Sometimes people become quiet and reflective. They may also become sleepy. People can lose track of what they were thinking or saying. When affected by cannabis some people may feel as though they have had profound ideas or insights. It can affect vision and perception of time and space.
Hallucinations can also occur.
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.