What do we really know about the short-term impact of recreational cannabis use? A WHO report summarized the available scientific evidence.
Earlier this year, the World Health Organization published a report titled “The health and social effects of non-medical cannabis use”—the first in the last twenty years. The extensive research did not consider the toxicology, pharmacology, or possible medicinal applications of marijuana but focused on the recreational use of the plant, from its impact on brain development to its effects on physical health.
In 1970, cannabis was classified as a Schedule I substance not because of sound science but because of its absence. Fortunately, today, only a small minority of people doubt the medical benefits of this “dangerous, illicit drug,” given the number of medical marijuana studies. But what about the health consequences of the non-medical use of the substance?
As a psychoactive substance, marijuana has various cognitive effects, most of which fade withing a few hours after consumption.
In 2011, scientists of The Scripps Research Institute of California published a broad study of the impact of cannabis use on cognitive functions. They reviewed of the effect the plant has on an array of cognitive functions, including attention, decision-making, risk-taking, concentration, reaction time, and working memory.
The results of most studies have been quite disappointing: depending on the dose and frequency of consumption, cannabis has been shown to reduce (in varying degrees) motor coordination, ability to organize and plan, make decisions, and solve problems.
According to the studies, cannabis has the most robust effect on short-term episodic and working memory.
Studies also found that people under influence of marijuana show much worse results in math and often have some problems with verbal expression. Some studies also report that cannabis users under influence become more impulsive and take more risks compared to non-users.
Most of the cognitive impairments last for up to 24 hours. The drug “interferes with driving skills and increases the risk of injuries.” Short-term effects of marijuana intoxication have been suggested to have a negative influence on driving ability.
According to the WHO report, THC, the main psychoactive component of cannabis, can make a minority of first-time cannabis users anxious, cause paranoia, and even trigger hallucinations.
However, the possible side-effects are highly individualized based on various factors, including frequency of use, dose and potency of the substance consumed, and the way of consumption. For instance, the outcome of oral ingestion of potent cannabis product may be unpredictable even for experienced users. Some inexperienced cannabis users are more prone to becoming anxious, vomiting, or experiencing hallucinations, or panic attacks. A recent study showed that hallucinations may occur at low doses in individuals predisposed to psychosis, schizophrenia, or other psychotic disorders.
Acute exposure to marijuana increases blood pressure and heart rate. Researchers report that, in some cases, cannabis can cause orthostatic hypotension and serious cardiovascular complications, such as acute coronary syndrome and strokes. Furthermore, according to researchers, the risk of experiencing myocardial infarction after smoking cannabis for patients with a recent heart attack increases four times compared to cannabis users with no history of myocardial infarction. The risk quickly decreases with time.
Unlike tobacco smoking that causes acute bronchial constriction, cannabis smoking may produce acute dilation in proportion to the dose of THC. Cannabis smokers that prefer to combine marijuana and tobacco are at risk of suffering from different acute bronchial effects.