Some people may develop temporary psychotic symptoms, such as hallucinations and delusions, which resolve themselves within hours or a few days without any help. People who experience these temporary effects do not normally come to the attention of psychiatric services.
Previously, if a person was known to be a heavy cannabis user, and came to psychiatric services with a psychotic condition, the term "cannabis psychosis" was used. Often these problems turned out to be long-lasting, and the person developed enduring severe mental illness. However, we have now found that these cases should be diagnosed according to person's symptoms, including their use of cannabis which could be a possible trigger for psychosis.
It may be this group of people are particularly vulnerable to the effects of cannabis, and so should probably avoid it in the future.