Concerta and adhd

My 8 year old son was started on Concerta a few months ago, has severe ADHD & Bipolar Disorder Type 2. He has become more agitated, very short fuse with 7 year old brother, hallucinations - visual of a movie thats coming out - kinda like a harry potter but more creepy, but I'm not sure if it is the concerta or the combo w/ his celexa and risperdal. I increased his risperdal from .75 mg to 1 mg, and it seems to help. He has alot of personal things going on also that could be contributing, any ideas if this could be the concerta or the combo? His Dr is having us get an MRI and a Neurophysical exam to rule out anything physical causing the effects, wants to cover all bases before changing meds. Any feedback welcome (he has been on the celexa and risperdal for a few years now and I know they are not the cause, I have extensive experience with these two meds, just not the concerta) We have also tried Strattera, but it made him too sleepy as it is a non stimulant. Thank you