A Review of the Effects of Adolescent Cannabis Use on Physical Health

INTRODUCTION

Adolescence is a time marked by various physical, psychological, and social changes, typically including initiation of substance use such as cannabis.^1–3 Increasing evidence suggests that cannabis use is not harmless, especially during periods of critical development.^4–6 As laws change around recreational and medical use of cannabis, prevalence of use in certain populations has changed too. Overall, prevalence of adult cannabis use has increased, whereas prevalence of adolescent use has seemed to remain steady or even decrease.^4,7–10 However, most of the studies that examined the impact of recreational and medical cannabis legalization on adolescent cannabis use do not consider frequency of use and/or potency of products that may have increased among adolescents. Nonetheless, cannabis use is still widespread among adolescents, with greater than 10% of 8th graders and greater than 35% of 12th graders endorsing use in the past year.¹⁰ The substantial portion of adolescents reporting cannabis use illuminates the need for further research into possible adverse health risks. Most of the research focused on this topic has been conducted with adults, with some newer adolescent studies emerging in the last decade.^11–14 This review outlines the current research on how cannabis use affects physical health in adolescence.

Smoking cannabis seems to be the most frequent method of use by adolescents, but vaping may be gaining popularity.^10,15 Results from the 2020 Monitoring the Future survey show that in eighth grade students there was a small increase in vaping cannabis. This trend was not observed in 10th and 12th grade students. However, in 2018 and 2019, increases in vaping both cannabis and nicotine were observed in all these age groups. Overall, 2020 rates for cannabis vaping annually were 8.1%, 19.1%, and 22.1%, for students in 8th, 10th, and 12th grade, respectively.¹⁰ Other recent, large studies have found similar levels of cannabis vaping in adolescents.^16,17 Concentrates, or high-potency cannabis products, are also gaining popularity among adolescents, 72% of adolescents who endorse cannabis use report using concentrates at least once in their lifetime.¹⁸

After changes in medical and recreational cannabis legalization in various states across the United States, concerns around adolescents having greater access to cannabis has driven research into possible changes and differences in adolescent use in legal versus nonlegal states.^4,9,19–21 Most of the studies focused on adolescent cannabis use patterns in medically legal states have not found any significant differences in adolescent use prevalence compared to nonmedically legal states.^21–23 However, one study did observe an increase in first-time adolescent cannabis use in medically legal states but not a subsequent increase in regular use.²² Another study did detect an increased rate of cannabis use in adolescents living in medically legal versus nonlegal states but highlighted that even before legalization, these now medically legal states had higher levels of adolescent use compared to non legal states.²⁴ Less research has been conducted on recreational cannabis legality and subsequent adolescent use, as these laws have been passed more recently, and there is little conclusive evidence to support any effect at this time.^9,19

This review includes research about the associations between cannabis use and indicators of physical health. The authors include studies addressing the association between cannabis use and pulmonary, cardiovascular, gastrointestinal, and endocrine function, as well as body mass index (BMI) and sleep. Table 1 provides an overview of clinical concerns for each of the body systems/constructs for adolescents who use cannabis. One major limitation of this research review is that most of this research has been conducted with adults rather than adolescents.

Table 1.

Physical health clinical concerns for adolescent who use cannabis

System/Construct	Clinical Concern
Pulmonary	• E-cigarette or vaping product use–associated lung injury (EVALI)
Cardiovascular	• Acute cardiovascular events (eg, myocardial infarction, atrial fibrillation, acute coronary syndromes [stroke], ventricular tachycardia, and sudden death)
Gastrointestinal	• Cannabinoid hyperemesis syndrome (CHS) • Nausea, stomach pain, and appetite loss during cannabis withdrawal
Endocrine	• Disruption of normal cortisol function throughout the day • Decreased stress reactivity
Body mass index (BMI)	• Lower BMI
Sleep	• Insomnia • Insufficient sleep on school nights • Shorter total sleep time • Later bedtimes • Evening chronotype

PULMONARY FUNCTION

The most common method of cannabis intake for adolescents is smoking.¹⁵ Most research on the impact of cannabis use on pulmonary function has focused on comparing the effects of cannabis smoking to the effects of tobacco smoking, as tobacco smoking has known health risks that have been replicated in many studies.^25–30 Most of the existing literature on pulmonary function comes from adult studies.^12,27,31 These studies assess various aspects of pulmonary function, with an emphasis on respiratory symptoms, lung function, and pulmonary diseases and disorders.^{12,27,31–33} However, recent research is emerging on e-cigarette or vaping product use–associated lung injury (EVALI), with particular concern involving cases among adolescents and young adults.^34–36

Research on cannabis use and respiratory symptoms has identified associations between smoking cannabis and coughing, wheezing, shortness of breath, and sputum production. Higher rates of coughing, sputum production, and wheezing in adults who use cannabis compared to those who do not have been found in several studies, even when controlling for tobacco use.^29,32,33,37 Rates of these symptoms in those who use cannabis were comparable with those who use tobacco, with some studies finding a higher prevalence of these symptoms in those who use cannabis compared to those who use tobacco or finding that cannabis and tobacco co-use resulted in higher rates of these symptoms.^29,32,33

Existing literature on cannabis use and lung function relies on spirometry measures such as forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC). The ratio of FEV1 to FVC is used to measure lung function and progression of disease, especially chronic obstructive pulmonary disease (COPD), with lower ratios indicating more airflow obstruction.^38,39 Results from these studies have been inconclusive, with many reporting conflicting results for the effect of smoking cannabis on FEV1, FVC, and FEV1/FVC ratios.^{12,26–29,32,40} For example, Aldington and colleagues²⁶ (2007) found a dose-response association between amount of cannabis exposure and lower FEV1/FVC ratios. In contrast, Hancox and colleagues²⁷ (2010) found cannabis exposure to be associated with higher FVC measurements, but was not found to be associated with FEV1/FVC ratios. Future studies are needed to settle the debate on whether cannabis smoking negatively affects lung function.

Attention has been given to the potential for cannabis use to increase risk for pulmonary diseases and disorders, such as asthma, COPD, lung cancer, and severe bronchitis. So far, studies on this topic have only been conducted with adults.^{25,30,31,41,42} Newer research has shown support for an association between asthma and cannabis use, and a recent study reported that emerging adults who currently use cannabis had a 1.71 odds ratio for filling prescriptions for asthma, even after controlling for relevant covariates such as BMI and tobacco use.^30,31 Studies that support an association between cannabis use and COPD are limited, but there is compelling research evidence to support an increased risk for severe or chronic bronchitis in those who use cannabis.^30,42–44 Finally, early research on cannabis smoking and risk of lung cancer has found some support for a possible association but has not yielded any conclusive results yet.^25,40,41,43 However, a recent, large-scale, longitudinal study investigating this association has found that adults who chronically use cannabis had an increased risk for lung cancer, suggesting that at high levels, cannabis smoking may have serious long-term detrimental effects on the lungs.⁴¹

Of the possible pulmonary-related effects of adolescent cannabis use, perhaps the most immediately concerning is the incidence of EVALI. With greater than 15% of EVALI cases occurring in adolescents, and 37.2% of adolescents in the Monitoring the Future 2020 survey reporting vaping, this issue is critically important, even though cases are not as high as they were during the initial EVALI outbreak in 2019.^10,34–36 Thakrar and colleagues³⁶ (2020) conducted a review of 12 adolescent EVALI cases and found that 100% of the patients had confluent ground-glass opacities and 92% had centrilobular ground-glass nodules present in their chest computed tomography scans. Other commonly occurring pulmonary effects of EVALI include respiratory symptoms such as shortness of breath, pain in the chest, cough, and more rarely, hemoptysis.^45,46 The median age of individuals who died as a result of EVALI was 51 years old, but the youngest recorded was 15 years old.⁴⁷ Texas and Illinois have the highest number of EVALI cases, and nonregulated delta-9-tetrahydrocannabinol (THC)-containing vaping products are more likely to result in injury compared to products that do not contain THC.^34,45

CARDIOVASCULAR FUNCTION

The impact of cannabis use on cardiovascular health is unclear because research has reported mixed results. Most research of cannabis use and cardiovascular function have focused on heart rate and blood pressure; thus this section focuses on those 2 outcomes as well. However, no studies have examined the impact of cannabis use on heart rate and blood pressure in a sample of adolescents.

Most research on the impact of cannabis use on heart rate has focused on acute effects. All research suggest that acute cannabis intoxication is associated with an increased heart rate.^48,49 Furthermore, one randomized controlled trial of cannabis use found that smoked cannabis was associated with an increased heart rate, and the feeling of being “high” was positively associated with heart rate. Heart rate peaked after 10 minutes of smoking cannabis and the increased heart rate went down to pre-use levels after 40 minutes.⁴⁹ Another study of acute cannabis intoxication found that after smoking cannabis, heart rate and salivary THC levels were positively associated.⁴⁸ However, both samples include less than 15 participants, so substantial conclusions about the association between heart rate and acute cannabis intoxication cannot be made. Although rare, a series of case reports have found that there are documented deaths of young adults from acute cardiovascular events after recently ingesting cannabis.⁵⁰ Although rare, myocardial infarction can occur within 60 minutes of ingesting cannabis.⁵¹ Furthermore, other cardiovascular events have been found following cannabis ingestion including atrial fibrillation, acute coronary syndromes (such as stroke), ventricular tachycardia, and even sudden death. These effects were found in young patients without any other risk factors for cardiovascular events.⁵² The long-term effects of cannabis use on heart rate are less clear. One study examined 72 men who tested positive for THC and 72 matched controls and found that heart rate variability was higher among those who tested positive for THC compared to controls.⁵³ However, a recent co-twin control study found that cannabis frequency was negatively associated with resting heart rate finding that more frequent cannabis use was associated with a lower resting heart rate.⁵⁴

Acutely, cannabis use is associated with reduced blood pressure but this has only been documented in animal studies.⁵⁵ Long-term effects are also unclear. One study that included more than 12,000 adults reported a positive dose-dependent association between past 30-day cannabis use and systolic blood pressure. Each additional day of cannabis use was associated with increased 0.10 mmHG in systolic blood pressure; however, the clinical significance of this increase is unclear.⁵⁶ Two additional studies found that cannabis use, measured in joint-years, was associated with lower systolic and diastolic blood pressure among adults.^57,58 One co-twin control study did not find evidence of a causal association between cannabis frequency and systolic or diastolic blood pressure.⁵⁴ Finally, several studies have examined what happens to blood pressure during cannabis cessation, finding no significant change in blood pressure,⁵⁹ whereas one small crossover study found increases in blood pressure during cannabis cessation.⁶⁰

GASTROINTESTINAL FUNCTION

The current research focused on cannabis use, and gastrointestinal function includes cannabinoid hyperemesis syndrome, cannabis withdrawal syndrome, and the medicinal use of cannabis for treating digestive disorders such as inflammatory bowel disease.^13,61–63 Most of these studies include only adults rather than adolescents or are limited by small sample sizes.^64–67 Few studies address specific cannabinoids (CBD) in their analyses on the effect of cannabis on gastrointestinal function. However, there is research about the potential for CBD to treat digestive disorder symptoms, but this research has yielded inconclusive findings.^68–70

Cannabinoid hyperemesis syndrome (CHS) is characterized by frequent, repeated episodes of cyclic vomiting in individuals who chronically use cannabis.^13,71 The current literature on CHS relies almost entirely on case studies, and therefore, little is known about the prevalence or potential risk factors (eg, using high-potency cannabis or method of cannabis intake) for developing the syndrome.^72–74 The largest case series on CHS found that the average age of onset of symptoms was 25.3 years.¹³ One study assessing self-reported symptoms of the syndrome in a sample of adult patients presenting to the emergency department and who also endorse currently using cannabis more than20 times per month found that 32.9% of those who used cannabis frequently met diagnostic criteria for CHS.⁷⁵ The incidence of CHS cases in emergency departments in Colorado has increased by almost 2-fold since legalization of recreational cannabis.^72,76

The pathophysiology of CHS is unknown and still being investigated by researchers.^65,67 The Rome IV is the most recently updated tool for diagnosing CHS and was designed for use in adults.⁷⁷ An interesting clinical feature of CHS observed frequently in patients is a pattern of excessive bathing. The bathing is reported to provide relief from cyclic vomiting, and patients with CHS often spend a great deal of time seeking this relief.^13,65 Sorensen and colleagues⁶⁶ (2017) conducted a systematic review of the current literature on CHS in adults and found that 92.3% of all participants endorsed excessive bathing for relief. Weight loss also seems to be associated with CHS in some studies, although this symptom is not as commonly reported as excessive bathing.^13,67,71 The current research on CHS is mainly focused on describing the symptoms of the syndrome and possible treatments. At present, the most successful treatment is complete cessation from cannabis use, and more research is needed to determine the degree of abstinence needed to ensure continued recovery.^13,65,71

Cannabis withdrawal syndrome occurs after cessation of cannabis use among some who use cannabis regularly. The syndrome can be diagnosed using a 15- or 22-item checklist derived from the Cannabis Withdrawal Checklist, created by Budney in 1999.^78–80 Cannabis withdrawal is marked by a wide array of physical and psychological symptoms such as anxiety, insomnia, and sweating, but most relevant to gastrointestinal function are the symptoms of nausea, stomach pain, and appetite loss. The existing literature on the topic supports the fact that women are more likely to experience these gastrointestinal-related symptoms than men.^61,63

Finally, cannabis has been studied as a potential treatment of digestive disorders. Self-reported data support that there are individuals with inflammatory bowel disease (IBD) who have tried cannabis as a treatment and report relief from symptoms such as nausea and appetite loss.^64,68 Researchers posit that the antiinflammatory effects of cannabis are likely responsible for the symptom relief reported from cannabis use through the interaction between cannabis and the endocannabinoid system, which has receptors present across the gastrointestinal system.^81–83 Most of the research on cannabis as a treatment of IBD comes from adults; however, Hoffenberg and colleagues⁶² (2019) investigated the use of cannabis oil in adolescents and young adults with IBD, also finding support for cannabis oil relieving these symptoms. This topic is still largely under investigation, and there are very few clinical trials to support cannabis as a useful treatment of gastrointestinal disorders. The existing clinical trials support that cannabis is tolerated by patients but do not conclude that it is an effective treatment of these disorders.^{68–70,84,85}

ENDOCRINE FUNCTION

The existing literature focused on the effects of cannabis use on hormone function focuses almost exclusively on adults and predominantly on fertility, sexual function, hunger hormones, thyroid function, and psychobiological aspects of stress.^11,86–93 Some studies have shown that cannabis use may affect hormone levels involved in various important endocrine systems, including the hypothalamic-pituitary-adrenal (HPA) axis.^86,94 Although adolescent-focused research on this topic is scarce, increasing attention has been given to the possible effect of cannabis on pubertal timing and tempo in adolescents, informed by animal studies conducted in the 1980s and 1990s. Specifically, animal data support that prepubertal exposure to cannabis is associated with pubertal delays in women and decreases in pubertal growth spurts in men.^92,95–98

The research focused on the effect of cannabis use on fertility and sexual function focuses heavily on men, with little conclusive evidence on women.^{88–91,93,99–101} Some studies on women suggest that fertility may be decreased by cannabis use, whereas other studies have refuted any effect of cannabis on female fertility.^89,91,93,99 The current literature on the fertility and sexual function of adult men who use cannabis shows a tendency for those who used to have lower sperm counts and lower sperm concentrations compared to those who do not use cannabis.^88,90 Studies on the effect of cannabis on testosterone have mixed results, as some support heightened testosterone levels in men who use cannabis, some have seen no effects, and some support lower testosterone levels compared to men who do not use cannabis.^{88,90,100,101}

Few studies have investigated the effect of cannabis use on thyroid function in humans. Existing studies have been conducted with adults, using biological measures to assess levels of the thyroid-stimulating hormone (TSH).^11,102,103 The primary role of TSH is to stimulate the thyroid gland to release triiodothyronine (T3) and thyroxine (T4). Abnormal levels of these hormones can lead to metabolic dysfunction or disease, such as hyperthyroidism and hypothyroidism.¹⁰⁴ Two well-designed studies pertaining to cannabis use and thyroid function were identified from the current literature and results from these studies are mixed. Bonnet (2013)¹⁰² found no significant differences in thyroid hormone levels between adults who use cannabis compared to those who do not, whereas Malhotra and colleagues¹¹ (2017) found lower levels of TSH among those who use cannabis compared to those who do not. There is no evidence to support that cannabis use is associated with thyroid dysfunction at this time, but the early findings supporting the potential ability of cannabis to affect levels of key hormones such as TSH suggest more research is needed to confirm this.¹¹

Cannabis has been shown to acutely increase appetite,^105,106 but research related to cannabis use and hunger hormones is limited. All empirical human studies on this topic use samples of adults and focus chiefly on insulin, ghrelin, leptin, peptide YY, and glucagon-like peptide 1.^87,107 Farokhnia and colleagues (2020) conducted a randomized, placebo-controlled trial of the effect of cannabis ingestion on various hunger-related hormones, accounting for different routes of cannabis administration. Their study found that compared to placebo, cannabis intake was associated with a decrease in the normal and expected insulin spike following sugar intake. They also found support for decreased levels of glucagon-like peptide 1. An increase in levels of ghrelin was observed, but only following oral cannabis intake.⁸⁷ Glucagon-like peptide 1 is necessary for decreasing appetite after eating, so lower levels may disrupt the body’s ability to feel satiated.^108,109 Ghrelin, in contrast, is responsible for stimulating appetite, and it is logical that cannabis would appear to decrease appetite suppressing hormones and increase appetite stimulating hormones, as a substance known to increase appetite in the short-term.⁸⁷ One study among rats confirmed that cannabis use is associated with increasing ghrelin levels.¹¹⁰

Some of the most compelling findings pertaining to endocrine function and cannabis use come from studies on the effect of cannabis on stress hormones and the HPA axis. The HPA axis is responsible for the physiological response to stress, and dysfunction in the HPA axis can have negative consequences for physical and emotional health.^14,86,94,111 Few studies had samples of adolescents, and studies that had adolescent samples were either animal studies or clinical samples, such as adolescents who are at-risk for psychosis.^111,112 However, findings from a nonclinical cohort study of adolescents, the TRacking Adolescents’ Individual Lives Survey (TRAILS) study, have yielded interesting results pertaining to stress reactivity and cannabis use.^14,113 Results from the TRAILS study show a tendency for decreased stress reactivity in adolescents with lifetime cannabis use compared to those who had never used cannabis, while controlling for sociodemographic contributors to stress.¹⁴ The TRAILS study has also found that adolescents with early onset cannabis use had lower cortisol levels after waking compared to adolescents who have never used cannabis or initiated use later. In contrast, they found support for higher cortisol levels in the evening among those who endorse using cannabis at least once in their lifetime compared to those who have never used cannabis; this suggests that adolescent cannabis use, and particularly earlier initiation, may disrupt the normal cortisol fluctuations experienced throughout the day.¹¹³ Early onset was defined as cannabis use onset between ages 9 and 12 years and later onset between ages 13 and 14 years.¹¹³ Empirical studies addressing the use of cannabis on both psychological and physiological aspects of stress have been conducted with adults and have found a dampened stress response among those who use, even after periods of abstinence.^86,94 Data from adults have also shown that those who currently use cannabis compared to those who do not have elevated baseline levels of cortisol and adrenocorticotropic hormone compared to those who have never used cannabis, with the highest levels observed in those who currently use.⁸⁶ The observed effects of decreased stress responsiveness and general heightened stress hormone levels in these studies may show a potentially problematic effect of cannabis use on everyday functioning, but this has been refuted by some studies, suggesting that more research needs to be conducted on this topic.^114,115

BODY MASS INDEX

Children and adolescents who are obese are more likely to have high blood pressure and cholesterol,¹¹⁶ breathing problems including asthma,¹¹⁷ sleep apnea,¹¹⁸ and an increased risk of type 2 diabetes.¹¹⁹ Thus, understanding factors that contribute to BMI in children and adolescents is an important public health issue. In particular, acute intoxication of cannabis is associated with appetite stimulation and increased caloric intake.^105,106 However, the long-term effects of cannabis use on BMI among adolescents is less clear. Results among the few studies that have been conducted on the association between these variables is mixed. Several studies have found no association between these variables,^120–122 whereas one study found that increased cannabis use during adolescence is associated with increased risk of obesity in young adulthood.¹²³ Another cross-sectional study found that more frequent cannabis use is associated with a higher BMI and greater likelihood of being classified as overweight or obese.¹²⁴ However, in the same sample of adolescents an increase in cannabis use was associated with a decrease in BMI.¹²⁵ The association between cannabis use and BMI has been more extensively studied among adults compared to adolescents.

Similar to the research among adolescents, studies among adults have generally reported mixed findings. For example, some research has suggested there is no association between cannabis use and BMI,^126–129 whereas other studies report a positive association between cannabis use with BMI,^124,130 abdominal fat,¹³¹ and metabolic syndrome.¹³² However, most of the studies on this topic have found a negative association between cannabis use and BMI when comparing those who use cannabis to those who do not^133–135 and when examining dose-dependent associations.^{57,58,125,136} Furthermore, other factors related to BMI are also associated with cannabis use, such as lower rates and risk factors for diabetes,^135,137,138 lower likelihood of cardiometabolic diagnoses,^58,139 and smaller waist circumference.¹³⁵ Other factors related to BMI such as diet and exercise engagement may help explain the association between cannabis use and BMI.

Although cannabis use among adults is most consistently associated with a lower BMI, those who use cannabis tend to report a higher caloric intake,¹⁴⁰ a lower diet quality,¹⁴¹ and engaging in more unhealthy weight control behaviors such as skipping meals.¹⁴² Adults who endorsed past month cannabis use reported eating fewer vegetables and fruits compared to those who have never used or used previously. However, adults who currently use cannabis reported eating less sodium and refined grains compared to those who have never used cannabis.¹⁴¹ In a prior study from 2001, those who currently use cannabis reported higher sodium intake, eating fewer fruits, and eating more salty snacks. Furthermore, those who currently use reported a higher caloric intake but still had a lower BMI.¹⁴³ In regard to exercise, adults who currently or previously used cannabis are more likely to report meeting recommended levels of exercise compared to those who have never used cannabis.¹⁴⁴ In addition, in one study of adults who currently use cannabis, around 80% reported using cannabis shortly before or after physical activity and these individuals reported engaging in aerobic and anerobic exercise for longer and reported greater enjoyment from exercising compared to those who do not use cannabis concurrently with exercise.¹⁴⁵ In line with the adult literature, one study among adolescents reported a positive association between frequency of cannabis use and greater exercise engagement.¹⁴⁶

More research, particularly among adolescent samples, is needed on this topic to better understand the mechanisms through which cannabis use affects BMI. More evidence suggests that the endocannabinoid system, which contains cannabinoid type 1 (CB1) receptors and endogenous ligands, is likely involved with appetite. Δ9-THC is the primary psychoactive compound in cannabis and is a partial agonist of the CB1 receptor. Thus, a drug, Rimonabant, was developed to decrease appetite among obese individuals, acting as a selective antagonist/inverse agonist of the CB1 receptor. Rimonabant was an effective weight loss drug; however, it was denied approval by the Food and Drug Administration because of severe psychiatric side effects.¹⁴⁷ In summary, cannabis use is associated with a lower BMI,^{57,58,125,133–136} poorer diet such as eating fewer vegetables and fruits,^140–143 and higher levels of exercise engagement.^144,145 However, more research is needed among adolescents to understand if these associations are present earlier in life and the mechanisms through which cannabis use acts on these factors.

SLEEP

Sleep is an important aspect of adolescent development, playing a crucial role in physiology, cognition, and mental health.^148,149 The endocannabinoid system is thought to be involved in the modulation of circadian rhythm and the sleep/wake cycle,^150,151 particularly through the influence of cannabinoids on CB1 receptors.^152,153 Heavy cannabis activity is linked to desensitization, and decreased CB1 efficacy^154,155 and blocking of the CB1 receptors have been found to facilitate waking in rodent models specifically.^156,157 There is limited evidence to suggest that cannabis use might influence aspects of the sleep cycle such as slow-wave sleep (SWS)^158–160 and rapid eye movement sleep.^161,162 Although cannabis is often thought to be a sleep aid¹⁶³ and there is evidence of acute cannabis use being linked to temporary sleep benefits, research implies that consistent and increased frequency of cannabis use in general is associated with sleep deficits and sleep pathology across multiple domains.^163,164

Most existing research has been conducted in adult populations, but cross-sectional studies focused on adolescent cannabis use have found associations with various sleep factors including insomnia (defined as trouble falling asleep or staying asleep almost every day),¹⁶⁵ insufficient sleep on school nights,^166,167 shorter total sleep time, later bedtimes,¹⁶⁸ greater endorsement of past month sleep problems (eg, waking up several times per night and waking up feeling tired and worn out),¹⁶⁹ an evening chronotype (a preference for later sleep-wake timing),¹⁷⁰ and modest sleep architecture alterations at the onset of abstinence (lower percent SWS).¹⁷¹ One study found differential effects with an association at baseline (mean age 15 years) between cannabis use and weekend oversleep, but an opposite relationship at follow-up (mean age 17 years) between cannabis use and lower weekend sleep duration.¹⁷² Interestingly, we see a bidirectional association between these domains, with both early sleep problems and an evening chronotype predicting later cannabis use outcomes,^170,173,174 and earlier age of cannabis use behaviors predicting later sleep deficits and pathology such as worse sleep quality,¹⁷⁵ shorter sleep duration,^176,177 insomnia, and insomnia with short sleep.¹⁷⁸ One study found more complex associations, with higher levels of baseline weekday, and total sleep (mean age 15 years) predicted lower levels of cannabis use at a 2-year follow-up (mean age 17 years), whereas cannabis use at baseline predicted more weekend sleep, greater weekend oversleep, and higher total sleep at follow-up.¹²²

With both cross-sectional and bidirectional associations, a common liability such as shared genetics could explain these associations,¹⁷⁷ such that the genes that contribute to cannabis use behaviors also contribute to sleep deficits (or vice versa). Evidence of an association in both directions could also be rooted in differing developmental processes. Prenatal cannabis exposure has been associated with child sleep outcomes across development. Significant differences have been found in irregular sleep, sleep-related body movements,¹⁷⁹ and abnormal sleep wake cycles days after birth.¹⁸⁰ Effects later in life have been noted, including increased nocturnal arousals, greater awake time after sleep onset, and lower sleep efficiency at age 3 years,¹⁸¹ as well as increased endorsement of symptoms of sleep wake disorders, disorders of initiating and maintaining sleep, disorders of arousal, disorders of excessive somnolence, and higher sleep disorder scores at ages 9 to 10 years.¹⁸² The fetal brain is densely populated with CB1 receptors that escalate in activity during gestation and are believed to affect brain development.^183,184 It is possible that early cannabis use or exposure could affect sleep via CB1 receptors. However, early sleep issues could lead to emotional dysregulation and cognitive deficits that could increase susceptibility to substance use and in turn lead to more sleep issues.¹⁸⁵

Nevertheless, the complexities of this association are yet to be understood and research regarding cannabis use and adolescent sleep outcomes remains understudied. There are no studies to date looking specifically at the effects of CBD and THC on adolescent sleep. Research in adult populations suggest that CBD and THC have differential effects on sleep outcomes depending on the dosage. Broadly, high doses of CBD have been found to have sedating effects and low doses of CBD are associated with stimulating effects, whereas low-dose THC is thought to be sedating and high-dose/long-term THC seems to obstruct sleep.¹⁶⁴

SUMMARY

Prevalence of cannabis use is high among adolescents. Daily use of cannabis was at its highest level in 2020 compared to the past 30 years, with 1.1%, 4.4%, and 6.9% of students in 8th, 10th, and 12th grade, respectively, reporting daily use of cannabis.¹⁰ In addition, perceived harmfulness of cannabis has decreased steadily since 1991 among adolescents.¹⁰ Furthermore, recreational and medical legalization has made cannabis more widely available across the United States among adolescents. Adolescence is a developmental period characterized by dramatic growth in physical and psychological health. As a result, it is imperative that we understand how cannabis use affects pulmonary, cardiovascular, gastrointestinal, and endocrine function and BMI and sleep during this critical developmental period.

There are some significant limitations in the current research on how cannabis use affects physical health among adolescents. Most research has primarily included adults. As a result, less is known about the physical health effects of cannabis use among adolescents. It would be important to understand how cannabis use affects the physical health of those who are already vulnerable to health issues, such as adolescents with asthma. In addition, research should focus on aspects of physical health most relevant to adolescents such as activities that involve greater cardiovascular and pulmonary strength (eg, sports and playing a wind instrument). From 1995 to 2014 in the United States, THC potency increased from 4% to 12% and the ratio of THC to CBD increased from 14:1 to 80:1 among cannabis products confiscated by law enforcement.¹⁸⁶ However, many people in the United States now have access to legal cannabis markets that offer high-potency cannabis concentrates that have THC levels greater than 90%. However, there is little to no research on the impact of differing cannabis potency on physical health. Perhaps results would differ in individuals using products with greater than 90% THC. In addition, there are different methods of cannabis consumption such as vaping and edibles as well as different cannabis compounds, and we do not have a good understanding of how these novel cannabis products may affect physical health among adolescents.

Overall, the extant literature suggests that cannabis use, and more frequent use, may have negative effects on physical health particularly in the domains of pulmonary function and sleep. Specifically, cannabis use is associated with coughing, wheezing, shortness of breath, and sputum production^29,32,33,37 as well as insomnia, later bedtimes, not enough sleep on school nights, and greater sleep problems.^165–169 It is less clear whether cannabis use in adolescence negatively affects diet or gastrointestinal, hormone, or cardiovascular function. Importantly, cannabis use does seem to have some rare, but serious and sometimes deadly, side effects that have been reported in adolescents and young adults. These side effects include CHS (ie, cyclic vomiting),^13,71 cardiovascular events sometimes leading to sudden death (eg, myocardial infarction, atrial fibrillation, ventricular tachycardia),^50–52 and acute lung injury leading to hospitalization and death.^45,187 More research is clearly needed to better understand how cannabis use may affect physical health during this vulnerable developmental period.

KEY POINTS.

• Adolescents who vape are at risk for e-cigarette or vaping product use–associated lung injury.

• Various case studies support that adolescents who use cannabis can develop cannabinoid hyperemesis syndrome.

• Cannabis use is associated with a lower body mass index among adolescents.

• Research is inconclusive on the impact of cannabis use on heart rate and blood pressure.

• Cannabis use among adolescents is associated with various sleep outcomes such as insomnia, shorter sleep time, later bedtimes, and greater endorsement of sleep problems.

CLINICS CARE POINTS.

• Adolescent cannabis use is associated with coughing, wheezing, shortness of breath, and sputum production and sleep problems.

• Adolescet cannabis use is associated with several rare but serious side effects:

  • Cannabinoid hypermesis syndrome (that is cyclic vomiting)
  • Cardiovascular events (such as myocardial infarction, atrial fibrilation, and ventricular tachycardia)
  • Acute lung injury (that is e-cigarette or vaping product use-associated lung injury)