How Marijuana Works

Along with the brain, the side effects of marijuana reach many other parts of the body. Overall, users may notice the following short-term side effects:

The initial effects created by the THC in marijuana wear off after an hour or two, but the chemicals stay in your body for much longer. The terminal half-life of THC can range from about 20 hours to 10 days, depending on the amount and potency of the marijuana used. This means that if you take 1 milligram of THC that has a half-life of 20 hours, you will still have 0.031 milligrams of THC in your body more than four days later. The longer the half-life, the longer the THC lingers in your body.

The debate over the addictive capacity of marijuana continues. Ongoing studies now show a number of possible symptoms associated with the cessation of marijuana use. These symptoms most commonly include irritability, nervousness, depression, anxiety and even anger. Other symptoms are restlessness, severe changes in appetite, violent outbursts, interrupted sleep or insomnia. In addition to these possible physical effects, psychological dependence usually develops because a person's mind craves the high that it gets when using the drug.

Beyond these effects, marijuana smokers are susceptible to the same health problems as tobacco smokers, such as bronchitis, emphysema and bronchial asthma. Other effects include dry mouth, red eyes, impaired motor skills and impaired concentration. Long-term use of the drug can increase the risk of damaging the lungs and reproductive system, according to the U.S. Drug Enforcement Agency (DEA). It has also been linked to heart attacks.

Although marijuana is known to have negative effects on the human body, there's a raging debate over the use of medicinal marijuana. Some say that marijuana should be legalized for medical use because it has been known to suppress nausea, relieve eye pressure, decrease muscle spasms, stimulate appetite, stop convulsions and eliminate menstrual pain. Because of its therapeutic nature, marijuana has been used in the treatment of several conditions:

Others believe the negative effects of marijuana usage outweigh the positive. As of February 2014, in contrast to moves by several states toward medical marijuana statutes, the U.S. Drug Enforcement Agency listed marijuana as Schedule 1 substance. Schedule 1 is reserved for "the most dangerous drugs," substances with "no currently accepted medical use and a high potential for abuse... [and] potentially severe psychological or physical dependence," including heroin, LSD and Ecstasy.