Paranoia can be an effect of many recreational drugs, including marijuana, cocaine, meth and bath salts. It can also be a symptom of mental illness. And probably the worst thing about it is that it can stop you from getting help when you need it.
When you are high or withdrawing from drugs, seeking help can seem scary. What if they report you to the police? Rest assured, this is very unlikely to happen. When you go to an emergency room for treatment, all the staff care about is helping you to feel better. They don't routinely report drug users to the police, and they could save your life.
Doctors can also give you treatment for mental health problems that can cause paranoia, and in particular, psychosis.
So even if you feel paranoid, don't hold back from seeing your doctor or going to the hospital if you don't feel well after using drugs, or if you want to get help with quitting drugs. They are there to help you, not to judge you or to get you into trouble.