Even though THC can produce relaxation, if higher amounts are consumed, it can have the opposite effect by increasing anxiety. Some cannabis users may have unpleasant experiences, including confusion, hallucinations, anxiety and paranoia, depending on their mood and circumstances.
Some users may experience psychotic symptoms with hallucinations and delusions lasting a few hours, which can be very unpleasant. Even though these unpleasant effects do not last long, since the drug can stay in the system for some weeks, the effect can be more long-lasting than users realise.
Long-term use can have a depressant effect and reduce motivation. Some researchers also suggest that long-term use can lead to irreversible, but minor cognitive deficits.