The state of Colorado has compiled a comprehensive, 188-page report that summarizes most of the medical findings to date related to consuming cannabis. Looking at nearly every aspect of its effects, the report left almost no stone unturned regarding the effect of marijuana of public health. Along with the many findings published, research gaps and biases were pointed out as well.
In the majority of cases, research findings couldn’t prove causality; but, rather, only association. Though marijuana use may have been found to be associated with certain adverse effects, researchers weren’t able to prove marijuana caused the adverse effects. In addition, because marijuana was completely illegal before 1996, “research funding, when appropriated, was commonly sought to identify adverse effects from marijuana use. This legal fact introduces both funding bias and publication bias into the body of literature related to marijuana use.”
The study attempted to take this into account and identified knowledge gaps where further research was necessary, but it can’t be denied that the majority of research funded for cannabis had been aimed at showing negative effects for political reasons.
Exposure During Pregnancy, with Children and Adolescents
The study found moderate evidence that marijuana use during pregnancy was associated with decreased academic ability, cognitive function and attention in the offspring. Those effects may not appear until adolescence. They also found moderate evidence that exposure during pregnancy was associated with decreased growth. The committee found moderate evidence that states with increased legal access to cannabis lead to more unintentional exposure to children of significant clinical importance, but child-resistant packaging helps reduce exposure.
Researchers also found substantial evidence that cannabis use in adolescents and young adults was associated with future addictions, and an increased risk in developing psychotic disorders. This in no way proves the “gateway” effect, because future addictions can’t be pinned on cannabis use. There was also a moderate association between cannabis use and short-term impairment of cognitive and academic abilities, and users were less likely to graduate high school.
Consuming 10 mg of THC or more impaired a person’s ability to drive. They found waiting at least six hours after smoking cannabis with an equivalent of 35 mg of THC was enough for impairment to go away in occasional users. A person had to wait longer if they consumed it orally. An occasional user had to wait eight hours for impairment to go away after consuming 18 mg of THC.
Regarding edibles, it can take up to four hours or sometimes longer for peak effects to kick in. Consuming alcohol and cannabis likely caused more impairment then using just one alone. They also found second-hand cannabis smoke was unlikely to make a person fail a drug test.
Neurological, Cognitive and Mental Health
They “found substantial evidence for associations between marijuana use and memory impairments lasting at least seven days after last use, as well as the potential for acute psychotic symptoms immediately after use,” and also “moderate evidence that adults who use marijuana regularly are more likely than non-users to have symptoms or diagnosis of depression.” Once again, these are only associations, not proof that cannabis caused any of these effects.
They “found substantial evidence that marijuana smoke contains many of the same carcinogens found in tobacco smoke.” Acute use (within the past hour), was associated with short-term improvements in lung airflow, something they found for both smoked and edible cannabis products. However, they “found moderate evidence that heavy marijuana smoking is associated with mild airflow obstruction.” They “found substantial evidence that heavy marijuana smoking is associated with pre-malignant lesions in the airway, but mixed evidence for whether or not marijuana smoking is associated with lung cancer.”
Effects Beyond the Lungs
“There were relatively few literature reports of marijuana use related to myocardial infarction (heart attacks), ischemic stroke, male infertility, testicular cancer, prostate cancer and bladder cancer.” Limited evidence suggested an increased risk for heart attack, stroke, testicular cancer, prostate cancer but mixed evidence over whether it there was an increased risk in male infertility.
Cannabis Use and Injury
“The committee found substantial evidence that risk of motor vehicle crash doubles among drivers with recent marijuana use.” Also, the more you consumed, the higher risk of crash you had. “The evidence is limited, but data suggest that the risk of non-traffic workplace injuries may be higher with marijuana use.”
This may all sound damning, but nothing was entirely conclusive except for the fact that more information needs to be gathered. Besides the lack of causality relating cannabis to negative health effects, most associations found were loose at best.