ADHD’s High Heritability and Prevalence Rates

Most people do not realize that ADHD is so highly heritable and prevalent in families. Heritability rate is a measure of what percentage of symptoms are directly due to genetic factors versus environmental factors, which is typically determined by studying twins. Some studies have suggested as high as a 90% heritability rate for ADHD. Prevalence rates refer to the odds of a condition occurring in a population. Prevalence rates for a child having ADHD when one parent has it are estimated to be around a 57% prevalence rate in a family.

As part of my screening of new client’s on the phone, I always ask if ADHD has been diagnosed somewhere in the family. If so, then ADHD evaluation should be highly considered for that individual. It is common for me to diagnosis one family member, and then to have others follow behind them. What is intriguing is how differently each individual in a family presents ADHD symptoms.

Online you can search countless “types” or “subtypes” of ADHD. The most common characterization is of Inattentive, Hyperactive/Impulsive, and Combined types; which is in line with how ADHD is currently diagnosed via DSM-V criteria. All of these “types” are somewhat misleading though. They are simplified categories of symptoms that do not account for how individuals compensate for their symptoms. This becomes important when seeking evaluation for ADHD as primary ADHD symptoms are often concealed by the layers of compensation strategies that individuals develop over a lifetime to improve their functioning, socially mask their problems from others, and to reduce the fallout from their chronic executive functioning difficulties. This is why so many females, adults, and intelligent individuals are not diagnosed till later in life, if ever.

More so than many other medical and/or mental health diagnoses, ADHD really presents uniquely through one’s personality. How social they are? How they engage others? How they manage emotions? How they make decisions? What is motivating to them? What are their baseline cognitive capacities? How do they compensate?

Evaluation for ADHD requires ruling out possible causes of reported symptoms such as anxiety, depression, trauma symptoms, head injuries, learning disabilities, etc. And then if ADHD is identified as the primary cause of reported symptoms it is important to determine what are secondary issues that trail behind ADHD. Is that anxiety disorder they thought they had independent from ADHD? Was presumed Dyslexia actually the cause of reading difficulties? Was Bipolar Disorder the cause of emotional dysregulation? It is fairly common for me to see and hear that peoples’ story for their lifetime of symptoms and difficulties changes when ADHD is finally identified. This can be an extremely powerful and meaningful experience for them. And often the story for an entire family ends up changing as well.

What is interesting to me as someone who specializes in evaluating for ADHD is that as high as ADHD heritability rates are (upwards of 90%) and as high as prevalence rates are in families (approximately 57%), we know that those studies are largely based on the current diagnostic criteria that prioritizes diagnosis of 5-8 year old males. The classic stereotype of what hyperactive/impulsive ADHD looks like. How high will heritability and prevalence rates actually rise as we begin to understand just how much it runs in families when we account for those who do not present in a stereotypical fashion (i.e., females, more inattentive presentations, adults, those signficantly over-compensating for symptoms, and intelligent individuals).