Outside of Canada and the Netherlands, there is no inherent difference between herbal cannabis used recreationally and that used medically. For that reason, medical cannabis may be best understood as the use of cannabis under ongoing medical supervision, with an established diagnosis of the target symptom-disease complex. Herbal cannabis is used in conjunction with, or in consideration of, other pharmacological and nonpharmacological approaches and with the goal of reaching prespecified treatment outcomes.
Medical cannabis is most frequently administered either by smoking or vaporization or in the form of edible preparations. None of these approaches has been standardized, however, and the effectiveness of edible cannabis preparations has not been evaluated in clinical trials. Smoked cannabis has been evaluated in a small number of randomized controlled trials involving patients suffering from neuropathic pain conditions.
In each of the trials, patients experienced a reduction in pain intensity at THC concentrations of 3.9 percent or higher. A zero percent THC dose was used as the placebo condition; this formulation was created with cannabis from which all cannabinoid substances had been removed by alcohol extraction. Adverse events from these studies were mild to moderate and included drowsiness, dizziness, and dry mouth.
No serious or severe adverse events were reported.
A major safety concern associated with medical cannabis is the possibility of medical use encouraging or transitioning into recreational use, which is associated with side effects that range from acute to chronic. Acute effects include intoxication, impaired cognition and motor function, elevated heart rate, anxiety, and psychosis in predisposed individuals. Chronic effects include bronchitis (from smoked cannabis), psychological cannabis dependency, loss of motivation, and cognitive deficits. By and large these effects seem to disappear on abstinence.