On the surface, obsessive compulsive disorder (OCD) and attention deficit/hyperactivity disorder (ADHD) appear very similar, with impaired attention, memory, or behavioral control. But Prof. Reuven Dar of Tel Aviv University’s School of Psychological Sciences argues that these two neuropsychological disorders have very different roots — and there are enormous consequences if they are mistaken for each other.

Prof. Dar and fellow researcher Dr. Amitai Abramovitch, who completed his PhD under Prof. Dar’s supervision, have determined that despite appearances, OCD and ACHD are far more different than alike. While groups of both OCD and ADHD patients were found to have difficulty controlling their abnormal impulses in a laboratory setting, only the ADHD group had significant problems with these impulses in the real world.

According to Prof. Dar, this shows that while OCD and ADHD may appear similar on a behavioral level, the mechanism behind the two disorders differs greatly. People with ADHD are impulsive risk-takers, rarely reflecting on the consequences of their actions. In contrast, people with OCD are all too concerned with consequences, causing hesitancy, difficulty in decision-making, and the tendency to over-control and over-plan.

Their findings, published in the Journal of Neuropsychology, draw a clear distinction between OCD and ADHD and provide more accurate guidelines for correct diagnosis. Confusing the two threatens successful patient care, warns Prof. Dar, noting that treatment plans for the two disorders can differ dramatically. Ritalin, a psychostimulant commonly prescribed to ADHD patients, can actually exacerbate OCD behaviors, for example. Prescribed to an OCD patient, it will only worsen symptoms.

Separating cause from effect

To determine the relationship between OCD and ADHD, the researchers studied three groups of subjects: 30 diagnosed with OCD, 30 diagnosed with ADHD, and 30 with no psychiatric diagnosis. All subjects were male with a mean age of 30. Comprehensive neuropsychological tests and questionnaires were used to study cognitive functions that control memory, attention, and problem-solving, as well as those that inhibit the arbitrary impulses that OCD and ADHD patients seem to have difficulty controlling.

As Prof. Dar and Dr. Abramovitch predicted, both the OCD and ADHD groups performed less than a comparison group in terms of memory, reaction time, attention and other cognitive tests. Both groups were also found to have abnormalities in their ability to inhibit or control impulses, but in very different ways. In real-world situations, the ADHD group had far more difficulty controlling their impulses, while the OCD group was better able to control these impulses than even the control group.

When people with OCD describe themselves as being impulsive, this is a subjective description and can mean that they haven’t planned to the usual high degree, explains Prof. Dar.

Offering the right treatment

It’s understandable why OCD symptoms can be mistaken for ADHD, Prof. Dar says. For example, a student in a classroom could be inattentive and restless, and assumed to have ADHD. In reality, the student could be distracted by obsessive thoughts or acting out compulsive behaviors that look like fidgeting.

“It’s more likely that a young student will be diagnosed with ADHD instead of OCD because teachers see so many people with attention problems and not many with OCD. If you don’t look carefully enough, you could make a mistake,” cautions Prof. Dar. Currently, 5.2 million children in the US between the ages of 3 and 17 are diagnosed with ADHD, according to the Centers for Disease Control and Prevention, making it one of the most commonly diagnosed neuro-developmental disorders in children.

The correct diagnosis is crucial for the well-being and future trajectory of the patient, not just for the choice of medication, but also for psychological and behavioral treatment, and awareness and education for families and teachers.

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