OCD and ADHD: Why the overlap? (with poll)

I recently saw a clever t-shirt logo that read “It’s not that I have ADHD it’s just that… Oh look a squirrel!”

You may ask, what does that have to do with OCD?

Well, that t-shirt made me think back and realize that over the past year, a very large proportion of the patients who came to me for CBT treatment of OCD also either have a diagnosis of ADHD or I strongly suspected that they would meet the diagnostic criteria for ADHD. (In studies of adolescents with OCD the overlap has been found to be as high as 1 in 4).

By way of comparison, when I first started seeing OCD patients thirty years ago, I rarely saw patients with ADHD in addition to their OCD. Why the change?

One reason is that ADHD in adults being diagnosed far more frequently as clinician ask their patients screening questions that can signal ADHD

The most useful screening questions, developed by my colleague Tom Spencer and others, and used worldwide by the World Health Organization include these:

    • How often do you have trouble wrapping up the final details of a project,
      once the challenging parts have been done?
    • How often do you have difficulty getting things in order when you have to do
      a task that requires organization?
    • How often do you have problems remembering appointments or obligations?
    • When you have a task that requires a lot of thought, how often do you avoid
      or delay getting started?
    • How often do you fidget or squirm with your hands or feet when you have
      to sit down for a long time?
    • How often do you feel overly active and compelled to do things, like you
      were driven by a motor?


See the  full screening scale here

But another reason is that I have also become far more observant of the overlap in symptoms between these two disorders. In some cases, I could make an argument that the same symptom could be an indication of OCD or the equal argument that the symptom could be a sign of ADHD.

For example the symptoms below are commonly found in both OCD and ADHD:

  • Perfectionism
  • Procrastination
  • Hoarding
  • Distracting thoughts/obsessions

Then there is the recognition that both OCD and ADHD affect the same general area in our brains.  For example, in the latest revision of my book, Getting Control, I wrote that:

The most commonly accepted theory of OCD involves overactivity in a brain circuit connecting the orbital-frontal cortex, the striatum, and the thalamus (often called simply the “CSTC” circuit, which connects the control centers of the more recently evolved orbital-frontal cortex – “orbital” because it lies above the orbits of the eyes, “frontal” because it is at the front of the brain – with more ancient areas deeper in the brain that control movement).

Well it turns out that both OCD and ADHD appear to share abnormalities in the same areas of the human brain.  In fact, if you change the word “overactivity” to “underactivity” in the quote above, you will have a pretty good understanding of the current theory of ADHD.  So the general brain areas involved are the same, but the underlying physiological processes may be different.
Further, on very specialized tests of memory and other cognitive tasks called a neuropsychological battery of tests, the pattern of results are very similar between patients with OCD and those with ADHD, and both show similar deficits compared to subjects with no psychological condition:

  • problems in planning
  • problems in organization
  • problems in controlling impulses

See a summary of a recent paper by my MGH colleague Dr. Amatai describing these similarities here

In future posts, I will discuss the similarities and differences in the CBT treatment of OCD and ADHD.  In the meantime I would like you to share your experiences if your loved one suffers with both signs of OCD and ADHD.

Does your loved one have symptoms of both OCD and ADHD?

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