Bipolar disorder in adults can often be accompanied by delusions and/or hallucinations (psychoses) but there has been little research into the prevalence of psychoses in children with bipolar disorder. A study of 257 children with bipolar disorder in the U.S. found that 76.3% of them had some form of psychosis. 38.9% of them had delusions, 5.1% had pathological hallucinations and 32.3% had both. The most common delusions were grandiose and the most common pathological hallucinations were visual. Benign hallucinations occured in 43.6%. Psychosis was equally prevalent in 6-9, compared to 10-16 year olds.
Tillman, Rebecca ... [et al] - Psychotic phenomena in 257 young children and adolescents with bipolar I disorder : delusions and hallucinations (benign and pathological) Bipolar Disorders February 2008, 10(1), 45-55