Cannabis-influenced driving performance is significantly different from alcohol-induced driving behavior, according to driving simulator data published in the Journal of Applied Toxicology.
Investigators with the National Institute on Drug Abuse and the University of Iowa evaluated simulated driving performance in subjects following their consumption of vaporized cannabis, alcohol, or placebo.
Researchers reported that cannabis administration was associated compensatory driving behavior, such as decreased mean speed and increased mean following distance, whereas alcohol administration was associated with faster driving. Their findings are similar to those of other driving studies, like those here and here.
Investigators also reported that cannabis dosing in combination with low quantities of alcohol “mitigated drivers’ tendency to drive faster with alcohol” – a finding that contrasts with prior data acknowledging that the two substances combined typically possess an additive adverse effect on psychomotor performance.
“THC concentration-dependent associations with decreased speed, increased time below the speed limit and increased following distance suggest possible awareness by drivers of potential impairment and attempts to compensate,” authors concluded. “The compensatory behavior exhibited by cannabis-influenced drivers distinctly contrasts with an alcohol-induced higher risk behavior, evidenced by greater percent speed.”
According to the findings of a recently published literature review of crash culpability studies, “[A]cute cannabis intoxication is related to a statistically significant risk increase of low to moderate magnitude [odds ratio between 1.2 and 1.4].” By contrast, a 2015 case-control study by the US National Highway Traffic Safety Administration reported that driving with legal amounts of booze in one’s system is associated with a nearly four-fold increased crash risk (odds ratio = 3.93).
An abstract of the study, “Cannabis effects on driving longitudinal control with and without alcohol,” appears online here.
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 consumers do not typically use cannabis and alcohol in combination with one another, regardless of whether they are consuming cannabis for medicinal or social purposes, according to data published online ahead of print in the journal Addiction.
Investigators with the RAND Drug Policy Research Center and the University of California, Irvine surveyed marijuana use patterns among participants between the ages of 18 and 91 in four states: Colorado, New Mexico, Oregon, and Washington. (The use of marijuana for medicinal purposes is legal in New Mexico, while laws in Colorado, Oregon, and Washington permit adults to possess and purchase cannabis for both medicinal and/or recreational purposes.)
Authors reported, ”Individuals who use cannabis do not commonly use it with alcohol, irrespective of whether they are consuming cannabis recreationally or medically.” They concluded, “Fewer than one in five recreational users report simultaneous use of alcohol and cannabis most or all of the time and less than three percent of medicinal users report frequent simultaneous use of alcohol and cannabis.”
An abstract of the study, “A baseline view of cannabis use among legalizing states and their neighbors,” appears online here.
Investigators from the University of Victoria in British Columbia assessed the influence of medical marijuana access on other drug-taking behaviors in a cohort of 473 Canadian adults licensed to engage in cannabis therapy.
“Substituting cannabis for one or more of alcohol, illicit drugs or prescription drugs was reported by 87 percent of respondents, with 80.3 percent reporting substitution for prescription drugs, 51.7 percent for alcohol, and 32.6 percent for illicit substances,” they reported.
Rates of substitution were highest among respondents between the ages of 18 and 40. Patients using cannabis for pain were most likely to use pot as a substitute for prescription drugs.
Authors concluded, “The finding that cannabis was substituted for alcohol and illicit substances suggests that the medical use of cannabis may play a harm reduction role in the context of use of these substances, and could have implications for substance use treatment approaches requiring abstinence from cannabis in the process of reducing the use of other substances.”
Evaluations of patients enrolled in state-specific medical marijuana programs, including those in Arizona, California, and Rhode Island, yield similar results — finding that patients are particularly likely substitute cannabis for opioids. According to a recently published National Bureau of Economic Research report, states that permit qualified patients to access medical marijuana via dispensaries possess lower rates of opioid addiction and overdose deaths as compared to states that do not.
An abstract of the study, “Substituting cannabis for prescription drugs, alcohol and other substances among medical cannabis patients: The impact of contextual factors,” appears online here.
It was less than a year ago when the mainstream media was chock-full of headlines like this one: ‘Brain changes associated with casual marijuana use in young adults, study finds.’ The alarmist headlines were in response to a controversial paper published by researchers at Harvard University in Boston and Northwestern University in Chicago which alleged to have found differences in brain morphology in a cohort of 20 college-age marijuana users as compared to 20 non-users. The study’s investigators attributed the differences to subjects’ cannabis use.
But a funny thing happened when a team of scientists from the University of Colorado and the University of Kentucky tried to replicate these results in a separate, larger sample (158 participants) of subjects after rigorously controlling for both groups’ use of alcohol.
Writing in the January 28 edition of The Journal of Neuroscience, authors summarized:
“[T]his retrospective study examined brain morphology in a sample of adult daily marijuana users (n = 29) versus nonusers (n = 29) and a sample of adolescent daily users (n = 50) versus nonusers (n = 50). Groups were matched on a critical confounding variable, alcohol use, to a far greater degree than in previously published studies.
We acquired high-resolution MRI scans, and investigated group differences in gray matter using voxel-based morphometry, surface-based morphometry, and shape analysis in structures suggested to be associated with marijuana use, as follows: the nucleus accumbens, amygdala, hippocampus, and cerebellum.
No statistically significant differences were found between daily users and nonusers on volume or shape in the regions of interest. Effect sizes suggest that the failure to find differences was not due to a lack of statistical power, but rather was due to the lack of even a modest effect.”
Why the contradictory results? Investigators speculated that previously reported imaging studies failed to adequately control for the impact of alcohol, a substance that “unlike marijuana, … has been unequivocally associated with deleterious effects on brain morphology and cognition in both adults and adolescents.” In other words, researchers theorized that previously reported differences in the brain images of marijuana consumers as compared to non-users were likely because of subjects consumption of booze, not cannabis.
They concluded, “In sum, the results indicate that, when carefully controlling for alcohol use, gender, age, and other variables, there is no association between marijuana use and standard volumetric or shape measurements of subcortical structures. … [I]t seems unlikely that marijuana use has the same level of long-term deleterious effects on brain morphology as other drugs like alcohol. The press may not cite studies that do not find sensational effects, but these studies are still extremely important.”
An abstract of the study, “Daily Marijuana Use Is Not Associated with Brain Morphometric Measures in Adolescents or Adults,” is online here.