Cannabis consumption has multiple and significant CNS effects. Of note, a tolerance to many of these behavioral and somatic effects may develop (2). We will delineate the different CNS functions affected.
Psychological: The acute effects of smoking or inhaling vaporized cannabis typically include an onset of euphoria and relaxation within 90 seconds. The maximum euphoria is typically experienced approximately 15-30 minutes after inhalation. The euphoria or “high” often plateaus and can last for several hours. Although most people experience euphoria after inhaling cannabis, some patients actually experience an anxiety attack or a psychotic event (1). The patients that experience an anxiety attack are usually the cannabis-naïve patients. THC is the cannabinoid that is responsible for a majority of the psychoactive effects of cannabis. CBD does not have psychoactive effects but it may modulate the psychoactive effects of THC (3).
Cannabis is a CNS depressant and may cause drowsiness or somnolence. It can improve the quality of sleep for some people. Its CNS depressant effects are additive with other CNS depressants, including opioids (1).
Individuals who consume cannabis products orally or oromucosally may also experience euphoria, relaxation, anxiety, paranoia, drowsiness and/or somnolence, but the timing is delayed and the intensity of these sensations is typically less than after inhaling cannabis products.
According to a study by Karshner et al., CBD does not decrease the relaxing effect significantly, but may attenuate the “high” feeling effect one gets after consuming THC (4). The monograph of nabilone (a synthetic form of THC taken orally) states that the adverse psychotropic reactions can persist for 48 to 72 hours following cessation of treatment (5).
When writing about cannabis intoxication, Weinstein et al. state, “The most severe effects (anxiety, panic, psychosis) are best treated symptomatically with a benzodiazepine or second-generation (atypical) anti-psychotic medication. No medication is approved specifically for treatment of cannabis intoxication (6).”
Cognitive and psychomotor function: Scientific reviews indicate that smoking cannabis is associated with an acute impairment of cognitive function and a decreased ability to perform tasks requiring short-term memory. Reasoning becomes impaired and thoughts can become non-cohesive. Also, the ability to perform activities requiring concentration and/or complex motor skills can be significantly impaired (1, 2). According to a cross sectional study by Honarmand et al., prolonged use of ingested or inhaled cannabis in multiple sclerosis patients was associated with a poorer performance in multiple cognitive areas, including working memory, executive functions and speed of information processing (7). Oral and oromucosal ingestion of cannabinoid medications such as dronabinol and nabilone (synthetic versions of delta -9-THC) and nabiximols (Sativex) have been associated with decreased psychomotor performance. In the drug monographs of these cannabis products, patients are warned not to drive or operate complex machinery after consuming the medication (5, 8, 9).
Perception and sensory: Some of the acute effects of cannabis inhalation include hallucinations, time distortion, and an intensification of sensory experiences. Tactile, auditory, visual and taste processing can all be affected (1, 2). Oral ingestion of cannabis products is also associated with visual-spatial perception distortion (7), blurred vision and rarely hallucinations (5).
Whether inhaled or consumed orally or oromucosally, cannabis does have analgesic properties. Its analgesic effects are similar to that of codeine’s analgesic effects (1), but its mechanism of action is different.
Motor Function: Initially, the inhalation of cannabis may cause an increase in motor activity. This increase in activity is followed by a decrease in overall motor activity. Coordination is negatively impacted. Ataxia, dysarthria and overall weakness are not uncommon (1). Of note, in patients with some movement disorders such as Tourette’s, cannabis may have therapeutic effects (2). According to the drug monographs of nabilone and dronabinol, some individuals who have taken these synthetic THC medicines have experienced tremors, ataxia, and rarely seizures (5, 8).
Note: According to the drug monographs of cannabinoid medications, elderly patients may be more sensitive to the psychoactive and neurologic side effects of cannabinoids (5, 8, 9).
Appetite (along with food intake and energy metabolism): Cannabis stimulates appetite (1). Studies have shown that there is a high concentration of cannabinoid CB1 receptors in the areas of the brain that control food intake and satiety, and these findings suggest that there is an association between cannabis consumption and appetite regulation (10, 11, 12). Additionally, studies suggest that the endocannabinoid system modulates taste sensation as well as the metabolism of lipids and glucose (11 - 14). Therefore, cannabis may have clinical use in the palliative care for anorexia due to opioids, antiviral drugs, AIDS related illnesses and/or cancer (15).
Of note, “according to available studies, appetite stimulation as well as weight gain may occur (due to cannabis use) in patients with physical debilitation due to HIV/AIDS and/or cancer. However, while weight gain may occur, it is not greater than currently available agents for inducing weight gain (e.g. megestrol, a man-made version of the human hormone progesterone)(16)."
Nausea: Cannabis has anti-emetic properties (1). “Treatment of the nausea and vomiting associated with chemotherapy was one of the first medical uses of THC and other cannabinoids. THC is an effective antiemetic agent in patients undergoing chemotherapy, but patients often state that marijuana is more effective in suppressing nausea. Other, unidentified compounds in marijuana may enhance the effect of THC (as appears to be the case with THC and cannabidiol, which operate through different antiemetic mechanisms) (17)."