As someone who did blindly reblog the original version of this post, I just want to add on a bit more commentary. All the above has already done a great job of explaining why this is misinformation. I'm going to break down what made the misinformation easy (and appealing!) to swallow, because critical thinking is a great power that I definitely should have used.
The main "stumbling blocks" (so to speak) that can make people fall into believing this right away are:
TikTok user itsdrmax is wearing blue surgical scrubs
Screenshot proves that there is academic work on the subject
Instant hit of validation and/or the sense of "finding an answer" for something
The latter two are simpler to break down, I think. If you see that there is Actual Medical/Scientific Literature on a topic, you're much more likely to think "Ah, then the statement this person is making is correct!" A screenshot of a paper from The National Institutes of Health with an excerpt that corroborates what the man in the video is saying looks like proof. But titles are only titles, and excerpts are only teeny tiny fragments of a summary designed for people to scan quickly when searching the internet. They're not representative of the actual content.
Science is also, er, not an exact science. In order to get any answers at all, a lot of people do a lot of different studies and experiments. Not all of these studies and experiments are equal. Sometimes there are conflicts of interest, sometimes the methodology is flawed, sometimes there are mistakes. The existence of these studies only proves the existence of a theory, which may be disproved or improved upon in the future. This is hard to remember, because we like concrete answers! And it's appealing when someone claims to be able to give us those answers!
But appeal is an emotional reaction, as is that sense of validation. ADHD has been mischaracterised and misunderstood for such a long time, which means the people with ADHD (whether diagnosed, self-diagnosed or undiagnosed) crave that validation from medical/psychiatric quarters, or at least crave explanations for why you work the way you do. You're not stupid or gullible for latching onto something like this; you're just a human being who wants to Know Things about yourself. This is however why it's so important to shore up your critical thinking skills, so you can catch yourself before instantly believing things and then getting disappointed when they turn out to be false/misleading. (And disappointment is by far the best case scenario; misinformation can do serious harm).
All of this is compounded by TikTok user itsdrmax's outfit. The first question: why is he wearing surgical scrubs? He's making a TikTok video; he is not, I would hope, in a sterile surgical environment or on the point or entering or leaving one. There's no practical reason for it, so he must be wearing them for aesthetic purposes. This isn't an inherently bad thing – most people dress up a bit if they're making planned or scripted videos, and a lot of vloggers and vlog-adjacent content creators have signature looks. All it means is that you need to ask yourself what's the purpose of this particular look in this particular context?
The blue surgical scrubs are an instant visual identifier of A Doctor, and he's giving information about a medical matter. On social media, where people are used to scrolling and making split-second decisions about a post based on visual cues and information, having a recognisable look is a powerful tool. This is doubly true when the recognisable look has immediate connotations of trustworthiness. It makes the content seem legitimate, which means people are more likely to interact with it.
I don't know if "Doctor Max" is actually a doctor, and you don't need to find out if he is to question the video's content. People lie online all the time, and if he can buy himself recording equipment, he can buy himself scrubs and stethoscope. If he is a doctor, one has to assume that he's getting his scrubs from other sources, because I doubt any hospital would like their staff taking equipment home to make TikTok videos. Either way, this is a deliberate choice of dress designed specifically to make people think "Oh, this guy is telling me interesting stuff AND I can trust him", thereby garnering more engagement.
You don't need to go further than this. It can be enough to simply ask yourself critical questions about who is making the video to break your fall before it starts. I was curious though, so I decided to look into this guy further, and picked up a few things of note. According to the information on his website, he's a surgeon whose areas of expertise are vascular and visceral surgery. It also says he's authored articles on these topics, which checks out. So, yeah, he is a medical professional – but, he's also making content tailored for social media. In these cases, a solid rule of thumb for any social media content is that engagement and interaction are likely to be at the forefront of the creators' mind, which can negatively impact factual accuracy no matter who the creator is.
What I also found very interesting is that most of this guy's content is just... really, really simple. I don't mean that this is a bad thing, just that there's little to no room for nuance or analysis. The og video of this chain is a great example, actually! He's pretty much paraphrasing the Google search excerpt for the article about postural sway and regional cerebellar volume. And the thing about those excerpts is, they're there to A) get people to click on the website, and B) let people quickly scan results before clicking on the website to learn more. Unfortunately, with Dr Max's snazzy scrubs and his entire online persona as a medical doctor giving people easily accessible information, it sounds like he's telling viewers a concrete fact instead of the results of a single study in an area that needs more research.
(Also, the first thing that comes up on his direct.me is a link to something called Done., which is a website that claims to give therapy to people with ADHD. I don't know how legitimate it is, or what connection there is to Dr Max. I've already spent an hour on this and my dog needs feeding, so I'll save that particular investigation for another day.)