Formal thought disorder in childhood onset schizophrenia and schizotypal personality disorder.

The Kiddie Formal Thought Disorder Rating Scale (K-FTDS) was examined in a sample of 29 schizophrenic, 10 schizotypal, and 54 normal children, aged 5-12.5 yrs. The schizophrenic and schizotypal children had significantly more illogical thinking and loose associations than the normal children. There were no significant differences between the illogical thinking and loose associations ratings of the schizophrenic and schizotypal children. Young schizophrenic, schizotypal, and normal children had more illogical thinking and loose associations than older children in their respective groups. The diagnostic, developmental, and cognitive implications of the study's results are discussed.