Autism vs. OCD

Autism vs. OCD

How to tell the difference when routines, repetition, and rigidity look the same

I’ve conducted over 2,000 evaluations—autism, ADHD, learning disorders, and everything in between. One of the most common questions I hear (from parents and adults) is:

“How do you tell the difference between OCD and autism?”

Because on the surface, they can look identical.

Both can involve:

• routines and sameness

• repetitive behaviors

• distress when something changes

• intense focus and “getting stuck”

• anxiety spikes when the environment feels unpredictable

But the reason behind the behavior—the “why”—is often completely different.

I’m Dr. James Thatcher, a licensed psychologist at Forest Psychological Clinic in the Portland metro area. This article is educational and not medical advice. By the end, you’ll understand what a good evaluator is looking for, how to spot key differences in yourself or a loved one, and why it’s also possible (and common) to have both.

Why autism and OCD get confused so often

Two big reasons:

1) They share visible behaviors

From the outside, an autism routine and an OCD ritual can both look like:

• “They have to do it a certain way”

• “They melt down if it changes”

• “They repeat the same thing”

• “They get stuck and can’t move on”

2) They can co-occur

Research consistently shows meaningful overlap between autism and OCD. A 2024 systematic review/meta-analysis focused on children and adolescents reported on the prevalence of OCD among autistic youth and the prevalence of autism among youth with OCD, highlighting clinically significant co-occurrence. PMC+1

You’ll sometimes see ranges quoted like ~17%–37% in youth samples depending on methods and definitions. Medical News Today+1

So yes—this is a real diagnostic challenge, even for clinicians.

What OCD actually is (in plain language)

OCD = Obsessive-Compulsive Disorder. It has two main components, though people can have one dominate the picture.

Obsessions

Obsessions are recurrent, intrusive, unwanted thoughts/urges/images that cause distress. DSM-aligned definitions emphasize that these thoughts are experienced as intrusive/unwanted and typically create anxiety or distress. NCBI+1

A key word many adults relate to is ego-dystonic: the thought feels not like you, not aligned with your values, often shocking or upsetting.

Examples (not exhaustive):

• “What if I contaminate someone?”

• “What if I hit someone with my car and didn’t notice?”

• “What if something terrible happens because I didn’t do this ‘right’?”

• taboo intrusive thoughts that create shame and fear

Compulsions

Compulsions are repetitive behaviors or mental acts a person feels driven to do to reduce distress or prevent a feared outcome. The DSM framework describes compulsions as behaviors/mental acts aimed at reducing anxiety or preventing something dreaded, even if they’re excessive or not realistically connected. NCBI+1

Examples:

• washing, checking, repeating, reassurance-seeking

• mental reviewing, counting, praying “just right,” rumination (yes—compulsions can be internal)

Short-term relief → long-term strengthening of the cycle is the OCD trap.

What autistic “rigidity” and repetition usually are (also in plain language)

Autistic routines and repetition are often:

• structure-based

• predictability-based

• sensory-based

• meaning-based

• regulation-based

In other words: not a desperate attempt to neutralize an intrusive thought—but a way the brain organizes experience so the world feels understandable and manageable.

An autistic person might:

• line up objects

• repeat a movement (stimming)

• follow a routine the same way daily

• insist on rules

• replay a favorite topic/interest

because it provides stability, comfort, and regulation.

The International OCD Foundation has an excellent clinician-facing discussion of this confusion: autism can involve restricted interests and routines that resemble OCD, but the underlying distress/meaning often differs. International OCD Foundation

The AANE also notes how sensory-motor behaviors in autism can look like OCD-related behaviors at first glance. aane.org

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The core distinction I use in evaluations

Same behavior. Different engine.

Here’s the simplest way I explain it:

OCD: “I have to do this, otherwise something bad might happen”

Autism: “I do this because it helps my brain make sense of the world / feel regulated / feel safe”

Or even more cleanly:

OCD behaviors fight anxiety.

Autistic behaviors organize experience (and often reduce overload).

That’s why two people can do the same outward behavior—say, repeating a phrase, arranging items, insisting on a routine—and yet the diagnosis differs.

A practical “why” checklist: OCD vs autism

Here are the questions I’m implicitly asking when I see repetitive behavior or rigidity:

1) Is there an intrusive fear thought driving it?

• “What thought shows up right before you do the behavior?”

• “What are you afraid will happen if you don’t do it?”

• “Do you feel compelled, pressured, trapped into it?”

If the person describes a fear-based obsession that the behavior neutralizes
→ OCD becomes more likely. NCBI+1

2) Is it ego-dystonic or ego-syntonic?

• OCD obsessions are typically unwanted and distressing (ego-dystonic).

• Autistic routines/interests are often experienced as aligned, comforting, regulating (more ego-syntonic), even if the person is distressed when disrupted.

(Important nuance: autistic people can also feel distressed by their rigidity—especially if it causes impairment. The question is still: what’s driving it?)

3) What happens emotionally after the behavior?

• OCD: temporary relief, then the fear returns and demands the ritual again.

• Autism: regulation, comfort, predictability; distress spikes mostly when routines are disrupted or sensory load is high.

4) Is it about “just right” + catastrophic prevention?

OCD often includes a “just right” feeling or fear that something terrible will happen without completion or exactness.

Autistic insistence is more often about:

• predictability

• fairness/rules

• sensory comfort

• transition support

• cognitive clarity (“this is the system that makes sense”)

5) Can the person flex with support?

Both can be inflexible. But the kind of flexibility support differs:

• OCD: flexibility requires treatment that targets the obsession-compulsion loop (often ERP-style work).

• Autism: flexibility often increases with predictability supports, sensory accommodations, and scaffolding transitions.

The “gray zone”: when both exist (and it gets confusing fast)

It’s not either/or. Autism and OCD can co-occur, and when they do, it can be hard to tell which symptoms belong to which.

A common pattern: an autistic child has baseline rigidity and sensory overwhelm, and then develops OCD-like intrusive fears and compulsions on top of that.

Or an adult has lifelong autistic traits and later develops OCD (or vice versa).

This is why you can’t diagnose based on one symptom like “needs routine.”

A real-life example that shows the difference

OCD-driven school avoidance

A child has intrusive fear: “Something bad will happen at school.”

They can’t fully explain the fear. It’s just intense, sticky, and distressing.

The compulsion becomes avoidance:

• “I’m not going.”

• staying home provides relief

• next day the thought returns stronger

• the avoidance becomes reinforced

That pattern fits the OCD cycle logic: distress → compulsion → relief → stronger return. NCBI+1

Autism-driven school avoidance

A different child avoids school because:

• sensory overload (noise, crowds, lights)

• social confusion and burnout

• unpredictable transitions

• executive functioning overload

• repeated meltdowns/shutdowns at school

This isn’t about neutralizing an intrusive thought. It’s about overload and mismatch.

Same behavior (avoid school). Different engine.

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What a good evaluator looks for in testing

In my evaluations, I don’t just look at what is happening. I look at:

1) Pattern across settings

• Home vs school vs community

• Does it show up everywhere or only under certain stressors?

2) Developmental timeline

• Did the rigidity/repetition show up early in life?

• Were there early autistic markers (social-communication differences, sensory profile, restricted interests, stimming, early play patterns)?

3) Function of behavior

This is the big one:

Is this behavior trying to stop an unwanted intrusive thought? (OCD)

or Is this behavior creating structure/comfort/regulation? (autism)

4) Multi-informant data

Good evaluations don’t rely on a single conversation. They pull from:

• parent interview

• teacher input (when relevant)

• self-report (especially for teens/adults)

• behavioral observations

• rating scales and adaptive measures (e.g., behavior and daily living supports)

And importantly: a strong evaluator knows the limitations of any single test and uses results as part of a whole clinical picture.

Common myths I still hear

Myth 1: “If you have OCD, you can’t have autism.”

False. Co-occurrence is well-documented, and clinicians should actively consider both when symptoms overlap. PMC+1

Myth 2: “All repetitive behaviors are compulsions.”

Also false. Many repetitive behaviors—especially in autism—are sensory-based, self-soothing, regulating, or interest-driven. aane.org+1

Myth 3: “If it reduces anxiety, it must be OCD.”

Not necessarily. Autistic routines often reduce anxiety because predictability regulates the nervous system. The key difference is whether there’s an intrusive obsession being neutralized.

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The key takeaway

Both autism and OCD can involve repetition and rigidity. Both can reduce anxiety.

But the mechanism is different:

• OCD rituals are driven by distressing intrusive thoughts and are performed to neutralize fear. NCBI+1

• Autistic routines/repetition more often organize experience, support predictability, and regulate sensory/cognitive load. aane.org+1

That distinction matters because it changes what “help” looks like.

Questions to ask your evaluator (to get a clearer answer)

If you’re pursuing an assessment for yourself or your child, here are questions that tend to separate “quick opinions” from careful differential diagnosis:

1. Are you assessing for autism, OCD, or both?

2. How will you determine function—what’s driving the routines or repetitive behaviors?

3. Will you assess for intrusive thoughts/obsessions directly (including mental compulsions)?

4. Will you look at developmental history to determine what has been lifelong vs. what emerged later?

5. If both are present, how will recommendations differ? (supports, accommodations, therapy approach)

Want support with an autism/ADHD evaluation or diagnostic clarification?

If you’re in the Portland metro area and want to learn more about comprehensive evaluations through Forest Psychological Clinic:

https://forestpsychologicalclinic.com

References

• Systematic review/meta-analysis on ASD–OCD concurrence in youth (prevalence estimates vary by method/sample). PMC+1

• OCD definitions aligned with DSM descriptions of obsessions/compulsions (intrusive unwanted thoughts; compulsions reduce distress). NCBI+2Beyond OCD+2

• International OCD Foundation expert opinion on differentiating autism routines/restricted interests vs OCD distress-driven obsessions/compulsions. International OCD Foundation

• AANE overview: autism sensory-motor/repetitive behaviors can resemble OCD; function matters. aane.org

• Public-facing summary noting reported ranges like 17%–37% in some youth research summaries (use cautiously; underlying studies differ). Medical News Today+1