Co-Occurring Mental Health Conditions: When It’s Not ‘Just Autism’
A clinician who attributes every symptom to autism isn’t being thorough. They’re skipping the exam. This single diagnostic habit causes more untreated suffering than almost anything else in this field.
That single direct question forces a provider to distinguish between an actual differential diagnosis and a default assumption. It’s the fastest way to interrupt diagnostic overshadowing in a single appointment.
Diagnostic overshadowing, defined
The documented clinical tendency to attribute all of a person’s symptoms to their known disability, missing a separate, treatable condition underneath.
The numbers are not small
Anxiety at 40-50%, depression at 20-30%, and elevated OCD and PTSD rates all represent common, not rare, co-occurring realities.
Behavioral communication gets systematically ignored
A depressed or anxious Level 2/3 adult often can’t say so directly. The behavior that communicates it gets labeled ‘just autism’ instead.
Presentation looks different here
Depression might look like increased self-injury rather than verbalized sadness. Anxiety might look like rigidity rather than reported worry.
Treatment considerations differ too
Standard treatment protocols sometimes need real adaptation for this population, not simple substitution of medication alone.
Advocacy language changes outcomes
A specific, direct request for mental health assessment gets taken more seriously than a general concern about ‘behavior changes.’
Co-occurring condition rates in autistic adults
Estimated 40-50% prevalence
Estimated 20-30% prevalence
Elevated rates compared to general population
High rates, often linked to medical or systemic trauma
Diagnostic overshadowing suppresses recognition across all four
Grant’s withdrawal from activities he’d previously enjoyed was attributed, by three different providers over two years, to a natural autism-related preference shift. A fourth provider asked one specific question: had anyone actually screened for depression using a tool adapted for his communication style. Nobody had. He met criteria clearly. Treatment brought back activities and engagement that had quietly disappeared for two years, mistaken the entire time for simply who he was.
When you suspect something beyond autism itself, here is how to advocate
Escalation ladder
- 1Ask directly whether a co-occurring condition has been ruled out or assumed away.
- 2Request screening using tools adapted for limited verbal communication.
- 3Document specific behavioral changes, with dates and context.
- 4Ask what would be different about the treatment plan if this weren’t autism.
- 5Seek a second opinion if diagnostic overshadowing seems to be happening.
- 6Revisit the mental health question periodically, not as a one-time check.
Have ready
- A log of specific behavioral changes, with dates and context
- A direct question ready for your provider about ruling out co-occurring conditions
- Awareness of adapted screening tools for limited verbal communication
- A second-opinion provider identified in advance, if needed
- Patience; this often takes more than one appointment to resolve
“That’s just his autism” is sometimes true. It’s also, far too often, a diagnosis nobody actually made. Ask the question that forces the distinction.
Grant had stopped joining family game nights, stopped requesting his favorite music, stopped doing half a dozen small things that used to define an ordinary Tuesday for him, and three different providers across two years each offered some version of the same explanation: this is likely just a natural shift in his autism-related preferences, nothing to be concerned about specifically. A fourth provider asked a single different question, whether anyone had actually screened him for depression using an assessment tool adapted for his communication style. Nobody had. He met the criteria clearly, and had for some time.
What diagnostic overshadowing actually is
Diagnostic overshadowing is the well-documented clinical tendency for providers to attribute every symptom a person presents with to their known disability, autism in this case, without adequately investigating whether a separate, treatable condition is actually present underneath. This isn’t a rare clinical failing. It’s a documented, common pattern, and it means real, treatable suffering routinely goes unaddressed because a symptom got filed under a diagnosis that was never actually confirmed for that specific presentation.
Why the numbers matter
Estimates place anxiety disorder prevalence in autistic adults at 40 to 50 percent, depression at 20 to 30 percent, with elevated rates of OCD and PTSD as well, figures dramatically higher than general population rates. These aren’t rare co-occurrences to be considered only after exhausting every other explanation. They’re common enough that active screening should be a routine part of care, not an afterthought.
How presentation differs in Level 2/3 adults
Depression might present as increased self-injury or complete withdrawal rather than verbalized sadness. Anxiety might present as rigid insistence on routine or increased meltdowns rather than reported worry. A provider unfamiliar with how these conditions manifest behaviorally in this population, rather than verbally, is far more likely to misattribute the presentation entirely to autism itself.
Advocacy language that actually moves the conversation
Asking a provider directly, ‘have you ruled out a co-occurring condition, or assumed this is autism,’ forces an explicit answer rather than allowing a vague, comfortable default to stand unchallenged. Requesting screening tools specifically adapted for limited verbal communication, rather than standard self-report questionnaires that assume verbal fluency, also meaningfully changes what a provider is actually able to assess.
Grant wasn’t simply becoming a quieter version of himself. He was depressed, for two years, while three providers each filed it under a diagnosis he’d had since childhood. Ask the question that separates the two. It’s the single most impactful question in this entire field.
Jim Palasty is the founder of OASIS for Autism and a single father of an adult autistic daughter in Michigan.