Something like that is hard to gauge, if people are getting paranoid from smoking can they carry on it could lead to all sorts of mental health problems in later life if they carry on.
It can take weeks or months maybe even longer depending on how heavy smoker that person was. I believe it's to do with cannabis affecting the chemical balance of the brain. If you're having these problems I suggest visiting your local doctor and getting advice if you are feeling very anxious about this. Try not to worry as I'm sure it will pass. In the majority of people I've come across who have had a similar experience have always found things returned to normal in its own time.
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