Researchers from Texas A&M University and the University of Florida, Gainesville evaluated drug use patterns from a nationally representative sample of 2,835 12th graders.
Authors found that youth use of alcohol most often preceded the use of tobacco or marijuana. They also reported subjects’ age of alcohol initiation is the strongest predictor of later polydrug use.
“Alcohol is the most commonly used substance, and the majority of polysubstance using respondents consumed alcohol prior to tobacco or marijuana initiation,” they reported. “Respondents initiating alcohol use in sixth grade reported significantly greater lifetime illicit substance use and more frequent illicit substance use than those initiating alcohol use in ninth grade or later.”
They concluded, “Our results … assert that the earlier one initiates alcohol use, the more likely that they will engage in future illicit substance use.”
The findings are inconsistent with recent claims made by several prominent lawmakers that cannabis is a ‘gateway’ to later substance abuse.
Studies conducted by the RAND Corporation and others have previously dismissed any alleged causal role of marijuana as a gateway to subsequent illicit drug abuse, finding, “There is no conclusive evidence that the drug effects of marijuana are causally linked to the subsequent abuse of other drugs.”
An abstract of the study, “Prioritizing Alcohol Prevention: Establishing Alcohol as the Gateway Drug and Linking Age of First Drink With Illicit Drug Use,” appears online here.
Marijuana use by adolescents is not associated with lower IQ or poorer educational performance once adjustments are made for potential confounders, specifically cigarette smoking, according to longitudinal data published online ahead of print in the Journal of Psychopharmacology.
British investigators assessed the relationship between cumulative cannabis use and IQ at the age of 15 and educational performance at the age of 16 in a cohort of 2,235 adolescents.
After researchers adjusted for potentially confounding variables, such as childhood depression and cigarette use, they reported, “[T]hose who had used cannabis [greater than or equal to] 50 times did not differ from never-users on either IQ or educational performance.”
By contrast, teen cigarette smoking was associated with poorer educational outcomes even after researchers adjusted for other confounding variables.
Researchers concluded, “In summary, the notion that cannabis use itself is causally related to lower IQ and poorer educational performance was not supported in this large teenage sample.”
A widely publicized New Zealand study published in 2012 in The Proceedings of the National Academy of Sciences reported that frequent use of cannabis by those under the age of 18 was associated with lower IQ by age 38. However, a separate review of the data published later in the same journal suggested that the changes were likely the result of socioeconomic differences, not cannabis use.
More recently, the results of a 2015 study in the journal Drug and Alcohol Dependence reported that the effects of persistent adolescent cannabis use on academic performance “became non-significant after controlling for persistent alcohol and tobacco use.”
Full text of the study, “Are IQ and educational outcomes in teenagers related to their cannabis use? A prospective cohort study,” appears online here.
Cannabis use is inversely associated with incidences of bladder cancer in males, according epidemiological findings published in the February issue of the journal Urology.
Investigators at the Kaiser Permanente Los Angeles Medical Center, Department of Neurology assessed the association of cannabis use and tobacco smoking on the risk of bladder cancer in a multiethnic cohort of more than 80,000 men aged 45 to 69 years old over an 11-year period.
Researchers determined that a history of cannabis use was associated with a decreased risk of bladder cancer. By contrast, tobacco use was associated with an increased risk of cancer.
“After adjusting for age, race or ethnicity, and body mass index, using tobacco only was associated with an increased risk of bladder cancer (hazard regression 1.52) whereas cannabis use was only associated with a 45 percent reduction in bladder cancer incidence (HR 0.55),” investigators reported.
Subjects who reported using both tobacco and cannabis possessed a decreased risk of cancer (HR 1.28) compared to those subjects who used tobacco only (HR 1.52).
The study is the first to indicate that cannabis use may be inversely associated with bladder cancer risk.
“In this multiethnic cohort of 82,050 men, we found that cannabis use alone was associated with a decreased risk of bladder cancer. … [M]en who used tobacco alone were 1.5 times more likely to develop bladder cancer when compared with men who did not use tobacco or cannabis. … However, among men who used both substances, this risk of bladder cancer was mitigated. … If this represents a cause and effect relationship, this pathway may provide new opportunities for the prevention and/or treatment of bladder cancer.”
In 2009, Brown University researchers similarly reported that the moderate long-term use of marijuana was associated with a reduced risk of head and neck cancers in a multi-center cohort involving over 1,000 subjects. Investigators further reported that marijuana use “modified the interaction between alcohol and cigarette smoking, resulting in a decreased HNSCC (head and neck squamous cell carcinoma) risk among moderate smokers and light drinkers, and attenuated risk among the heaviest smokers and drinkers.”
Read the abstract of the study, “Association between cannabis use and the risk of bladder cancer: Results from the California Men’s Health Survey,” online here.
The inhalation of one marijuana cigarette per day over a 20-year period is not associated with adverse changes in lung health, according to data published online ahead of print in the journal Annals of the American Thoracic Society.
Investigators at Emory University in Atlanta assessed marijuana smoke exposure and lung health in a large representative sample of US adults age 18 to 59. Researchers reported that cannabis exposure was not associated with FEV1 (forced expiratory volume) decline or deleterious change in spirometric values of small airways disease.
Authors further reported that marijuana smoke exposure may even be associated with some protective lung effects among long-term smokers of tobacco. Investigators acknowledged, “[T]he pattern of marijuana’s effects seems to be distinctly different when compared to that of tobacco use.”
Researchers also acknowledged that habitual cannabis consumers were more likely to self-report increased symptoms of bronchitis, a finding that is consistent with previous literature. Separate studies indicate that subjects who vaporize cannabis report fewer adverse respiratory symptoms than do those who inhale combustive marijuana smoke.
Authors concluded, “[I]n a large representative sample of US adults, ongoing use of marijuana is associated with increased respiratory symptoms of bronchitis without a significant functional abnormality in spirometry, and cumulative marijuana use under 20 joint-years is not associated with significant effects on lung function.”
This study is the largest cross-sectional analysis to date examining the relationship between marijuana use and spirometric parameters of lung health.
A separate study published in 2012 in The Journal of the American Medical Association (JAMA) similarly reported that cumulative marijuana smoke exposure over a period of up to 7 joint-years (the equivalent of up to one marijuana cigarette per day for seven years) was not associated with adverse effects on pulmonary function.
A 2013 review also published in the Annals of the American Thoracic Society acknowledged that marijuana smoke exposure was not positively associated with the development of lung cancer, chronic obstructive pulmonary disease (COPD), emphysema, or bullous lung disease. It concluded: “[H]abitual use of marijuana alone does not appear to lead to significant abnormalities in lung function. Findings from a limited number of well-designed epidemiological studies do not suggest an increased risk of either lung or upper airway cancer from light or moderate use. … Overall, the risks of pulmonary complications of regular use of marijuana appear to be relatively small and far lower than those of tobacco smoking.”
You may view an abstract of the study, “Effects of marijuana exposure on expiratory airflow: A study of adults who participated in the US National Health and Nutrition Examination Study,” here.
Among those voters age 18 to 40, 47 percent ranked alcohol as the most harmful substance to society, well ahead of both tobacco (27 percent) and cannabis (13 percent). (Thirteen percent of respondents were undecided.) Respondents among all age and ethnic groups were consistent in ranking marijuana as the least harmful of the three substances, as were self-identified Democrats and Independents. (Republicans rated tobacco to be the most harmful of the three products.)
“[These] numbers suggest younger Americans are upending societal conventions, which have long seen alcohol as an acceptable drug while condemning marijuana,” stated Rare.us in an accompanying press release.
The results are somewhat similar to those of a Wall Street Journal/NBC News poll released in March which reported that most Americans believe tobacco to be most harmful to health (49 percent), followed by alcohol (24 percent), sugar (15 percent), and marijuana (8 percent).
Under federal law, marijuana is classified as a schedule I controlled substance, meaning that its alleged harms are equal to those of heroin. Both tobacco and alcohol are unscheduled under federal law.
According to a study published in 2004 in the Journal of the American Medical Association, the leading causes of death in the United States ware tobacco (435,000 deaths; 18.1 percent of total US deaths), poor diet and physical inactivity (365,000 deaths; 15.2 percent), and alcohol consumption (85,000 deaths; 3.5 percent).