Marijuana: Physiological effects

Last modified: Sunday, 31. May 2009 - 5:04 pm

While it is true that most people smoke marijuana precisely for its Mental effects, they may not be aware of the physical changes that accompany the high. One of the drug’s first effects is to raise the heart rate and blood pressure. The eyes become bloodshot and the pupils dilate; the mouth and throat also become dry. The appetite is stimulated, and users often become unusually hungry.
At the same time, the cannabinoids in marijuana, already at work in the hippocampus, bind to THC receptors in other parts of the brain, including the basal ganglia, which govern the body’s involuntary muscles, and the cerebellum, which controls coordination and sense of balance. These changes relax muscles all over the body, slowing reaction time and impairing the body’s ability to move efficiently. When the high wears off, fatigue and torpor replace the creativity and hyperawareness users may experience initially.
As the drug is broken down by the body, fat-soluble THC metabolites accumulate in the liver and other organs. Thirty percent of any one dose of THC is still in the body a week later, and smaller but still-detectable amounts are present two weeks after that. The more often marijuana is used, the greater the buildup in the body; heavy users’ urine may show traces of the drug more than a month after the last dose.
Harmful side effects
Despite a popular myth that cannabis use is harmless, marijuana smoke, like cigarette smoke, contains cyanide, as well as higher levels of benzopyrene and carbon monoxide. Marijuana joints the same size as a cigarette produce five times the carbon monoxide in subjects’ blood. Smoking marijuana produces three to four times the tar of tobacco, and more of it stays in the lungs. Because marijuana smoke is inhaled more deeply and held far longer in the lungs than tobacco smoke, damage to the delicate pleural tissues is as or more pronounced. Some researchers equate one joint to five cigarettes; others contend that three to four joints are as damaging as a pack of cigarettes.
Women who smoke marijuana during pregnancy may have low birth-weight babies who are at risk for developmental difficulties and are more susceptible to disease. Like other drugs, THC also crosses the placental barrier and affects the embryo as it grows; some studies indicate that this may increase a baby’s risk of developing leukemia. THC also passes into breast milk, where research has shown that it can affect a child’s motor development. Toddlers whose parents smoke marijuana have been found to be angrier and to have more behavioral problems than children whose parents do not use marijuana.
Long-term health effects
Marijuana smokers are at higher risk than nonusers for chronic lung diseases such as bronchitis, asthma, lung infections, and emphysema. Research also indicates that heavy marijuana use can lead to the DNA damage and cellular changes that produce lung cancer; these changes appeared to occur in marijuana smokers at an earlier age than in tobacco smokers. Cancers of the head and neck are also more common in marijuana smokers. People who smoke both marijuana and tobacco are at an even higher risk of serious disease.
In men, heavy long-term marijuana use can lead to lowered sperm counts and even impotence. It can also cause a hormone imbalance that leads to gynecomastia, the development of feminine breasts. Women who abuse marijuana may experience menstrual cycles that are off balance.

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