The most common co-occurrences
Large cohort studies consistently find that the majority of autistic people have at least one additional diagnosis (Lai et al., Lancet Psychiatry, 2019).
Mental health
- Anxiety disorders — ~40% of autistic people (van Steensel et al., 2011)
- Depression — substantially higher than non-autistic peers, especially in adulthood
- ADHD — estimated 30–80% co-occurrence (Hours et al., 2022)
- OCD — elevated rates; can be confused with autistic routines
- PTSD — higher rates, often from cumulative invalidation and sensory trauma
Neurological
- Epilepsy — ~20% across the lifespan (Bolton et al., 2011), with peaks in early childhood and adolescence
- Sleep disorders — 50–80% of autistic children (Souders et al., 2017)
- Tic disorders
Physical and medical
- GI conditions — 4× higher rates of chronic GI symptoms (McElhanon et al., 2014)
- Ehlers-Danlos syndrome / joint hypermobility — emerging strong association (Csecs et al., 2022)
- PMDD in menstruating autistic people (Obaydi & Puri, 2008)
- Migraine
Other neurodevelopmental
- Intellectual disability — co-occurs in roughly 35% (CDC ADDM Network, 2023)
- Learning disabilities (dyslexia, dyscalculia)
- Developmental coordination disorder (dyspraxia)
Why this matters
Many "behavior" problems are actually untreated co-occurring conditions:
- Self-injury can signal pain (ear infection, migraine, GI)
- "Aggression" can signal undiagnosed ADHD impulsivity
- Increasing meltdowns can signal sleep apnea or PMDD
What to do
- Ask any new diagnosing clinician about screening for ADHD, anxiety, GI, sleep, and EDS
- Treat the co-occurring condition specifically — autism support alone won't resolve untreated migraines, for example
- Track patterns: a symptom diary often surfaces a missing diagnosis