Co-occurring Psychiatric Disorders in Preschool and Elementary School-Aged Children with Autism Spectrum Disorder.

Salazar et al. (2015) asked one clear question: how many young autistic kids also meet criteria for another psychiatric disorder? They looked at 101 preschool and elementary-school children already diagnosed with autism spectrum disorder.

The team used standard surveys and checklists to spot anxiety, ADHD, specific phobias, and other conditions. No new treatment was tested; they simply counted what was already there.

Nine out of ten children (90.5 %) qualified for at least one extra psychiatric diagnosis. Anxiety disorders, ADHD, and specific phobias topped the list.

The message is blunt: if you work with young autistic clients, expect extra diagnoses as the rule, not the exception.

Llanes et al. (2020) extends these numbers by showing parents and teachers often disagree on the same anxiety and ADHD symptoms. Low parent-teacher match means you need both views before you decide whether to assess further.

Waldron et al. (2023) zooms in on preschool anxiety alone and finds a lower but still high 40 % rate. The gap looks like a contradiction, but it closes when you note Fernando counted any anxiety diagnosis while A required 'impairing' anxiety. Method tweak, not true conflict.

Mattila et al. (2010) is a close predecessor: 74 % of older autistic youth (8–18 yrs) carried extra diagnoses. Fernando’s 90 % in younger kids suggests comorbidity starts early and stays high.

For BCBAs, the 90 % figure is a planning tool. Build time into your intake to screen for anxiety, ADHD, and phobias. When behaviors spike, ask which diagnosis is driving the burst. Share the high base rate with parents so they are not surprised if you recommend extra evaluations. Treating autism without addressing the co-occurring condition is like mowing weeds: they grow back fast.