Is it normal for people with a psychiatric illness to be more sensitive to caffeine?

Caffeine problem: It depends on the problem., people who are anxious or have insomnia should avoid caffeine. The effects last many hours and cause sleep issues. I find that people with adhd often overuse caffeine in an attempt to treat symptoms. Unfortunately, this doesn't work so well and too much caffeine is hard on your body. It increases anxiety, speeds up heart rate and interferes with sleep.

Caffeine: Caffiene sensitivity is Adenosine based and genetic also, if your brain produces lot of Adenosine you may need higher amounts to compensate for sleepiness if not then lower amounts.