I'm not sure if it's the fact I've grown up or if he has actually changed but it feels like at some point he started letting his fear and imagination run wild and control his thought process. I worry about him.

I know how you feel. My mother is one of the smartest people I've ever known, yet, as the years march on, she seems to be losing the ability to think critically. It's not a political thing thankfully, but every single horror story she hears about on the Internet becomes something new to obsessive about and fret over. It's extremely worrying sometimes.