Stimulants like Concerta do tend to make children's bipolar disorder worse. The biggest thing is why he has mood swings. If he's only having mood swings that correlate to a sensory issue, disruption in routine/change, or "special interest," then this is the autism. If, however, he's having pervasive mood swings (for example, always being depressed, no matter what the circumstance is), then this indicates possible bipolar disorder. Bipolar people cannot "switch" off their moods. Autistic mood swings are turbulent, but usually quick-lived; bipolar mood swings are not. Plus, if you see any obvious psychotic symptoms, then this definitely suggests bipolar mania. You should definitely ask your son's psychologist to analyze his behavior thoroughly to determine whether he does indeed have comorbid bipolar disorder. Good luck, God bless, and if you have any questions, feel free to ask!