I have a close relative, in his late 60's, who has become paranoid about his neighbors. He thinks they are watching him and spying on him to the point he no longer goes in his yard (he will leave the house though). He is highly sensitive to noise... believing every loud noise outside is directed at him (slamming doors, barking dogs, leaf blowers). Otherwise he is completely sane and normal, no other symptoms of mental distress. He is highly intelligent, too. He has a history of alcohol abuse (perhaps to quiet the paranoia?) but is drinking much less now... about a drink or two max a night. The paranoia exists all the time, regardless of alcohol consumption He is also aware people think he is "crazy" but he firmly believes he is being spied on. I fear his paranoia will extend to others, maybe even his family. Although he shows zero signs of violence, thankfully. Also, not sure if this is relevant, but there is history of pedophile in his family, and I'm wondering if he may have been one of the victims. There have also been suicides.
Any info you have on what this may be and what to do would be helpful.