For some people, the paranoia is more or less something that you initially experience when you first start smoking and then you become acclimated to the sensations created by smoking and learn how to relax and enjoy yourself in that state. In other words it's someting that you work past or overcome.

For other people, they tend to continue to experience paranoia and that could be more so a reflection of their current state of being or personality. I would say cannabis can tend to enhance or amplify feelings that already exist within you - so if you are a paranoid or anxious person by nature, then it's likely that smoking would facilitate those feelings being experienced and bring them to the surface.

Something else to consider, there are different 'types' of cannabis plants. Sativa/Indica. Sativa strains are known for giving you a cerebal and mentally energetic 'high' (so these might not be ideal for someone who is prone to anxious/nervous thoughts), Indica strains are known for producing a body 'high' (and less of a mental/cerebral high) - they are typically ideal for pain management and tend to make people more lethargic or just want to sit around and rest/relax. Then there are 'hybrid' strains which are the result of crossbreeding between sativa/indica strains to achieve a combination of the desired effects that two different strains might have to offer.