One of the key symptoms of paranoia is a firm belief that other people intend to do harm to the patient, accompanied by a lack of trust in other people. Someone with paranoia is in a state of permanent delusion, with beliefs which cannot be shaken, despite ample evidence to the contrary. One of the big issues with the treatment of paranoia is that it can be difficult to get a patient to go to therapy or to find an acceptable therapist, due to deep-seated beliefs that everyone is out to get the patient, and is therefore not worthy of trust.
Paranoia can take a broad number of forms. Some people have classic persecutory paranoia, in which they believe that they are in danger from everyone else. Others might have litigious paranoia, in which they repeatedly attempt to sue people or threaten people with suit over perceived offenses, or they may suffer from reformatory paranoia, characterized by the belief that the patient needs to correct the behavior and beliefs of others. There are a number of other forms of paranoia, all of which revolve around a core belief which the patient believes is true, although it is not, and the symptoms of paranoia are usually similar, no matter what form it takes.
Distrust is the hallmark of paranoia. Someone who suffers from paranoia is very defensive, sometimes to the point of being aggressive, and may constantly question the motives of others. Even if people appear harmless on the surface, the paranoid patient believes that they are simply trying to lull the patient into a sense of complacency, and the patient will remain on guard as a result. Other symptoms of paranoia can include a sense of social isolation caused in part by the patient's defensive and suspicious behavior, and a lack of humor.
Paranoid patients are also hypersensitive. Casual comments or innocuous statements are perceived as personal attacks or insults by someone with paranoia, making extreme sensitivity one of the distinctive symptoms of paranoia, in addition to a diagnostic criterion. The onset of symptoms is usually gradual as the delusion becomes more deep-seated, and as the patient encounters opposition, concern, or confusion which reinforce the patient's beliefs that no one in the world is safe or trustworthy.
Because people with paranoia believe that other people intend to do them harm, when the symptoms of paranoia are identified, it is not necessarily a good idea to bring someone's attention to them, or to push someone to seek therapy or help. A paranoid patient will take these well-meaning attempts as hostile threats. It can help to consult a mental health professional for advice on dealing with someone who may have paranoia.