Marijuana smoke contains some of the same ingredients in tobacco smoke that can cause emphysema and cancer. In addition, many marijuana users also smoke cigarettes; the combined effects of smoking these two substances creates an increased health risk. "Burnout" is a term first used by marijuana smokers themselves to describe the effect of prolonged use. Young people who smoke marijuana heavily over long periods of time can become dull, slow moving, and inattentive. These "burned-out" users are sometimes so unaware of their surroundings that they do not respond when friends speak to them, and they do not realize they have a problem.
Scientists believe that marijuana can be especially harmful to the lungs because users often inhale the unfiltered smoke deeply and hold it in their lungs as long as possible. Therefore, the smoke is in contact with lung tissues for long periods of time, which irritates the lungs and damages the way they work.
Some human studies have also demonstrated withdrawal symptoms such as irritability, stomach pain, aggression, and anxiety after cessation of oral administration of tetrahydrocannabinol (THC), marijuana's principal psychoactive component. Researchers have shown that individuals who regularly smoke marijuana experience withdrawal symptoms after they stop smoking the drug. Studies at Columbia University in New York City have demonstrated that, in addition to aggression, marijuana smokers experience other withdrawal symptoms such as anxiety, stomach pain, and increased irritability during abstinence from the drug. These results suggest that dependence may be an important consequence of repeated daily exposure to marijuana.
Smoking marijuana burns up an enormous amount of vital nutrients in a person's body, which is a contributing factor in a pot smoker having "the munchies." Due to repeated use, a mariajuana user's body becomes very depleted of natural supplements and becomes much more prone to accidents, illness and disease by not having a proper healthy reaction to exposure.
Marijuana residues, like other toxic substances, store in the fatty tissue of a person's body and can continue to cause adverse reactions over an extended period of time, including physical cravings for the drug, slowed or dulled senses or memory and prolonged withdrawal symptoms of anxiety and more.