What exactly does paranoid mean in terms of psychoactive drugs? When I went to my local marijuana dispensory, since recreational use of it is legal, they told me that when I first use it, I might get paranoid. When I read this word in context, I imagined somebody being afraid of getting caught. So, wouldn't you be paranoid if you didn't want other family members knowing that you smoked weed? Or, would this feeling or emotion be sharpened by THC?
Studies have shown that strong doses of THC can significantly increase paranoid thinking. See the article, "How Cannabis Causes Paranoia: Using the Intravenous Administration THC to Identify Key Cognitive Mechanisms Leading to Paranoia" by Freeman et al. for a more authoritative reference.

From the article:


  In this large study of intravenous THC (Schizophrenia Bulletin, Volume 41, Issue 2, 1 March 2015, Pages 391–399), it was definitively
  demonstrated that the drug triggers paranoid thoughts in vulnerable
  individuals. The most likely mechanism of action causing paranoia was
  the generation of negative affect and anomalous experiences.


And, certainly, anxiety over people “finding out” you are doing something that can be perceived as wrong or inappropriate can lead to paranoia.