Mental health conditions alarmingly high among children with autism, study finds. Nearly 78 per cent of children with autism have at least one mental health condition and nearly half have more than that, according to a new study. Mental health conditions were present in 44.8 per cent of pre-school age children with autism -- a group among which prevalence had not previously been established using a large, population-based sample. Only 14.1 per cent of children without autism (Ages 3-17) had mental health conditions. Source 6p.