Mechanism of Action and General Health Changes

The dried leaves, stems or flowers of the Cannabis Sativa hemp plant are used to produce marijuana. The sticky resin from the plant can be concentrated to produce hashish or hash oil. The concentrations of THC differ in each component: 7-12% in the leaves, 2-8% in hashish and 15-20% in the hash oil. The most common way of using cannabis is through smoking, similarly to smoking a cigarette (hand rolled), in a pipe or water pipe (bong) or through ingestion in food. Other chemicals are found in marijuana: cannabidiol, cannabinol and Β-caryophyllene, which adversely affect health.12

THC effects are immediate, with absorption directly to the bloodstream via the lungs if smoked, and carried to other organs and the brain. The psychoactive effects occur within the endocannabinoid system, affecting parts of the brain and cognitive impairment. Certain areas in the brain, such as the hippocampus, the cerebellum, the basal ganglia and the cerebral cortex, have a higher concentration of cannabinoid receptors. These receptors influence sensory and time perception, coordinated movement, thinking, concentration and memory. Several studies document the loss of short-term memory and other reports detail a compromise of longer-term memory based on the amount and duration of use. One study related a loss of 8 points in IQ tests between the ages of 13 and 38 with those individuals who smoked heavily, beginning in their teen years. These cognitive abilities are unable to be restored in adulthood.13

Other health effects of marijuana include an increase in respiratory rate, heart rate, and blood pressure, with this effect lasting more than three hours. The risk of a heart attack increases by up to 4.8 fold in the first hour after smoking marijuana. This risk is greater in those with risk factors such as high blood pressure, arrhythmias or other cardiac diseases. Changes within the lungs from smoking marijuana involve enlargement of the bronchial passages after relaxation of the blood vessels. In addition, engorgement of the blood vessels in the eyes causes a reddened appearance. The hydrocarbons found in marijuana smoke are 50-70% more carcinogenic than tobacco smoke and an irritant to the lungs. Respiratory conditions common in tobacco smokers such as daily cough, phlegm production and risk of lung infections are also found in marijuana smokers. There are currently no studies that confirm the risk for lung cancer with marijuana smoke.13

Links to mental illnesses with marijuana use have been observed with suicidal thoughts among adolescents, depression, anxiety and an increase risk of developing schizophrenia or other psychoses. The impairment to judgment with marijuana use allows for the contribution to the risk of injury, particularly in motor vehicle accidents. A study from Columbia's Mailman School of Public Health collected data from toxicology reports on drivers of over 20,000 fatal automobile accidents and found that marijuana was involved in 12% of those crashes.14 Addiction to marijuana is possible, contrary to common beliefs, with 9% of users becoming addicted to marijuana, particularly with those who start in their teens with 25-50% who use marijuana daily.12