Sometimes meds unfortunately cause what they are supposed to "cure"... its not very common I don't think, but some people become suicidal from anti-depressants, and some people like my sister experence regular panic attacks when using a benzo...

So while I have no idea if lithium can or has caused your son's symptoms, I wouldn't say these things are impossible. Maybe the symptoms would've manifested anyway, maybe not, the only way to know for sure is to drop the med.

But pdoc's generally don't advise doing so unless they feel sure the med is at fault, and even then some pdocs, like my former one, who refused to discontinue my lithium even though it made me retarded, will rather chuck more meds at you than drop the one causing problems.

If he's not already on one, his pdoc will probably suggest an anti-psychotic as opposed to tapering off lithium and trying a new mood stabilizer, because hallucinations aren't at all uncommon with bipolar.

Sooo I guess what I'm saying is speak to his doctor regarding a solution. Sorry I couldn't be of more help.