ADHD or OCD? How Clinicians Tell Them Apart

Written by the practice's editorial team. Published October 19, 2026; updated October 19, 2026. Part of the Adult ADHD Symptoms Guide, is it adhd? section. Medically reviewed by John C. Shershow, M.D. on October 19, 2026. Editorial policy

Key points

NIMH describes OCD as uncontrollable, recurring thoughts (obsessions), repetitive behaviors (compulsions), or both, and says people with OCD generally spend more than 1 hour a day on them.
ADHD in adults requires several symptoms that began before age 12, at least five current symptoms in one area, and impairment in at least two areas of life, according to NIMH.
NIMH says OCD usually starts between late childhood and young adulthood, and that an estimated 1.2% of U.S. adults had OCD in the past year.
A 2015 Harvard Review of Psychiatry review found reported ADHD-OCD co-occurrence rates highly inconsistent and warned that ADHD-like symptoms caused by OCD may be misdiagnosed as ADHD.
In a 2012 study comparing 30 adults with OCD, 30 with ADHD and 30 healthy controls, both clinical groups scored lower on thinking tests, but only the ADHD group reported high impulsivity.

Losing your train of thought, rereading the same paragraph, running late because you got stuck on something: adults with ADHD describe these problems, and so do adults with obsessive-compulsive disorder (OCD). From the outside the result can look the same. The cause underneath is usually very different, and so is the treatment. This page explains how clinicians separate the two, how often they occur together, and what to bring up at an evaluation.

What each condition is

The National Institute of Mental Health (NIMH) describes ADHD as a persistent pattern of inattention and/or hyperactivity and impulsivity that makes it hard to function in at least two areas of life, such as home, school or work. Symptoms must begin before age 12. Adults (over age 16) need at least five symptoms of inattention or of hyperactivity-impulsivity, and the symptoms must last at least six months. The adult ADHD symptoms overview covers the full picture.

NIMH describes OCD as a long-lasting disorder in which a person has uncontrollable, recurring thoughts (obsessions), engages in repetitive behaviors (compulsions), or both. Obsessions are repeated thoughts, urges or mental images that are intrusive and unwanted. Compulsions are repetitive behaviors a person feels the urge to do, often in response to an obsession, such as checking that the door is locked or the oven is off, cleaning, ordering items, counting, or silently repeating words.

NIMH also notes that everyone double-checks things sometimes. People with OCD generally cannot control their obsessions or compulsions even when they know they are excessive, spend more than an hour a day on them, get no pleasure from the compulsions (though they may feel brief relief from anxiety), and have significant problems in daily life as a result.

Where the two look alike

Trouble concentrating. In ADHD, attention drifts to whatever is more interesting or nearby. In OCD, attention is captured by intrusive thoughts or by the urge to complete a ritual.
Slowness and unfinished tasks. Both can make work take far longer than it should. In OCD, time can be lost to checking, redoing or getting something to feel "right."
Forgetting and losing things. Forgetfulness and losing things are listed ADHD symptoms. NIMH lists fear of forgetting, losing or misplacing something as a common OCD obsession, which can lead to repeated checking.
Weaker scores on thinking tests. A 2012 study in the Journal of Neuropsychology compared 30 adults with OCD, 30 with ADHD and 30 healthy controls. Both clinical groups performed worse than controls across the neuropsychological domains tested.

The key differences

Feature	ADHD	OCD
Usual start	Several symptoms before age 12 (required for diagnosis)	Usually between late childhood and young adulthood; most people are diagnosed as young adults
Why attention slips	Inattention: difficulty paying attention, staying on task or being organized	Attention is taken up by intrusive, unwanted thoughts and the urge to perform compulsions
Relation to anxiety	Not part of the diagnostic definition	Obsessions typically cause anxiety; compulsions bring temporary relief
Impulsivity	A core feature in hyperactive-impulsive and combined presentations	In the 2012 comparison study, adults with OCD did not differ from healthy controls on behavioral impulsivity
Repetition and checking	Not characteristic; the problem is more often skipping steps or forgetting	Characteristic: repeated checking, ordering, counting or cleaning, often more than an hour a day
Course	Continuous pattern; NIMH says inattention tends to persist with age while hyperactivity tends to decline	Symptoms may start slowly, ease for a while, and often worsen during stress
Common first-line treatments	Medication (usually stimulants) and behavioral or cognitive behavioral therapy	Cognitive behavioral therapy, especially exposure and response prevention, and antidepressants that target serotonin

The ADHD rows come from NIMH's adult ADHD publication and the OCD rows from NIMH's OCD publication, except the impulsivity row, which comes from the 2012 comparison study listed in the sources.

Why OCD can be mistaken for ADHD

A 2015 systematic review in the Harvard Review of Psychiatry, led by researchers at Massachusetts General Hospital and Harvard Medical School, examined two decades of studies on ADHD and OCD together. The authors found that reported co-occurrence rates were highly inconsistent and that many studies had methodological problems, including possible clinical misinterpretation of symptoms. They encouraged clinicians to consider that ADHD-like symptoms resulting from OCD may be misdiagnosed as ADHD.

The 2012 study by the same research group offered one explanation, which the authors called an "executive overload" model: constant attempts to control obsessive thoughts may overload the brain's executive system, so attention and planning suffer as a side effect of OCD rather than as a separate attention disorder. This is a proposed model, not a settled fact, but it explains why a person with OCD can look distractible.

Another reason OCD can be missed: NIMH notes that people with OCD may not tell their health care provider about their obsessions and compulsions out of fear of judgment. If a clinician only hears "I can't focus," ADHD may seem like the obvious answer.

Can you have both?

Yes, though how often is debated. A 2014 review in ADHD Attention Deficit and Hyperactivity Disorders described high comorbidity between the two, especially ADHD in children with OCD, and reported that partly similar executive functions are affected in both. The 2015 Harvard review, however, found genetic support for true co-occurrence only in children and noted lower reported rates in adolescents and adults. It also found that tic disorders may inflate the rates; NIMH notes that some people with OCD also have a tic disorder.

The practical takeaway: having one diagnosis does not rule out the other, and an adult with both deserves a careful look at which symptoms belong to which condition. The companion page ADHD and OCD together covers that situation in more detail.

Why the distinction matters for treatment

The treatments differ. NIMH lists stimulant medication and behavioral or cognitive behavioral therapy as the most common ADHD treatments. For OCD, NIMH describes exposure and response prevention, a specific type of cognitive behavioral therapy, and antidepressants that target serotonin. A treatment aimed at one condition is not designed to relieve the other, which is why getting the diagnosis right comes first. Anxiety more broadly is covered on the ADHD or anxiety page.

Questions an evaluator may ask

When you lose focus, where does your attention go: to something more interesting, or to a worry you cannot shake?
Do you repeat actions (checking, rereading, rewriting) until they feel "right"? How much time does that take each day?
Does doing the ritual lower your anxiety for a while?
What were you like in elementary school: restless, forgetful, daydreaming? Or did the problems begin later?
Have you or anyone in your family had tics?
Do the problems show up at home, at work and in social life, or mainly around certain fears?

NICE guidance for ADHD says diagnosis should rest on a full clinical and psychosocial assessment, including a developmental and psychiatric history, and should not rest on rating scales alone. It also calls for assessing coexisting conditions. Dr. Shershow's adult ADHD evaluation follows that logic: it covers current symptoms, childhood and work history, health and substances, and other explanations such as anxiety that may account for symptoms or occur alongside ADHD. The evaluation page describes the process, and how to prepare for an evaluation lists what to bring. If the answer turns out to be something other than ADHD, what if it's not ADHD explains next steps.

When to talk to a clinician

Consider an evaluation if focus problems, repeated checking or intrusive thoughts take up real time, cause distress, or keep getting in the way at work or at home. You do not need to know which condition it is before you ask. The adult ADHD self-test can help you organize what you notice, though it cannot diagnose ADHD or OCD. For adults in New York or New Jersey, ADHD testing in NYC and ADHD testing in New Jersey explain how an evaluation with Dr. Shershow works. If you are in crisis, call or text 988 at any hour.

Questions

Can OCD look like ADHD?

Yes. A 2015 systematic review warned that ADHD-like symptoms caused by OCD may be misdiagnosed as ADHD. Intrusive thoughts and time-consuming rituals can make a person seem distracted and slow, even when the underlying problem is OCD.

Can ADHD and OCD occur in the same person?

Yes, although estimates of how often vary widely. A 2014 review described high comorbidity, especially in children, while a 2015 review found reported rates inconsistent and lower in adults. Each condition is diagnosed on its own criteria.

Is double-checking things a sign of ADHD or OCD?

Repeated checking to relieve anxiety is a common OCD compulsion, according to NIMH. Everyone double-checks sometimes. NIMH says people with OCD generally cannot control it, spend more than an hour a day on obsessions or compulsions, and have real problems in daily life as a result.

Does OCD start in childhood like ADHD?

It can, but NIMH says OCD symptoms usually start between late childhood and young adulthood and most people are diagnosed as young adults. ADHD diagnosis requires several symptoms before age 12.

Does Dr. Shershow treat OCD?

Dr. Shershow focuses on adult ADHD. His evaluation considers other explanations for symptoms, including anxiety-related conditions, and explains what it found and which options fit. Call the office to ask how a specific situation would be handled.

Sources

This article is general information, not medical or legal advice. Rules and coverage change; check the linked sources for the current position, and speak with a clinician or attorney about your own situation.

ADHD or OCD? How clinicians tell them apart