There are many life threatening, as well as psychological, dangers due to the use of marijuana. Life threatening dangers include lung cancer, trouble breathing, a weakened immune system, asthma, poor driving ability, increased heart rate, high blood pressure, and reproduction problems. Effects marijuana has on the brain include poor short term memory, a short attention span, schizophrenia, and addiction withdrawal. These dangers are associated with the prolonged use of marijuana, and may cause permanent damage. Marijuana is known to contain more of some cancer causing agents than filtered tobacco cigarettes.
People who smoke marijuana can potentially inhale three times as much tar and may retain one third more tar in their lungs than tobacco smokers. The carbon monoxide level in marijuana smokers was five times as high as tobacco smokers as well. Compared to cigarette smokers and non-cigarette smokers, people who smoke marijuana show reduced airway function. The loss of function was worse among people who smoked marijuana than it was in people who smoked cigarettes. Marijuana smokers have a lesser ability to fight off infections and cancer.
After smoking marijuana, the cells in the lungs that breakdown and fight disease become unable to destroy “staphylococcus”, or strep throat. In addition, a lack in the ability to kill tumor cells was prevalent, as well as the inability to produce “interleukins” and other cancer killing biochemicals. Another aspect of the dangers of marijuana is trouble breathing, or asthma. Some people are allergic to cannabis pollen, resulting in asthma and inflammation of the throat. In a test was given in Nebraska, 122 people were given skin tests for cannabis pollen and other allergens.
Forty-eight of the 122 tested positive for cannabis pollen, and of the forty eight who tested positive, twenty two experienced respiratory symptoms during the test period. Cannabis may also affect brain functions. THC disrupts the nerve cells in the part of the brain where memories are formed. This makes it hard for the user to recall recent events (such as what happened a few minutes ago), and as such it is hard to learn while high. A working short-term memory is required for learning and performing tasks that call for more than one or two steps.
Some studies show that when people have smoked large amounts of marijuana for many years, the drug takes its toll permanently on mental functions. Among a group of long-time heavy marijuana users in Costa Rica, researchers found that the people had great trouble when asked to recall a short list of words (a standard test of memory). People in that study group also found it very hard to focus their attention on the tests given to them. It may be that marijuana kills some brain cells. In laboratory research, some scientists found that high doses of THC given to young rats caused a loss of brain cells such as that seen with aging.