ADHD, Autism, and OCD: Why Intrusive Thoughts Are More Common in Neurodivergent Adults

By Tim Aiello, MA, LPC, NCC, ADHD-CCSP, ASDCS | Clinical Director | Myndset Therapeutics

If you live with ADHD, autism, or both, you probably already know our brains rarely stay inside neat diagnostic boxes. The way we process information, notice patterns, and hold onto thoughts can be intense, layered, and sometimes exhausting.

Over the years, both personally and in my clinical work, I’ve started noticing something that comes up more often than people realize: obsessive–compulsive patterns showing up alongside ADHD and autism. Not necessarily in the stereotypical ways people imagine OCD, but through intrusive thoughts, mental checking, and certain kinds of anxiety loops that feel impossible to shut off.

To be clear, I’m not presenting myself as an OCD specialist here. My work primarily focuses on ADHD and autism. What I want to do instead is open a conversation about something that many neurodivergent adults seem to experience, supported by what current research is beginning to show.

And the research suggests this overlap is real.

The Research Is Catching Up to What Many of Us Experience

For many years ADHD, autism, and OCD were studied as separate conditions. More recent research has started to show that these diagnoses overlap much more frequently than clinicians once believed.

Studies suggest that obsessive–compulsive symptoms occur in approximately 11–25% of autistic individuals, significantly higher than in the general population (Hollander et al., 2020). At the same time, ADHD traits are also common among individuals diagnosed with OCD. Some research estimates that up to 30% of individuals with OCD may also meet criteria for ADHD (Abramovitch et al., 2015).

Part of this overlap may be explained by shared brain circuitry. OCD is associated with dysregulation in cortico–striato–thalamo–cortical circuits, which influence habit formation, threat detection, and behavioral inhibition (Pauls et al., 2014). Interestingly, many of these same neural networks are implicated in both ADHD and autism.

In other words, these conditions may be interacting within similar neurological systems rather than existing in completely separate categories.

OCD Doesn’t Always Look the Way People Expect

When most people think about OCD, they picture behaviors like excessive handwashing or repeatedly checking locks.

Those are real experiences for some people, but OCD can also appear in ways that are much more internal. Many neurodivergent adults describe intrusive thoughts that feel disturbing, confusing, or completely out of character.

These thoughts are not chosen. They show up suddenly and tend to stick.

For individuals whose brains already lean toward deep thinking, pattern recognition, and mental replay, intrusive thoughts can sometimes get caught in loops that are difficult to interrupt.

Harm OCD

One pattern that occasionally appears is known as Harm OCD.

This involves intrusive fears about harming someone, harming oneself, or losing control in some catastrophic way. These thoughts are ego-dystonic, meaning they strongly conflict with the person’s identity and values.

For many neurodivergent individuals, this can feel especially upsetting because empathy and moral awareness are often very strong. The brain may start trying to analyze the thought, neutralize it, or prove that it isn’t true.

Unfortunately, that attempt to solve the thought can sometimes keep the loop going.

Health and Medical OCD

Another pattern sometimes involves intense anxiety around health or bodily sensations.

Neurodivergent individuals often experience differences in interoception, which refers to how we perceive internal body signals. A small sensation can feel confusing or alarming, leading to repeated symptom checking, medical research, or reassurance seeking.

ADHD can complicate this further. Once attention locks onto a health concern, hyperfocus may make it difficult to disengage from researching possible explanations.

What begins as curiosity can quickly turn into hours of searching for certainty.

Moral and Responsibility OCD

Some people experience intrusive doubts related to morality or responsibility.

These thoughts may sound like:

“Did I say something offensive?”“What if I hurt someone without realizing it?”“What if I’m actually a bad person?”

Many autistic and ADHD individuals care deeply about fairness, honesty, and doing the right thing. That strong moral awareness can be a beautiful trait. But when intrusive doubt attaches itself to those values, the brain may start seeking constant reassurance that nothing harmful occurred.

Other OCD Themes Sometimes Seen in Neurodivergent Adults

There are several other obsessive–compulsive patterns that occasionally appear in neurodivergent populations.

Relationship OCD (ROCD) involves intrusive doubts about one’s relationship or feelings toward a partner. Someone may repeatedly question whether they truly love their partner or whether the relationship is “right,” even when there is no real evidence of a problem.

Scrupulosity, sometimes referred to as moral or religious OCD, involves obsessive fears about being morally wrong, unethical, or spiritually flawed.

Contamination OCD can involve fears about germs, illness, or environmental contamination. In some cases this can overlap with sensory sensitivities or health anxiety, which can make the experience more complex.

These themes do not represent character flaws or hidden desires. They are examples of how intrusive thoughts can attach themselves to the things people care about most.

When OCD and Autism Look Similar

One reason this topic can be confusing is that OCD compulsions and autistic routines can sometimes look similar on the surface.

Both may involve repetition, predictability, or structured behaviors. However, the internal experience behind them is very different.

Autistic routines often feel calming and regulating. They provide structure and help the nervous system manage sensory and cognitive overload.

OCD compulsions, on the other hand, are typically driven by anxiety and fear. They are attempts to prevent something bad from happening or to reduce distress caused by intrusive thoughts. The relief they provide tends to be temporary, which is why the cycle continues.

Understanding this difference is important when determining what type of support may actually help.

The Nervous System Perspective

From a nervous system perspective, obsessive–compulsive patterns can be understood as the brain attempting to resolve perceived threat.

When the brain interprets a thought as dangerous or unacceptable, it may attempt to restore safety through repetitive behaviors or mental rituals. These behaviors temporarily reduce anxiety, reinforcing the cycle over time.

For neurodivergent individuals whose nervous systems may already be managing sensory overload, cognitive fatigue, or chronic stress, intrusive thoughts can feel particularly urgent.

The brain is not trying to create suffering.

It is trying to restore a sense of safety and certainty.

Sometimes it just gets stuck.

What Can Help

If intrusive thoughts or compulsive behaviors are interfering with daily life, it can be helpful to speak with a mental health professional familiar with obsessive–compulsive processes.

Evidence-based approaches for OCD often include Exposure and Response Prevention (ERP), a form of cognitive behavioral therapy that helps individuals gradually reduce compulsive behaviors while learning to tolerate uncertainty (Abramowitz et al., 2021).

For neurodivergent individuals, treatment may also benefit from incorporating approaches that address nervous system regulation, sensory needs, and executive functioning challenges.

Understanding how ADHD, autism, and OCD can interact allows clinicians and individuals to build strategies that respect neurodivergent experiences rather than trying to force the brain into a one-size-fits-all model.

Why This Conversation Matters

The intersection between ADHD, autism, and OCD is still being explored in research. However, many clinicians and neurodivergent adults are beginning to recognize that obsessive–compulsive patterns may be more common within neurodivergent populations than previously understood.

Talking about these experiences openly can help reduce confusion and stigma around intrusive thoughts.

For many people, simply learning that intrusive thoughts are a known psychological phenomenon, and that others experience them as well, can bring a surprising sense of relief.

Sometimes understanding what the brain is doing is the first step toward quieting the noise.

References

Abramovitch, A., Dar, R., Mittelman, A., & Schweiger, A. (2015). Comorbidity between attention deficit/hyperactivity disorder and obsessive–compulsive disorder across the lifespan: A systematic review. Harvard Review of Psychiatry, 23(4), 245–262.

Abramowitz, J. S., Taylor, S., & McKay, D. (2021). Obsessive–compulsive disorder. The Lancet, 397(10285), 1426–1438.

Hollander, E., Anagnostou, E., Chaplin, W., et al. (2020). Obsessive–compulsive behaviors in autism spectrum disorders. Psychiatric Clinics of North America, 43(4), 675–688.

Pauls, D. L., Abramovitch, A., Rauch, S. L., & Geller, D. A. (2014). Obsessive–compulsive disorder: An integrative genetic and neurobiological perspective. Nature Reviews Neuroscience, 15(6), 410–424.

Russell, A. J., Mataix-Cols, D., Anson, M., & Murphy, D. G. M. (2005). Obsessions and compulsions in Asperger syndrome and high-functioning autism. British Journal of Psychiatry, 186, 525–528.

van Steensel, F. J. A., Bögels, S. M., & Perrin, S. (2011). Anxiety disorders in children and adolescents with autism spectrum disorders: A meta-analysis. Clinical Child and Family Psychology Review, 14(3), 302–317.

Zandt, F., Prior, M., & Kyrios, M. (2007). Repetitive behaviour in children with high functioning autism and obsessive–compulsive disorder. Journal of Autism and Developmental Disorders, 37, 251–259.