There’s no question that ADHD is a real, biological condition. Research has shown brain differences in people who have ADHD (sometimes called ADD) compared to those who don’t have it. But despite the data, some people still wonder: Is ADHD real?

Here, three people with different ADHD experiences give their answers to that question. One is an ADHD expert and clinical psychologist. Another is a mother of a child with ADHD. The third is a young adult with ADHD.

See how they respond when people question whether ADHD is a “real” condition or say that ADHD is not real.

Thomas E. Brown, Ph.D., adjunct clinical professor of psychiatry and behavioral sciences, Keck School of Medicine, University of Southern California

If someone questions me about whether or not ADHD is real, I first might mention that we have significant scientific evidence that:

1. ADHD is hereditary. I tell them that one out of four people with ADHD has a parent with ADHD. Most of the remaining three have at least one other blood relative with ADHD.

2. There are differences in brain development between kids who have ADHD and kids who don’t. Repeated imaging studies shows that development is similar in almost all areas of the brain. But in specific areas, kids with ADHD are an average of three years behind their peers. These areas are critical for the brain’s management system.

However, my main point is that I know ADHD is real because I have spoken with many hundreds of people who have it. These are children, teens and adults who have suffered criticism over the years. They’ve been told they are lazy because they focus on tasks that interest them, but not on things they “should” be doing. It’s not that they aren’t willing. They just can’t consistently get their brain to do those other tasks.

Amanda Morin, Understood expert and parent of a child with ADHD

Sometimes people ask because they genuinely don’t know and are looking for information. Other times it comes across as more of a criticism or a comment than a question. In those cases, when somebody asks me whether ADHD is real, my first thought usually is, “You do know I have a son and a spouse with ADHD, right?”

But that’s not typically the first thing out of my mouth. Usually, I say lightly, “Really? Come spend a day—no, just dinnertime—at our house and I bet you’d rethink that.” And then I start to think about how well I know the person who said it to me.

If it’s someone who doesn’t know me, I’m much more willing to leave it on that jokey level.

I might also tell them it definitely feels real in our house when we have to get somewhere and I ask my husband to help our son find his sneakers and they both get so distracted that they never make it out the door.

If it’s someone who does know me well, however, it makes me angry when they question whether it’s real. Because then it feels like a comment on my parenting. Or, rather, on my inability to be a parent who can “control” her child.

That’s when I tend to lose my cool and say things like, “Oh, believe me, it’s real. Try listening to your kid cry because his brain is working too fast for him to sleep at night. Or having to make tough decisions about whether or not to try medication. Try talking to your upset child about why he needs to have extra support in school. Then come back and tell me ADHD isn’t real!”

Chloe Gaynor, senior at Emory University and intern at the National Center for Learning Disabilities

Over the years I’ve heard things from other students like, “If I had extra time, I’d do so well on the ACT.” To me, that implies that the people around me don’t understand what it means to have ADHD and doubt that it’s a real thing. Or they think that I don’t have it, and that I don’t need extra support.

Sometimes I’ll take the time to share the struggles I’ve faced academically, and how ADHD affects my life. I tell them that the accommodations don’t help me get ahead—they just help level the playing field. I explain that even with the accommodations I still struggle to finish exams and, just like them, had questions that I didn’t get to answer.

When I relate to them on a personal level and inform them of the challenges I face, it seems to help them to understand it better.

But sometimes I don’t say anything. What’s helped me personally is learning about ADHD myself. I’ve recently spent more time learning as much as I can about ADHD. I’ve read everything from scientific journals to personal stories, and I can say with absolute certainty that—no matter what others think—ADHD is real.