All types of marijuana contain THC (delta-9-tetrahydrocannabinol) which is the main active chemical in the drug. Marijuana's effects on the user depend on it's strength or potency, which is related to the amount of THC it contains. The THC content of marijuana has been increasing since the 1970s. Marijuana can stay in the user's system for several days or several weeks depending on frequency and potency of the drug. The effects on the individual user often vary. The short-term effects of using marijuana are loss of motor coordination which includes clumsiness and stumbling. There is distorted perception as in time, sights, smells and touch. An increased heart rate may also be present along with trouble thinking, problem solving and learning. The short term effects usually last up to a couple hours and cause drowsiness after the immediate effects have worn off. The effects of marijuana can be magnified if mixed with other drugs or alcohol. It can often be laced or contaminated with other drugs. This can also alter the effects on an individual.
Long-term effects of marijuana can be more serious and damaging than the short-term effects. Marijuana may also promote cancer of the upper digestive tract. Some reports note an increase in cancer of the tongue in people who smoke marijuana but who have no other risk factors. Normally, such cancers are rare in people under age 60. It has come into question though whether or not weed or pot can cause cancer but there is more evidence for medical studies supporting this theory. It is known that marijuana contains some of the same, and sometimes even more, of the cancer-causing chemicals found in tobacco smoke. Studies show that someone who smokes five joints per day may be taking in as many cancer-causing chemicals as someone who smokes a full pack of cigarettes every day. Smoking marijuana may also cause breathing problems such as wheezing and coughing.