Steven Wright, MD, FAAFP; Julius Metts, MD, FAAFP Recreational cannabinoid use: Private practice, Littleton, Colo (Dr. Wright); California Substance Abuse and The hazards behind the “high” Treatment Center, Department of Corrections and Marijuana use can cause concerning physical, Rehabilitation, Corcoran (Dr. Metts) psychomotor, cognitive, and psychiatric effects, [email protected] not to mention a near-doubling of car accidents. The authors reported no potential conflict of interest relevant to this article. pproximately 156 million Americans (49% of the PRACTICE population) have tried cannabis.1 About 5.7 million RECOMMENDATIONS people ages 12 years and older use it daily or almost ❯ Screen all patients A 2 daily, a number that has nearly doubled since 2006. There are for use of addiction- 6600 new users in the United States every day,2 and almost half prone substances. A of all high school students will have tried it by graduation.3 ❯ Screen cannabis users with There is limited evidence that cannabis may have medi- a validated secondary screen cal benefit in some circumstances.4 (See “Medical marijuana: for problematic use. A A treatment worth trying?” J Fam Pract. 2016;65:178-185 or ❯ Counsel patients that http://www.mdedge.com/jfponline/article/106836/medical- there is no evidence that use marijuana-treatment-worth-trying.) As a result, it is now legal of recreational cannabis is for medical purposes in 25 states. Recreational use by adults safe; advise them that it can is also legal in 4 states and the District of Columbia.5 The US cause numerous physical, Food and Drug Administration, however, has reaffirmed its psychomotor, cognitive, stance that marijuana is a Schedule I drug on the basis of and psychiatric effects. C its “high potential for abuse” and the absence of “currently Strength of recommendation (SOR) accepted medical uses.”6 A Good-quality patient-oriented The effects of legalizing the medical and recreational evidence use of cannabis for individuals—and society as a whole—are B Inconsistent or limited-quality patient-oriented evidence uncertain. Debate is ongoing about the risks, benefits, and C Consensus, usual practice, rights of individuals. Some argue it is safer than alcohol or that opinion, disease-oriented evidence, case series criminalization has been ineffective and even harmful. Others make the case for personal liberty and autonomy. Still, others are convinced legalization is a misdirected experiment that will result in diverse adverse outcomes. Regardless, it is important that primary care providers understand the ramifications of marijuana use. This evidence-based narrative highlights major negative consequences of non-medical cannabinoid use. Potential adverse consequences of cannabis use Although the potential adverse consequences are vast, the lit- erature on this subject is limited for various reasons: • Many studies are observational with a small sample size. 770 THE JOURNAL OF FAMILY PRACTICE | NOVEMBER 2016 | VOL 65, NO 11 TABLE 1 Quality of life, socioeconomic issues associated with recreational cannabis use Lower quality of life9 Poor school attendance10 Relationship problems9,10 Lower educational achievement9,10 Lower income, financial instability, greater welfare dependence9,10 More discipline problems11 Decreased work commitment, performance, success9-11 More youth involved in crime12 Increased work absenteeism, presenteeism10,11 More involvement with other illicit drugs12 • Most studies examine smoked canna- comastia, and changes in sexual function.17 bis—not other routes of delivery. Elevated rates of myocardial infarction, car- • When smoked, the dose, frequency, diomyopathy, limb arteritis, and stroke have duration, and smoking technique are been observed.18 Synthetic cannabinoids variable. have been associated with heart attacks and • The quantity of Δ-9-tetrahydrocanna- acute renal injury in youth;19,20 however, binol (THC), the primary psychoactive plant-based marijuana does not affect the component in cannabis, is variable. kidneys. In addition, high doses of plant- (For more on the chemical properties based marijuana can result in cannabinoid Cannabis users of the marijuana plant, see “Cannabi- hyperemesis syndrome, characterized by have a lower noids: A diverse group of chemicals”7 cyclic vomiting and compulsive bathing that body mass on page 773.) resolves with cessation of the drug.21 index, better • Most studies do not examine medi- ❚ No major pulmonary effects. Inter- lipid parameters, cal users, who are expected to use less estingly, cannabis does not appear to have and are less cannabis or lower doses of THC. major negative pulmonary effects. Acutely, likely to have • There are confounding effects of other smoking marijuana causes bronchodila- diabetes than drugs, notably tobacco, which is used tion.22 Chronic, low-level use over 20 years is their non-using by up to 90% of cannabis users.8 associated with an increase in forced expira- counterparts. tory volume in one second (FEV1), but this ❚ Lower quality of life. In general, regu- upward trend diminishes and may reverse lar non-medical cannabis use is associated in high-level users.23 Although higher lung with a lower quality of life and poorer socio- volumes are observed, cannabis does not economic outcomes (TABLE 1).9-12 Physical appear to contribute to the development of and mental health is ranked lower by heavy chronic obstructive pulmonary disease, but users as compared to extremely low users.9 can cause chronic bronchitis that resolves Some who attempt butane extraction of THC with smoking cessation.22 Chronic use has from the plant have experienced explosions also been tied to airway infection. Lastly, and severe burns.13 fungal growth has been found on marijuana Studies regarding cannabis use and plants, which is concerning because of the weight are conflicting. Appetite and weight potential to expose people to Aspergillus.22,24 may increase initially, and young adults ❚ Cannabis and cancer? The jury is out. who increase their use of the drug are more Cannabis contains at least 33 carcinogens25 likely to find themselves on an increasing and may be contaminated with pesticides,26 obesity trajectory.14 However, in an observa- but research about its relationship with can- tional study of nearly 11,000 participants ages cer is incomplete. Although smoking results in 20 to 59 years, cannabis users had a lower histopathologic changes of the bronchial mu- body mass index, better lipid parameters, cosa, evidence of lung cancer is mixed.22,25,27 and were less likely to have diabetes than Some studies have suggested associations non-using counterparts.15 with cancers of the brain, testis, prostate, and ❚ Elevated rates of MI. Chronic effects cervix,25,27 as well as certain rare cancers in may include oral health problems,16 gyne- children due to parental exposure.25,27 CONTINUED JFPONLINE.COM VOL 65, NO 11 | NOVEMBER 2016 | THE JOURNAL OF FAMILY PRACTICE 771 TABLE 2 Outcomes associated with cannabis use during pregnancy and/or breastfeeding Pediatric cancers: neuroblastoma, astrocytoma, Decreased attention, memory, cognitive function41,42 rhabdomyosarcoma, leukemia22,25 Birth defects (mixed data): anencephaly, gastroschisis, ventricular Decreased learning ability and educational attainment41,42 septal defects41 Decreased growth41 Increased impulsivity, behavior problems41,42 Neonatal cannabis withdrawal syndrome42 Increased risk of tobacco or cannabis initiation as adolescents42 There are conflicting data about assoc- few deaths and a greater number of hospi- iations with head and neck squamous cell talizations, due mainly to central nervous carcinoma,25,27,28 bladder cancer,25,29 and non- system effects including agitation, depres- Hodgkin’s lymphoma.25,30 Some studies sug- sion, coma, delirium, and toxic psychosis, gest marijuana offers protection against have been attributed to the use of synthetic Cannabis certain types of cancer. In fact, it appears that cannabinoids.20 contains at least some cannabinoids found in marijuana, such ❚ Cannabis use can pose a risk to the 33 carcinogens as cannabidiol (CBD), may be antineoplas- fetus. About 5% of pregnant women report and may be tic.31 The potential oncogenic effects of edible recent marijuana use2 for recreational or contaminated and topical cannabinoid products have not medical reasons (eg, morning sickness), and with pesticides. been investigated. there is concern about its effects on the devel- ❚ Use linked to car accidents. More oping fetus. Certain rare pediatric cancers22,25 recent work indicates cannabis use is asso- and birth defects41 have been reported with ciated with injuries in motor vehicle,32 non- cannabis use (TABLE 222,25,41,42). Neonatal with- traffic,33 and workplace34 settings. In fact, drawal is minor, if present at all.42 Moderate a meta-analysis found a near-doubling of evidence indicates prenatal and breastfeed- motor vehicle accidents with recent use.32 ing exposure can result in multiple devel- Risk is dose-dependent and heightened opmental problems, as well as an increased with alcohol.35-37 Psychomotor impairment likelihood of initiating tobacco and marijuana persists for at least 6 hours after smoking use as teens.41,42 cannabis,38 at least 10 hours after ingesting ❚ Cognitive effects of cannabis are a it,37 and may last up to 24 hours, as indicated concern. The central nervous system is not by a study involving pilots using a flight fully myelinated until the age of 18, and com- simulator.39 plete maturation continues beyond