Yes, there's a difference. And it depends on your perspective, of course. But a deluded person is just someone who feels like they understand all the "facts" and who's judgement/opinion is based off of that. A conspiracy theorist isn't necessarily deluded - they can believe the government is getting technology from aliens but the difference is that conspiracy theorists believe that its being hidden from the public. For instance, a democrat is likely to consider the typical republican "deluded," …
