So cannabis users have an increased risk of respiratory illness such as lung cancer and chronic bronchitis. The risk is increased because marijuana smokers often inhale deeply and hold the smoke in the lungs longer, to increase the effects of the drug. Cigarette smokers who smoke cannabis have an even greater risk of respiratory disease. Sometimes heavy and chronic use can cause a psychiatric condition called cannabis psychosis in vulnerable people. The symptoms of this condition are similar to the symptoms of schizophrenia.
Some regular users have less energy and motivation so that performance at work or school suffers.
Research shows that some cannabis users have a lower sex drive. Irregular menstrual cycles and lowered sperm counts have also been reported. The body gets used to functioning with the drug present. Heavy and frequent use of cannabis can cause physical dependence. People can become psychologically dependent on any drug, including cannabis.