Common Co-Occurring Conditions: What Else Often Comes With Autism
Published May 12, 2026
Most autistic children have one or more co-occurring conditions — ADHD, anxiety, GI issues, sleep disorders, intellectual disability, and others. A guide to what to watch for, when to seek assessment, and which conditions are commonly missed.
Common Co-Occurring Conditions
Autism rarely travels alone. Most autistic children have one or more co-occurring conditions — sometimes diagnosed alongside autism, often missed for years because attention is on the autism diagnosis itself.
This guide is a survey of the conditions most commonly missed and what to watch for. It's information, not diagnosis. If you recognize signs in your child, the next step is a conversation with their doctor.
ADHD
The most common co-occurring condition with autism — research estimates 30–80% of autistic children also meet ADHD criteria. The combination is sometimes called "AuDHD."
What it looks like: - Difficulty sustaining attention to non-preferred tasks - Impulsive actions (interrupting, grabbing, eloping) - Hyperactivity - Disorganization, forgetfulness - Difficulty with transitions and shifting attention
Why it matters: ADHD is treatable. Stimulants (methylphenidate, amphetamine-class) and non-stimulants (guanfacine, atomoxetine) help many AuDHD kids significantly.
When to ask: If your child shows clear hyperactivity or inattention that persists across settings, ask for ADHD assessment.
Anxiety disorders
Autistic children experience anxiety at rates 2–3x higher than typical peers. It often presents differently: - Refusal of activities or transitions ("won't" rather than "can't") - Repeated questions about future events - Increased rigidity around routines - Increased sensory sensitivity during stressful periods - Stomach aches, headaches, and other physical complaints - Sleep disruption tied to specific worries - Selective mutism
Treatment options: - CBT modified for autistic children - Exposure therapy — gradual, supported exposure to feared situations - SSRIs — antidepressants are often first-line for anxiety - Family interventions — reducing accommodations that maintain anxiety
Gastrointestinal issues
Significantly more common in autistic children.
Constipation
Far more common than people realize. Many autistic children eat low-fibre diets, drink too little water, and may not respond to typical bodily cues. Affects sleep, behaviour, toileting, and appetite.
What helps: more fibre, more water, more movement, sometimes a stool softener under pediatrician guidance.
GERD (acid reflux)
Common in younger children. Signs: morning cough, vomiting, refusal to lie flat, food refusal, irritability after meals.
What helps: smaller, more frequent meals; elevation during sleep; identification and removal of trigger foods (often dairy); medical treatment when needed.
Food selectivity / ARFID
See the dedicated guide on picky eating and ARFID.
Sleep disorders
Up to 80% of autistic children have meaningful sleep problems: - Insomnia — difficulty falling asleep or staying asleep - Sleep apnea — pauses in breathing, often with snoring; underdiagnosed - Restless legs / periodic limb movement - Circadian rhythm differences
The medical layer often missed: enlarged tonsils and adenoids cause sleep apnea in many children. Improvement after tonsillectomy/adenoidectomy can be dramatic.
Intellectual disability (ID)
Distinct from autism but co-occurs in some children.
Why it matters for parents: - ID identification opens additional supports. - It changes long-term planning. - It does not mean a child can't learn or have a meaningful life.
Important caveat: IQ testing is often unreliable in non-verbal or limited-verbal children. A child who scores in the ID range on standard testing may have significantly more cognitive ability than the test captures.
Epilepsy and seizures
Autism increases epilepsy risk. Estimates: 5–25% of autistic individuals will have a seizure disorder at some point.
Types most commonly missed: - Absence seizures: brief episodes of staring blankly, sometimes with subtle eye fluttering. Easily mistaken for inattention. - Focal seizures: brief twitching or unusual sensations. - Tonic-clonic seizures: full-body convulsions. - Febrile seizures: triggered by fever.
When to ask: If you've noticed staring spells, unusual repetitive movements, or any seizure-like episodes, ask for a pediatric neurology referral.
OCD
A subset of autistic children have OCD layered on top of autism: - Autistic restricted interests: enjoyable. - OCD compulsions: distressing, the child feels compelled, can't stop.
Treatment: ERP (Exposure and Response Prevention) therapy and SSRIs are first-line.
Depression (especially in teens)
Adolescent autistic individuals have significantly elevated rates of depression and suicidal ideation, particularly: - Females - Those with higher cognitive ability who notice their differences from peers - Those experiencing social rejection or bullying
Signs: - Withdrawal from previously enjoyed activities - Sleep changes, eating changes - Talk of being a burden, hopelessness - Increased irritability - Self-harm or talk of self-harm
This is urgent. If your teen is showing signs of depression, especially with any mention of self-harm, contact your family doctor or a mental health crisis service. In Canada: Talk Suicide Canada — 1-833-456-4566.
Tic disorders
Some autistic children develop tics. Most are mild and transient. Tourette syndrome involves multiple motor and vocal tics for over a year.
Apraxia of speech
A motor-planning disorder where the brain has difficulty coordinating speech movements. Some autistic children have apraxia layered on top of autism.
Signs: - Inconsistent production of the same word - Sounds in isolation are fine, but combining them is hard - Significant gap between receptive and expressive language
A speech-language pathologist with apraxia experience can assess and treat.
Genetic syndromes
A subset of autistic children have an identifiable genetic syndrome (Fragile X, Rett, Angelman, tuberous sclerosis, others). Genetic testing through children's hospital metabolic-genetics clinics can be informative for severely affected children.
Sensory processing differences
Considered part of autism but worth mentioning because they drive much of what looks like "behaviour" and they can be specifically supported by occupational therapy.
What every parent eventually learns
- Autism rarely travels alone.
- Treating co-occurring conditions can radically change quality of life.
- A good developmental pediatrician keeps a checklist of co-occurring conditions and screens for them periodically.
- Don't accept "they're autistic, that's just how it is" as the answer to symptoms that have other explanations.
- Trust your sense that something else is going on.
Your child has autism. They might also have several other things, each of which is treatable, manageable, and worth addressing.