By Stephanie Sarkis, Ph.D.
Many people ask me what the difference is between attention deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD). Both ADHD and OCD seem to be highly heritable: if you have it, it’s likely that at least one of your parents also has it. When you have ADHD, one of the issues is that your brain has a low level of a chemical called dopamine. When you have OCD, one of the issues is that your brain has too much of a chemical called serotonin. Sometimes people have both ADHD and OCD. This means that you have the inattention and/or hyperactivity of ADHD, along with the compulsions and/or obsessions of OCD.
Sometimes people with ADHD tend to have what look like compulsive tendencies. This is because we’ve learned to overcompensate for difficulties that we’ve experienced with distraction, disorganization and inattention. For example, when I shut the trunk of my car, I look to make sure my keys are in my hand. I also check that the stove is turned off after I’ve been using it and about to leave the house. I don’t do those things because I have a compulsion; I have tendency to misplace my keys, so I want to make sure that I know that they’re with me and in my hand before I shut the trunk of the car, and I check the oven because I’ve left it on before when I was at home. So there are some things that people with ADHD do to compensate for having problems with attention, focusing and forgetfulness.