A natural way to reduce paranoia is to increase GABA and GABA building blocks in your diet. Almonds are a great example, and I take lots of supplements to also help w/ Gaba quantity (my Gaba receptors aren't peak functional). I've had times I've tapped out my Gaba reserves (internally) and paranoia would flourish.

It might allow you to try Ritalin again (albeit in smaller doses).