Health Risks of Marijuana Usage


Twenty-three states and the District of Columbia have legalized marijuana to some degree. 4 states and the District of Columbia have made it legal for recreational use, and the trend toward more lenient laws continues. Despite popular culture, there are health risks to be aware of. Below are some of the health findings of the Colorado Department of Public Health and Environment’s (CDPHE) 2014: Monitoring Health Concerns Related to Marijuana in Colorado, Literature Review and other sources. These findings look at vulnerable populations closely and provide strong evidence from well-designed methodology, despite a clear paucity of population level data with regards to marijuana usage in the United States and abroad. 

Drs. Vasilis Vasiliou (YSPH) and Andrew Monte (CU- Denver) are preparing a new set of studies on the interactions between marijuana and alcohol usage. 

Credits: Dr. Vasilis Vasiliou, Dr. Andrew Monte, Hannah Kanneck, MPH ’16 (Department of Environmental Health Sciences) and Mike McLaughlin, PhD candidate (Department of Health Policy and Management). Special thanks to Michael Van Dyke and Lisa Barker of the Colorado Department of Public Health and Environment.

Marijuana Policy In Connecticut Now, and In the Future

Marijuana policy is particularly complex. While states such as Colorado and Washington have passed laws allowing marijuana to be purchased and used by all adults over 21, marijuana is still considered a Schedule I substance under the Drug Enforcement Agency’s Controlled Substances Schedule, and possession of marijuana is technically illegal under Federal law.

  • U.S. Code Title 21 Chapter 13 Subchapter I generally describes the controlled substance act and associated laws

In Connecticut, it is illegal to possess, sell, or use marijuana unless someone has registered with the state as part of its medical marijuana program.

The legal consequences for possession, sale, or use of marijuana vary based on the type of act committed, with differences in the penalties and severity of the charge associated with each act.

Connecticut is sometimes called a ‘decriminalized’ state, which means that individuals who are guilty of possession of relatively small amounts of marijuana are guilty of an infraction, which is similar to a parking ticket.  Other acts, such as selling marijuana or possession of larger (more than ½ of an ounce) amounts of marijuana are generally considered a criminal act and individuals may be charged with a misdemeanor or felony depending on the circumstances.

  • Connecticut State Statutes, Chapter 420b, Section 21a-240 (7) and 21a-279a cover decriminalization. Other sections cover penalties for other types of crimes.

Connecticut allows some individuals to possess and use marijuana for medical purposes. To qualify for medical marijuana a patient must be at least 18 years of age and a physician must state that the patient has a debilitating medical condition, and the physician must believe the patient could potentially benefit from palliative use of marijuana. A full list of debilitating medical conditions can be found at the following Connecticut Department of Consumer Protection Website: 

Some individuals can be designated as ’caregivers’. These are individuals who take on responsibility for managing the palliative use of marijuana for someone registered to use marijuana. For example, a patient may lack the physical capabilities to use marijuana without help. In these cases, a ‘caregiver’ may be designated to help this individual. 

Individuals who qualify for medical marijuana can purchase marijuana at a licensed marijuana dispensary. Dispensaries are businesses that are licensed by the Connecticut Department of Consumer Protection, and follow a set of regulations regarding how marijuana can be dispensed and who can own a dispensary.

Dispensaries receive marijuana from licensed producers. Similar to dispensaries, producers are licensed by the Connecticut Department of Consumer Protection. The Department of Consumer Protections also is responsible for many of the regulations regarding producers.

  • CT Public Act No 12-55, An Act Concerning the Palliative Use of Marijuana (

As of January 1, 2016. It is unclear whether Connecticut will also legalize the use of marijuana, similar to Colorado, Washington, Alaska, Oregon, and Washington D.C. In 2015, two bills (HB 6473 and HB 6703) were proposed that would have made marijuana legal to possess, use, and sell for adults. Neither bill had specific information about factors such as taxes, which agency would be in charge of regulation, and how many stores would be allowed to sell marijuana. It is likely there will be further debate on these bills during the 2016 legislative session.

Adolescents and Young Adults

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  • Fergusson, DM and LJ Horwood, Does cannabis use encourage other forms of illicit drug use?Addiction, 2000. 95(4): p. 505-20. 
  • Fiellin, LE, et al., Previous use of alcohol, cigarettes, and marijuana and subsequent abuse of prescription opioids in young adults. J Adolesc Health, 2013. 52(2): p. 158- 63.
  • Lynne-Landsman, SD, CP Bradshaw, and NS Ialongo, Testing a developmental cascade model of adolescent substance use trajectories and young adult adjustment. Dev Psychopathol, 2010. 22(4): p.1681-92
  • Moss, HB, CM Chen, and HY Yi, Early adolescent patterns of alcohol, cigarettes, and marijuana polysubstance use and young adult substance use outcomes in a nationally representative sample. Drug Alcohol Depend, 2014. 136: p. 51-62.
  • Nakawaki, B and WD Crano, Predicting adolescents' persistence, non-persistence, and recent onset of nonmedical use of opioids and stimulants. Addict Behav, 2012. 37(6): p. 716-21.
  • Schepis, TS and S Krishnan-Sarin, Characterizing adolescent prescription misusers: a population-based study. J Am Acad Child Adolesc Psychiatry, 2008. 47(7): p. 745-54.
  • Swift, W, et al., Cannabis and progression to other substance use in young adults: findings from a 13-year prospective population-based study. J Epidemiol Community Health, 2012. 66(7): p. e26.
  • Arseneault, L, et al., Causal association between cannabis and psychosis: examination of the evidence.Br J Psychiatry, 2004. 184: p. 110-7.
  • Fergusson, DM, LJ Horwood, and EM Ridder, Tests of causal linkages between cannabis use and psychotic symptoms. Addiction, 2005. 100(3): p. 354-66.
  • Henquet, C, et al., Prospective cohort study of cannabis use, predisposition for psychosis, and psychotic symptoms in young people. Bmj, 2005. 330(7481): p. 11.
  • Kuepper, R, et al., Continued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study. Bmj, 2011. 342: p. d738.
  • van Os, J, et al., Cannabis use and psychosis: a longitudinal population-based study. Am J Epidemiol, 2002. 156(4): p. 319-27.
  • Zammit, S, et al., Self reported cannabis use as a risk factor for schizophrenia in Swedish conscripts of 1969: historical cohort study. Bmj, 2002. 325(7374): p. 1199. 

Neurological, Cognitive, and Mental Health Effects

  • Bolla, KI, et al., Dose-related neurocognitive effects of marijuana use. Neurology, 2002. 59(9): p. 1337-43.
  • Pope, HG, et al., Neuropsychological Performance in Long-term Cannabis Users. Archives of General Psychiatry, 2001. 58(10): p. 909-909. 
  • Rodgers, J, et al., Differential effects of Ecstasy and cannabis on self-reports of memory ability: a web-based study. Hum Psychopharmacol, 2001. 16(8): p. 619-625.
  • Roebke, PV, et al., Verbal learning in marijuana users seeking treatment: a comparison between depressed and non-depressed samples. Am J Drug Alcohol Abuse, 2014: p. 1-6. 
  • Sanchez-Torres, AM, et al., Lifetime cannabis use and cognition in patients with schizophrenia spectrum disorders and their unaffected siblings. European Archives of Psychiatry and Clinical Neuroscience, 2013. 263(8): p. 643-653.
  • Solowij, N, et al., Cognitive Functioning of Long-term Heavy Cannabis Users Seeking Treatment. JAMA, 2002. 287(9): p. 1123-1131.
  • Tamm, L., et al., Impact of ADHD and cannabis use on executive functioning in young adults. Drug Alcohol Depend, 2013. 133(2): p. 607-14.
  • Thames, AD, N Arbid, and P Sayegh, Cannabis use and neurocognitive functioning in a non-clinical sample of users. Addict Behav, 2014. 39(5): p. 994-9.
  • D'Souza, DC, et al., The psychotomimetic effects of intravenous delta-9- tetrahydrocannabinol in healthy individuals: implications for psychosis. Neuropsychopharmacology, 2004. 29(8): p. 1558-72.
  • Morrison, PD, et al., The acute effects of synthetic intravenous Delta9- tetrahydrocannabinol on psychosis, mood and cognitive functioning. Psychol Med, 2009. 39(10): p. 1607-16.
  • Morrison, PD and JM Stone, Synthetic delta-9-tetrahydrocannabinol elicits schizophrenia-like negative symptoms which are distinct from sedation. Hum Psychopharmacol, 2011. 26(1): p. 77-80.

Respiratory Effects

  • Gieringer, D, J St. Laurent, and S Goodrich, Cannabis Vaporizer Combines Efficient Delivery of THC with Effective Suppression of Pyrolytic Compounds. Journal of Cannabis Therapeutics, 2004. 4(1).
  • Lee, ML, M Novotny, and KD Bartle, Gas chromatography/mass spectrometric and nuclear magnetic resonance spectrometric studies of carcinogenic polynuclear aromatic hydrocarbons in tobacco and marijuana smoke condensates. Anal Chem, 1976. 48(2): p. 405-16.
  • Moir, D, et al., A comparison of mainstream and sidestream marijuana and tobacco cigarette smoke produced under two machine smoking conditions. Chem Res Toxicol, 2008. 21(2): p. 494-502.
  • Sparacino, CM, PA Hyldburg, and TJ Hughes, Chemical and Biological Analysis of Marijuana Smoke Condensate, U.S.D.o.H.a.H. Services, Editor. 1990. 
  • Tashkin, DP, BJ Shapiro, and IM Frank, Acute effects of smoked marijuana and oral delta9-tetrahydrocannabinol on specific airway conductance in asthmatic subjects. Am Rev Respir Dis, 1974. 109(4): p. 420-8.
  • Tashkin, DP, BJ Shapiro, and IM Frank, Acute pulmonary physiologic effects of smoked marijuana and oral 9 -tetrahydrocannabinol in healthy young men. N Engl J Med, 1973. 289(7): p. 336-41.
  • Tashkin, DP, et al., Effects of smoked marijuana in experimentally induced asthma. Am Rev Respir Dis, 1975. 112(3): p. 377-86.
  • Aldington, S, et al., Effects of cannabis on pulmonary structure, function and symptoms. Thorax, 2007. 62(12): p. 1058-63.
  • Bloom, JW, et al., Respiratory effects of non-tobacco cigarettes. Br Med J (Clin Res Ed), 1987. 295(6612): p. 1516-8.
  • Moore, BA, et al., Respiratory effects of marijuana and tobacco use in a U.S. sample. J Gen Intern Med, 2005. 20(1): p. 33-7.
  • Roth, MD, et al., Airway inflammation in young marijuana and tobacco smokers. Am J Respir Crit Care Med, 1998. 157(3 Pt 1): p. 928-37.
  • Sherrill, DL, et al., Respiratory effects of non-tobacco cigarettes: a longitudinal study in general population. Int J Epidemiol, 1991. 20(1): p. 132-7.
  • Tashkin, DP, et al., Respiratory symptoms and lung function in habitual heavy smokers of marijuana alone, smokers of marijuana and tobacco, smokers of tobacco alone, and nonsmokers. Am Rev Respir Dis, 1987. 135(1): p. 209-16.
  • Taylor, DR, et al., The respiratory effects of cannabis dependence in young adults. Addiction, 2000. 95(11): p. 1669-77.
  • Barsky, SH, et al., Histopathologic and molecular alterations in bronchial epithelium in habitual smokers of marijuana, cocaine, and/or tobacco. J Natl Cancer Inst, 1998. 90(16): p. 1198-205.
  • Fligiel, SE, et al., Tracheobronchial histopathology in habitual smokers of cocaine, marijuana, and/or tobacco. Chest, 1997. 112(2): p. 319-26.
  • Gong, H, Jr., et al., Tracheobronchial changes in habitual, heavy smokers of marijuana with and without tobacco. Am Rev Respir Dis, 1987. 136(1): p. 142-9.

Automobile Accidents

  • Asbridge, M, JA Hayden, and JL Cartwright, Acute cannabis consumption and motor vehicle collision risk: systematic review of observational studies and metaanalysis. BMJ (Clinical research ed.), 2012. 344(February): p. e536-e536.
  • Hartman, RL and MA Huestis, Cannabis effects on driving skills. Clinical chemistry, 2013. 59(3): p. 478-92.   
  • Lowenstein, SR and J Koziol-McLain, Drugs and Traffic Crash Responsibility: A Study of Injured Motorists in Colorado. The Journal of Trauma: Injury, Infection, and Critical Care, 2001. 50(2): p. 313-320.
  • Drummer, OH, et al., The involvement of drugs in drivers of motor vehicles killed in Australian road traffic crashes. Accident Analysis & Prevention, 2004. 36(2): p. 239- 248.
  • Laumon, B, et al., Cannabis intoxication and fatal road crashes in France: population based case-control study. BMJ, 2005. 331(7529): p. 1371.
  • Drummer, OH, et al., The involvement of drugs in drivers of motor vehicles killed in Australian road traffic crashes. Accident Analysis & Prevention, 2004. 36(2): p. 239- 248.
  • Laumon, B, et al., Cannabis intoxication and fatal road crashes in France: population based case-control study. BMJ, 2005. 331(7529): p. 1371.
  • Mura, P, et al., Comparison of the prevalence of alcohol, cannabis and other drugs between 900 injured drivers and 900 control subjects: results of a French collaborative study. Forensic Science International, 2003. 133(1-2): p. 79-85.

Dose and Drug Interactions

  • Cone, EJ and RE Johnson, Contact highs and urinary cannabinoid excretion after passive exposure to marijuana smoke. Clin Pharmacol Ther, 1986. 40(3): p. 247-56. 
  • Cone, EJ, et al., Non-Smoker Exposure to Secondhand Cannabis Smoke. I. Urine Screening and Confirmation Results. J Anal Toxicol, 2014.
  • Cone, EJ, et al., Passive inhalation of marijuana smoke: urinalysis and room air levels of delta-9-tetrahydrocannabinol. J Anal Toxicol, 1987. 11(3): p. 89-96.
  • Law, B, et al., Passive inhalation of cannabis smoke. J Pharm Pharmacol, 1984. 36(9): p. 578-81.
  • Mason, AP, et al., Cannabinoids in plasma after passive inhalation of marijuana smoke. Jama, 1983. 249(4): p. 475-6.
  • Morland, J, et al., Cannabinoids in blood and urine after passive inhalation of Cannabis smoke. J Forensic Sci, 1985. 30(4): p. 997-1002.
  • Mule, SJ, P Lomax, and SJ Gross, Active and realistic passive marijuana exposure tested by three immunoassays and GC/MS in urine. J Anal Toxicol, 1988. 12(3): p. 113-6.
  • Niedbala, S, et al., Passive cannabis smoke exposure and oral fluid testing. J Anal Toxicol, 2004. 28(7): p. 546-52.
  • Niedbala, RS, et al., Passive cannabis smoke exposure and oral fluid testing. II. Two studies of extreme cannabis smoke exposure in a motor vehicle. J Anal Toxicol, 2005. 29(7): p. 607-15.
  • Norchem Lab. Urine Drug Test Information Sheet: Marijuana. 8/8/2014]; Available from:
  • Perez-Reyes, M, S di Guiseppi, and KH Davis, Passive inhalation of marijuana smoke and urinary excretion cannabinoids. Jama, 1983. 249(4): p. 475.
  • Rohrich, J, et al., Concentrations of delta9-tetrahydrocannabinol and 11-nor-9- carboxytetrahydrocannabinol in blood and urine after passive exposure to Cannabis smoke in a coffee shop. J Anal Toxicol, 2010. 34(4): p. 196-203.
  • Berghaus, G, N Scheer, and P Schmidt. Effects of cannabis on psychomotor skills and driving performance - a metaanalysis of experimental studies. 1995 8/31/2014]; Available from:
  • Berghaus, G, G Sticht, and W Grellner, Meta-analysis of empirical studies concerning the effects of medicines and illegal drugs including pharmacokinetics on safe driving, in Driving under the influence of drugs, alcohol, and medicines (DRUID) 6th framework programme. 2011, Center for Traffic Sciences at the University of Wurzburg. p. Cannabis section pgs 168-176.
  • Bosker, WM, et al., Medicinal Delta(9) -tetrahydrocannabinol (dronabinol) impairs on-the-road driving performance of occasional and heavy cannabis users but is not detected in Standard Field Sobriety Tests. Addiction, 2012. 107(10): p. 1837-44.
  • Curran, HV, et al., Cognitive and subjective dose-response effects of acute oral Delta 9-tetrahydrocannabinol (THC) in infrequent cannabis users. Psychopharmacology (Berl), 2002. 164(1): p. 61-70.
  • Grotenhermen, F, et al., Developing limits for driving under cannabis. Addiction, 2007. 102(12): p. 1910-7.
  • Hartman, RL and MA Huestis, Cannabis effects on driving skills. Clin Chem, 2013. 59(3): p. 478-92.
  • Huestis, MA, et al., Characterization of the absorption phase of marijuana smoking. Clin Pharmacol Ther, 1992. 52(1): p. 31-41.
  • Lile, J.A., et al., Pharmacokinetic and pharmacodynamic profile of supratherapeutic oral doses of Delta(9) -THC in cannabis users. J Clin Pharmacol, 2013. 53(7): p. 680- 90.
  • Menetrey, A, et al., Assessment of driving capability through the use of clinical and psychomotor tests in relation to blood cannabinoids levels following oral administration of 20 mg dronabinol or of a cannabis decoction made with 20 or 60 mg Delta9-THC. J Anal Toxicol, 2005. 29(5): p. 327-38.
  • Ramaekers, JG, et al., Cognition and motor control as a function of Delta9-THC concentration in serum and oral fluid: limits of impairment. Drug Alcohol Depend, 2006. 85(2): p. 114-22.
  • Reeve, VC, et al., Plasma concentrations of delta-9-tetrahydrocannabinol and impaired motor function.Drug Alcohol Depend, 1983. 11(2): p. 167-75.