis.  A great risk of cannabis use was perceived by 40% of the US population in 1998 and only 20% in 2018.  Oh et al⁵ examined data from the National Survey on Drug Use and Health between 2005 and 2014 and found decreasing risk perception for marijuana use during pregnancy in both married and unmarried mothers. In contrast to this Lemos et al⁶ found that the percentage of youth in the United States who felt marijuana was of “no risk” to mental health declined from 14.0 to 11.3% between 2017 and 2021.  Interestingly, the decline was greater in states with legalized marijuana versus those without.  A similar decline was seen in Canada where marijuana use is generally legal whereas a decline was not seen in England which has tightly regulated medical marijuana use.  However, in 2021 the overall percentage of youth who perceived marijuana as “no risk” to mental health was lower in England (4.5%) than in the United States. Much of the perception regarding the benefits of marijuana and its relative lack of harm is driven by social media.  Khademi et al⁷ performed an extensive review of social media perceptions of cannabis use and found that though adverse effects of marijuana use were mentioned, the overwhelming perception was positive and beneficial.

The perception of marijuana or cannabis use as low risk is important since it predicts marijuana use.  Using data from National Survey on Drug Use and Health Survey, Levy et al⁸ found strong correlations between the perception of low risk and ready availability with any past year cannabis use, frequent past year cannabis use, and past year cannabis use disorder both in results from 2002-2014 and from 2015-2018 with higher rates of perceived low risk and availability in the latter years and thus higher overall use.  The increasing perception of marijuana being of low risk was present in all age groups; 12-17, 18-25,26-34, 25-49, and 50+.

Interestingly, despite this increasing perception of marijuana being low risk  following legalization, data from the National Institute of Drug Abuse shows minimal changes in adolescent use over the last 20 years.⁹  Over this period between 10-15% of 8^th graders, 25-30% of 10th graders, 35-40% of 12^th graders report marijuana use in the last year.¹⁰  All these levels decreased during the COVID pandemic.  Trends prior to that show a marked decrease in use during the “War on Drugs” of the late 1970’s and “Say No to Drugs” campaigns of the 1980’s with a rebound during the 1990’s. ^11,12

It is of concern that levels of both smoking marijuana and of vaping marijuana have been increasing in the past 5 years among older adolescents and young adults (ages 19-30).  Marijuana usage is lowest for 18 year olds and increases with increasing age, with most of the increase in usage in the past 5-10 years  coming after age 20.  Daily usage tends to increase with age and is reasonably steady in the 18-20-year-old group over time.¹¹

One additional confounder regarding the legalization of marijuana is the 2018 congressional legalization of hemp for manufacturing which has opened the unintended consequence of a variety of “intoxicating hemp products’ being released and marketed to children and teenagers without warning regarding the nature of the product. States have attempted to close these loopholes, but these attempts have been challenged in court.¹³

Marijuana as a Medicine

Throughout the legalization process, science and regulation of cannabis have operated in “distinct silos” with little communication between the two.² Medical marijuana is considerably different from all other prescription medications in that “[e]vidence supporting its efficacy varies substantially and in general falls short of the standards required for approval of other drugs by the US Food and Drug Administration (FDA).”¹³  The FDA requires carefully conducted studies consisting of hundreds to thousands of patients to accurately assess the benefits and risks of a potential medication. “Prescription drugs are produced according to exacting standards to ensure uniformity and purity of active constituents. Because regulatory standards of the production process vary by state, the composition, purity, and concentration of the active constituents of marijuana are also likely to vary. This is especially problematic because unlike most other prescription medications that are single active compounds, marijuana contains more than 100 cannabinoids, terpenoids, and flavonoids that produce individual, interactive, and entourage effects.”¹⁴

Coehlo et al published a 2023 comprehensive review of the use of cannabis and cannabinoids in health.¹⁵ They reported on the potential use of marijuana and or its related compounds in neurological disorders including multiple sclerosis, epilepsy, Alzheimer’s, Parkinson’s and Huntington’s disease, acute and chronic pain, psychiatric disorders, cancer, and as an antiemetic.  They found that “in clinical trials, the limited available results do not clearly demonstrate a therapeutic advantage in the use of cannabinoids for several pathologies.” A trial in Tourette syndrome showed improvement in tic symptoms after 1 week.  In contrast multiple potential adverse respiratory, cardiovascular, immune, reproductive, psychiatric, and cognitive side effects were reported.

Mental Health Effects 

Marijuana and Addiction: Marijuana is addictive. Between 9 and 30 percent of marijuana users may develop some degree of marijuana use disorder.¹⁶ For adolescents who begin before age 18 there is a 4 – 7 fold increased risk of developing marijuana use disorder.¹⁷  Individuals who use marijuana for physical or mental health reasons are more likely to develop problematic cannabis use.¹⁸

Marijuana and withdrawal symptoms: Long-term marijuana users trying to quit report various withdrawal symptoms including irritability, sleeplessness, decreased appetite, anxiety, and drug craving, all of which can make it difficult to remain abstinent. These withdrawal symptoms can begin within the first 24 hours following cessation, peak at two to three days, and subside within one to two weeks following drug cessation. Younger age is associated with more symptoms.¹⁹ Behavioral interventions, including cognitive-behavioral therapy, motivational incentives (i.e., providing vouchers for goods or services to patients who remain abstinent) and family therapy have proven to be effective in treating marijuana addiction in adolescents.²⁰

 

Marijuana as a Gateway Drug: An additional danger associated with marijuana use observed in adolescents is a sequential pattern of involvement in other legal and illegal drugs. Marijuana is frequently a steppingstone that bridges the gap between cigarette and alcohol use and the use of other more powerful and dangerous substances like cocaine and heroin. A meta-analysis of six studies by Wilson et al²¹ demonstrated 2.76 times greater likelihood of initiating opioid use given prior cannabis use compared to non-cannabis users. Additional analysis of three of these studies found a 2.52 times greater likelihood of transitioning to an opioid use disorder given prior cannabis use compared to non-cannabis users.

Marijuana and the Brain: As mentioned the highest density of cannabinoid receptors is in the brain.¹ It is therefore not surprising that marijuana has pronounced effects on the brain.  These concerns are particularly important during sensitive periods of brain maturation in adolescence during which marijuana use has shown to have significant adverse effects on neuronal plasticity and neuroconnectivity in a variety of animal studies.²² These findings have been confirmed in humans, both adults and adolescents, as  functional MRI and magnetic resonance spectroscopy have demonstrated prefrontal cortex dysfunction, specifically in relation to working memory.²³  Altered neuroconnectivity associated with both acute and chronic exposure to marijuana or THC has also been documented.^24-26 This impairment in neuroconnectivity associated with adolescent cannabis use persists into adulthood.²⁷

In chronic adolescent users, marijuana has a pronounced adverse impact on learning and memory that persists long after the acute effects of the drug wear off. A major study published in 2012 in Proceedings of the National Academy of Sciences²⁸ provides objective evidence that marijuana is harmful to the adolescent brain. As part of this large-scale study of health and development, researchers in New Zealand administered IQ tests to over 1,000 individuals at age 13 (born in 1972 and 1973) and assessed their patterns of cannabis use at several points as they aged. Participants were again IQ tested at age 38, and their two scores were compared as a function of their marijuana use. The results were striking: Participants who used cannabis heavily in their teens and continued through adulthood showed a significant drop in IQ between the ages of 13 and 38—an average of eight points for those who met criteria for cannabis dependence. Those who started using marijuana regularly or heavily after age 18 showed minor declines. By comparison, those who never used marijuana showed no declines in IQ.  Similar findings were found in a US longitudinal study that followed 3385 patients who were between 18 and 30 years of age in 1985 for over 25 years.²⁹ Cognitive function was assessed at the end of the study and included tests of verbal memory, processing speed, and executive functioning. 84.3% of the population reported past marijuana use, but only 11.6% continued using marijuana during middle age. For each five years of past marijuana use, verbal memory decreased significantly even when adjusted for current use. A more recent study found “lower brain activation during a working memory task” in heavy cannabis users.³⁰

These findings of a significant mental decline among those who used marijuana heavily before age 18, even after they quit taking the drug, is consistent with the theory that drug use during adolescence—when the brain is still rewiring, pruning, and organizing itself—has long-lasting negative effects on the brain.

Marijuana and Daily Life: Consistent with marijuana’s impact upon the brain, research demonstrates marijuana has the potential to cause difficulties in daily life and/or worsen a person’s existing problems. Heavy marijuana users generally report lower life satisfaction, reduced mental and physical health, more relationship problems, and less academic and career success compared to their peers who come from similar backgrounds.³¹ Earlier age marijuana use is associated with poorer school performance.³²  Prior day use is associated with lower school and work engagement.³³

A 2014 study³⁴ combined the data of 3 investigations from Australia and New Zealand which compared a series of outcome measures of young adults according to their marijuana use at age 17. The researchers found a significant dose-response effect on all adult outcomes studied. After adjusting for co-variables, compared to those who never used cannabis prior to age 17 (OR 1.0), the odds of graduating from high school by age 25 dropped to 0.78 (95% CI,0.67-0.90) for those who used cannabis less than monthly to 0.61 (95% CI,0.45-0.81) for those using it monthly or more to 0.47 (95% CI,0.30-0.73) for those using it weekly or more to 0.37 (95% CI,0.20-0.66) for daily users. The decrease in attaining a university degree was almost identical. The odds of dependence on cannabis between the ages of 17 and 25 rose progressively from 2.06 (95% CI,1.75-2.42) for less than monthly users to 17.95 (95% CI,9.44-34.12) for daily users, and the odds of other illicit drug use between the ages of 23-25 rose from 1.67 (95% CI,1.45-1.92) for less than monthly users to 7.80 (95% CI,4.46-13.63) for those who were daily users prior to age 17. The odds of making a suicide attempt between the ages of 17 and 25 were increased from 1.62 (95% CI,1.19-2.19) for less than monthly users to 6.83 (95% CI,2.04-22.9) for daily users. While unadjusted odds ratios were increasingly higher for progressively higher amounts of cannabis used before age 17 for both depression (between ages 17-25) and for welfare dependence (at ages 27-30 depending on the study), these differences were no longer significant after adjusting for co-variables. Although the greatest harm was among heavier users, it is most concerning that even less than monthly usage prior to age 17 was associated with a significantly lower educational achievement, and significantly higher rates of drug dependence and suicide attempts.

A 2023 review by O’Neill et al³⁵ reported a variety of adverse events from medical cannabis that impact workplace health safety and performance. The most common  concerns were sedation, nausea/vomiting, and dizziness.  They specifically mentioned decreased alertness and reaction times and concerns regarding operating machinery and driving.  A 2012 systemic review and meta analysis found that odds of motor vehicle collision were nearly doubled with use of cannabis.³⁶

Mental Illness: The link between cannabis use and mental illness was first reported in the late 1800’s in India.³⁷  In fact the findings of the Indian Hemp Drugs Commission 1893-1894 “on ganja [the stronger form of cannabis used India at the time] and lunacy are reasonably consistent with contemporary epidemiological evidence on cannabis and psychosis.” A 1972 paper reported on 46 cases of psychosis associated with excess cannabis use.³⁸  However, there were many uncertainties regarding the direction of this relationship.

During the 1980s, Dr. Sven Andreasson, a Swedish addiction specialist, noticed that the schizophrenic patients who relapsed after being treated and released from the Karolinska Institute in Stockholm were often the ones who used cannabis. In an effort to determine the directionality of this association with marijuana, he conducted a retrospective study based upon data collected by the Swedish military draft. Questionnaires completed at intake by draftees were collected without personal identifiers. Of the nearly 50,000 recruits aged 18 – 19 years between 1968 and 1983, 92% had included information on their drug use. Since Sweden also had data on all hospitalizations for schizophrenia, Andreasson worked with statisticians to evaluate the outcome of 45,570 conscripts who were followed for 15 years. By 1983, 246 (0.54%) had been diagnosed with schizophrenia. Significantly, of 702 who had only used marijuana 10 to 50  times, there were 10 cases of schizophrenia (1.4% – three times the risk of nonusers). Of the 752 who had smoked more than 50 times by age eighteen, 21 had received the diagnosis – a risk of 2.8% or six times the risk of those who had never used marijuana.³⁹  A subsequent smaller study by the same author confirmed these findings.⁴⁰  More recently, they reported not only was cannabis use associated with increased frequency of schizophrenia but also with worse prognosis.⁴¹  Specifically, among individuals diagnosed with schizophrenia those with a history of cannabis use had more hospital readmissions and total hospital days compared to those without a history of cannabis use.

In 2023 Hjorthoj et al⁴² in Denmark “examined 6,907,859 individuals with 45,327 cases of incident schizophrenia during follow-up across 129,521,260 person-years. The overall adjusted HR (aHR) for cannabis use disorder (CUD) on schizophrenia was slightly higher among males (aHR = 2.42, 95% CI 2.33–2.52) than females (aHR = 2.02, 95% CI 1.89–2.17); however, among 16–20-year-olds, the adjusted incident risk ratio (aIRR) for males was more than twice that for females (males: aIRR = 3.84, 95% CI 3.43–4.29; females: aIRR = 1.81, 95% CI 1.53–2.15)” They concluded that young males were “particularly susceptible to the effects of cannabis on schizophrenia” and that “one-fifth of the cases of schizophrenia among young males might be prevented by averting cannabis use disorder.”In addition to schizophrenia, this same research  group⁴³ reported that “cannabis use disorder was associated with an increased risk of unipolar depression (HR, 1.84; 95% CI, 1.78-1.90), psychotic unipolar depression (HR, 1.97; 95% CI, 1.73-2.25), and nonpsychotic unipolar depression (HR, 1.83; 95% CI, 1.77-1.89),” an “increased risk of bipolar disorder in men (HR, 2.96; 95% CI, 2.73-3.21) and women (HR, 2.54; 95% CI, 2.31-2.80), psychotic bipolar disorder (HR, 4.05; 95% CI, 3.52-4.65), and nonpsychotic bipolar disorder in men (HR, 2.96; 95% CI, 2.73-3.21) and women (HR, 2.60; 95% CI, 2.36-2.85). Cannabis use disorder was associated with higher risk for psychotic than nonpsychotic subtypes of bipolar disorder (relative HR, 1.48; 95% CI, 1.21-1.81) but not unipolar depression (relative HR, 1.08; 95% CI, 0.92-1.27).”

A 2023 review article of 24 studies of recreational marijuana use found “a positive association between cannabis use and suicidal ideation and attempt among the general population, military veterans, and bipolar or major depression patients.”⁴⁴ Importantly, a younger age of initiation, along with longer term and heavier use, was associated with worse suicidal outcomes.

Myran et al studied the effect of marijuana legalization on mental illness in Ontario.  They found that 0.7% of 13 million individuals without cannabis use disorder developed schizophrenia while 8.9% of individuals with cannabis use disorder did so.⁴⁵  Furthermore the population attributable risk factor for cannabis use disorder with schizophrenia tripled post legalization from 3.7 % to 10.3% with the worst effect in males aged 19 to 24 years.  Similar effects were seen for non-specified psychosis.  This study clearly demonstrates the risks of legalization on mental health.

Marijuana and Physical Health

Respiratory and Cardiovascular Effects: Since marijuana contains many of the same compounds as tobacco, it has some of the  same adverse effects on the respiratory system when smoked as tobacco, although there are differences due to the presence of THC which may have bronchodilator effect.⁴⁴  Symptoms include chronic cough, wheezing, and shortness of breath.  Respiratory infections, bronchitis, and eventually emphysema may also be seen.⁴⁶ Vaping cannabis may reduce these symptoms.

Cardiovascularly, marijuana use increases catecholamines, cardiac workload, and carboxyhemoglobin levels which lead to postural hypotension and which may lead to an increased risk of myocardial infarction. Arrhythmias such as atrial fibrillation and fatal ventricular arrhythmias have also been attributed to marijuana use. “Cannabis arteritis” is a peripheral vascular consequence  that causes progressive ischemia of distal upper and lower extremities leading to tissue necrosis and gangrene.  Strokes and transient ischemic attacks following marijuana use have been reported.⁴⁶  A 2025 systematic review and meta-analysis found significant increases in relative risk for acute coronary syndrome (RR=1.29), stroke (RR=1.2) and cardiovascular death (RR=2.10).⁴⁷

A large study from Ontario comparing emergency room visits for respiratory concerns, other concerns, and mortality between cannabis users and non-users found no difference in visits for respiratory concerns but did find higher overall emergency room visits and morbidity in users.⁴⁸ A broader Canadian Study found higher 5-year mortality rates following an emergency department visit for cannabis use disorder.⁴⁹

Marijuana and Cancer: Chronic smoking of marijuana and its active chemical THC has consistently been shown to increase the risk of developing testicular cancer, particularly a more aggressive form of the disease. One study compared 369 Seattle-area men aged 18-44 with testicular cancer, to 979 men in the same age bracket without the disease. The researchers found that current marijuana users were 1.7 times more likely to develop testicular cancer than nonusers, and that the younger the age of initiation (below 18) and the heavier the use, the greater the risk of developing testicular cancer.^50,51 A similar study of 455 men in Los Angeles found that men with testicular germ cell tumors were twice as likely to have used marijuana as men without these tumors.⁵²

The relationship of smoking marijuana to lung cancer is less clear.  Significant precancerous changes have been demonstrated in the lungs of marijuana smokers but epidemiologic studies have found conflicting results with some showing increased lung cancer and others no difference.⁴⁶

In a 2023 study of substance related carcinogenesis in Europe, Reece et al demonstrated that cannabis should be considered a more potent carcinogen than either tobacco or alcohol.⁵³ Cannabis related cancers included skin, bladder, brain, breast, cervix, colorectum, Hodgkin’s, kidney, larynx, myeloid and lymphoid leukemias, liver, lung, melanoma, myeloma, non-Hodgkin’s lymphoma, esophagus, oropharyngeal tumors both broadly and narrowly defined, ovary, pancreas, prostate, stomach, testis and thyroid cancer.

Marijuana and Pregnancy: Public views regarding marijuana use during pregnancy are varied with as many as 20% perceiving no risk. Most individuals relied on the internet, friends, family community members or cannabis providers  for information with few relying on health care professionals.⁵⁴ Some even deliberately use cannabis for its perceived benefit.⁵⁴ However, a systematic review by Ainiti et al found that the children of mothers who used marijuana had disordered sleep cycles, memory problems, hyperactivity, increased rates of low birth weight and prematurity.⁵⁵ Apgar scores at 1 and 5 minutes were lower in children whose mothers used cannabis and there was increased neonatal intensive care use and shorter breast feeding. At age 18 months, exposed girls had more aggressive behavior.  Interestingly, gestational exposure to marijuana or alcohol leads to prolonged marijuana use during adolescence and young adulthood even when controlling for other factors.⁵⁶

Marijuana and the Pediatrician 

The data clearly indicates, despite public perception, that marijuana poses multiple  short-term and long-term risks to the mental and physical health of pediatric and adolescent patients.  Caregivers must be able to dispense accurate and appropriate information to patients and their parents based on accurate scientific studies and not based on the inaccurate or incomplete information present throughout lay sources.  Yet, the literature consistently shows that most physicians, including pediatricians, do not have adequate knowledge about marijuana.^57,58 

Skinner et al conducted focus groups with adolescents and parents to determine what type of information adolescents wanted and how it should be given.⁵⁹ They found that teens clearly felt they needed more information, and that information should focus on three general categories: messages providing information about the law and consequences of use, messages offering general advice to parents and youth, and messages with an explicit prevention focus, such as providing alternative positive activities.  Both parents and teens felt it was important to discuss negative consequences of use, although teens were resistant to “scare tactics.” Both groups felt having other activities would help avoid use and that it was important to have future goals and knowledge of how marijuana use could affect these goals.  Parents were generally thought to be an important source of information by the teens, but this was dependent on how the teens perceived the parental relationship.  Other studies have demonstrated that parental involvement helps avoid marijuana use⁶⁰ and lack of parental attachment can increase risk of use of marijuana and other substances.⁶¹ Low levels of parent-child communication are associated with increased marijuana use,⁶² while frequent family dinners are associated with decreased use.⁶³

Beyond this, pediatricians need to be able to recognize adolescents and teens with problematic cannabis use and know how to get them appropriate help.  Programs involving cognitive behavioral psychotherapies with family-based models, skills training, motivational interviewing have demonstrated the best results.¹⁹

CONCLUSION

Clear and convincing evidence exists that cannabis use is harmful, especially for adolescents and for pregnant women and their children.  It is neither beneficial nor benign.  Consequently, the ACPeds encourages pediatricians to give anticipatory guidance to the parents of pre-teens and teens regarding the risks of marijuana and encourages them to share this information with their child on an ongoing basis.  Parents should be encouraged to stay involved with their teens’ lives and activities and to have regular family interaction at the family table.  In addition, pediatricians should speak to legislators and the public regarding the risks of marijuana and the dangers of legalization.

Original Author (January 2007):
Don Hagler, MD, FCP

Revised (June 2020):
Don Hagler, MD, FCP
Jane Anderson, MD, FCP

Revised (October 2025):
Robert Hoffman, MD, FCP

The American College of Pediatricians is a national medical association of licensed physicians and healthcare professionals who specialize in the care of infants, children, and adolescents. The mission of ACPeds is to enable all children to reach their optimal, physical and emotional health and well-being.

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