Hello, how's it going? We have another podcast for you today. Unfortunately, it's the rhetorical we. My wonderful co-host, Dr. Fu, is not here today. But moving forward, he will be on all the other casts today. He just couldn't make it today. So yeah, today talking about ADHD, I'm going to talk about, you know, start with the DSM, talk about some of the problems with it, going to talk about how ADHD is diagnosed and some of the problems with that, going to be talking about what the underlying thing that's wrong with ADHD, you know, kind of get at the core of what's kind of going on.
Then going to get to the juicy stuff. Is ADHD real? Why I think that question comes up a lot, if I think it's real. Going to talk a little bit about the history of ADHD, how we got to the diagnosis that it is today, and how that can usually inform us as to why it's thought of the way it's thought of. I'm going to help people work through the thought, you know, if you ever had thought, do I have ADHD?
You know, who hasn't had that thought? I'm going to talk about what it means to have ADHD and what I think is the best way to think about it if you do have ADHD. I'm going to cover questions like, is it biological or developmental nature versus nurture? Right now, it sounds like this is going to be organized, but realistically, I'm just going to be doing a lot of rambling and we'll see how it goes.
And then just a disclaimer, I am not an expert on ADHD. I am a clinician. What that means is that I haven't read every single ADHD paper. I'm going to have gaps in my knowledge. What I say is not the be all end all correct answer to things. So everything I say is going to be heavily infused with my biases, with my blind spots. Whenever you're talking about a topic like this, you can't go to one source to get your information.
You really need to hear different perspectives and then piece together what your view is. So let's get started. First, we're going to start with the DSM. So we kind of touched on it a little bit in the last podcast. The DSM is looking at outputs. The DSM is looking at behaviors. It looks at things that are observable. And the big issue with that is that it's relatively agnostic as to what's going on underneath.
So the benefit is that it's more objective because you're looking at observable qualities. But this comes at a cost. So the big cost is when you're looking at behaviors or outputs, you're going to get a group of heterogeneous people. All these people are going to have different problems. They're not going to be a unitary group that is all the same. So I guess let me talk about the criteria first.
So it's a persistent pattern of inattention and hyperactivity impulsivity. that interferes with functioning or development characterized by one, inattention, or two, hyperactivity. So for the inattention subtype, it's gotta have greater or equal to five symptoms of A, lack of attention to details, B, difficulty sustaining attention, C, does not seem to listen when spoken to directly. D, does not follow through on instructions. E, difficulty organizing tasks. F, avoids tasks that require sustained mental effort.
G, loses or misplaces objects. H, easily distracted. Or I, forgetful in daily activities. for the hyperactivity and impulsivity category we're looking at a fidgetiness b leaves their seat frequently c feeling restless d unable to engage in leisure activities quietly e always on the go f talks excessively g blurts out answers h difficulty waiting turn i interrupts or intrudes others and then the other criteria i might have mentioned a few of them Symptoms have to be present before the age of 12.
It must be present in two or more settings. It must reduce the quality of functioning, and it doesn't occur due to a psychotic disorder or better explained by another mental disorder such as a mood, anxiety, dissociative personality, or substance use disorder. So there's three subtypes. You can have inattentive subtype where you fit the inattention symptoms. You can have the hyperactive subtype where you fit the hyperactive symptoms or the combined type where you match onto both.
So as I mentioned before, the DSM is looking at these behavioral issues. It's looking at these things that can be observed. And the issue is that because of that, it's going to cast a wide net and you're going to see a lot of differences in that group. You're going to see people that are super low functioning. You're going to see people that are super high functioning. There's not a universal underlying mechanism here because we're looking at the observable behavior.
We're not looking under the hood as to what the problem is. I think I used a similar analogy in the last podcast. This isn't like strep throat where I can do a culture and it'll come back and it'll say streptococcal infection and then I know that the throat pain is the result of this specific problem. For ADHD, the analogy for throat pain was we're saying you have this throat pain but we're not specifying if it's an infection, we're not specifying what infection it is.
We're not saying if it might be allergies, it might be GERD, it might be an overuse injury. We're not specifying what the underlying thing is. We're kind of just describing the behaviors that we see. So I'm just clarifying that that's how the DSM approaches it. The DSM is what we call agnostic as to the etiology of what's going on. But now I'm gonna move on and talk about how I view what the underlying thing is that's wrong with ADHD.
So what the ADHD diagnosis is trying to capture is it's trying to capture people who have deficits in executive functioning. now one thing to make a little bit more complicated executive functioning is a pretty big term it refers to a set of cognitive processes that allow the individual to manage and regulate their thoughts actions and emotions to achieve goals and to adapt to changing environments some key components of executive functioning here we're thinking of working memory this is the ability to hold and manipulate information in your mind it's like the ram on the computer We're talking about cognitive flexibility, so the capacity to shift your thinking or adapt your behavior.
We're talking about inhibitory control, so the ability to suppress inappropriate responses or resist distractions. We're talking about planning and organization. We're talking about task shifting, task initiation, and self-inhibition, emotional regulation. It covers a lot of broad, general cognitive functions. So if you were to rank everyone's executive functioning, it'll come up like a normal curve. This is like your bell-shaped curve picture, the kind of curve if you were to map height.
So this is a symmetrical curve. The mean, median, and mode are all perfectly in the middle. One standard deviation will capture 68%, two standard deviations, 95%. If that doesn't mean anything to you, don't worry about it, but just picture a curve that's a hill and perfectly symmetrical. So what ADHD is capturing is people in the super duper low percentile of executive functioning. So that means that we're looking at people who are really on the low percentile of executive functioning.
So what that means is it's a spectrum. It's not a categorical thing. It's not a problem that you have or you don't have. And that also means that the cutoff will be relatively arbitrary. When I look at prevalence numbers for adult ADHD, I usually see about 4%-ish. For childhood ADHD, I see 5% to 10%-ish. But these numbers are increasing. Looking at childhood ADHD in 1997, it was like 6%.
In 2017, it was like 9-ish percent. In 2021, it was like 11%. So ADHD, what we're supposed to be looking at is executive functioning that's such a low percentile that it's impairing the person's functioning, that it's acting as a bottleneck for the person to function. And what we see is that the cutoff is really moving to the right. There are people who are pro-ADHD who argue that it's moving to the right, that the percentage of people diagnosed is increasing because we have better screening, we have better access, and that we understand the disorder.
So that's the optimistic view. The less optimistic view will point out that the diagnosis is really based on subjective reporting. And, you know, yes, we are looking at strict DSM criteria. But the problem is the criteria, it's not concrete. You know, it needs to meet the criteria that it's impacting function. That's a really vague idea. thing that every clinician, every provider is going to have a different definition and a different calibration for what they view as affecting functioning.
And to me, it is worrisome that we see this creep of what percentile of executive dysfunction that we're counting as part of the disorder. So when you look at something, you know, if we have a prevalence of about 4%, that's relatively close to two standard deviations below the mean. To me, that's reasonable. And I think it's noticeable to the average person that more and more people are being diagnosed with ADHD.
So this is why the question of, you know, is it a real diagnosis or not? This is why the average person is asking that question. When you ask, is it real? To me, the question doesn't make a lot of sense because to me, of course, people who are in the bottom tier, few percentile of executive functioning, that it's going to cause massive problems in their life. And it's going to be a major bottleneck for them to function, for them to have successful relationships, for them to have success at work.
To me, of course, that is a real thing. But I think the thing that people are picking up on and are questioning is that the cutoff for what we define as the disorder is relatively arbitrary, that it's not a number that is set in stone. And I think a thing that bothers people is if we call something a disorder or a disability, then inherently that person deserves accommodations.
And another thing is that we naturally will interpret the behavior of someone with a disability in a different light than someone who doesn't have a disability. And this is appropriate. This is good. So I think the thing that bothers the average person, whether or not they're able to articulate it in the way I'm going to, is that as we see the percentile creep, So if it starts out at 2% of the population is diagnosed, we're looking at people with major dysfunction in their executive functioning that accommodations will change their lives.
If we see it creep to 6%, to 8%, to 10%, to 15%, does the person who's in the 15th percentile warrant being called a disorder or warrant being called a disease? Does it warrant getting special accommodations? The answer is gonna be less clear. And then I guess another thing that I should have mentioned earlier, the optimistic people are saying that the number of ADHD diagnoses are increasing because of better screening, because of better access to treatment, because we understand the disorder better.
But then the flip side is that it also is increasing as a result of people who financially benefit from spreading the diagnosis. And I'll just provide one example just so that you can understand that there are social factors that influence how many people are diagnosed. So there was a law called the Ryan Height Act. I don't know a ton about the law, but it made it so that you had to see a person in person in order to prescribe controlled substances.
And the purpose of the law was to regulate online internet prescriptions, and it's enforced by the DEA. When COVID happened, they loosened up on this law, and it allowed people to prescribe controlled substances through telemedicine. And what we saw was just an absolute explosion in regards to stimulant prescriptions. So what I'm saying is these companies were financially incentivized to diagnose these people with ADHD and had very, very, very loose prescription practices.
But let's not get caught in the weeds. The point of this is ADHD, in terms of what it should be representing, is the extreme lower end of a continuous dimensional trait of executive functioning. So it's hard to go into the exact problems that are occurring because it's such a label with a pretty broad range. And there is no pathognomonic neuropsychological profile for this disorder. The thing that I see come up the most is dysfunction in the form of impaired response inhibition.
That's probably one of the more prominent cognitive aspects of ADHD. So response inhibition would be the suppression of action, behavior, or cognition that is inappropriate for a given task. So if you're going to be deficient in motor inhibition, you're going to come off as restless and hyperactive because you can't tell your brain to stop the behavior. If you have impaired verbal inhibition, you're going to be talking excessively you're going to be interrupting you're not going to be listening as well if you have if you're deficient in cognitive inhibition you're going to have difficulty suppressing thoughts that are not relevant to the task that you're doing So let's say you're sitting down and you want to do your taxes.
The typical person will be able to suppress thoughts that are not relevant to doing their taxes. If they see some salient thing going on outside, they're able to say, that's not relevant to me right now. Let me ignore that. So people with ADHD have difficulty inhibiting or suppressing external things that are not relevant to the task at hand. And if you struggle with inhibition, you're going to see it impact other neuropsychological cognitive abilities.
Another one of the core deficits, especially in the inattentive type, is difficulty with sustained attention. So that's the ability to maintain consistent focus, to have continuous activity. And as these systems are interconnected, a huge part of sustained attention is ignoring all the other stimuli that are not pertinent to the thing that's currently going on. A common thing you'll hear is someone will say, this person doesn't have ADHD because they can focus for five hours on video games.
Or, you know, if someone's really into car work, you know, they can sit there for four hours at a time and work on their car. Now, some people conceptualize ADHD as like a motivational deficit disorder. So there's difficulty in motivating and doing things that aren't inherently rewarding. So there are a million times throughout the day that a person experiences a decision if they want to do something now or later.
So if the thought of a donut pops into my head, You know, ooh, should I eat this donut now or should I think long term? Someone with ADHD won't be able to suppress that thought, put it aside, and it makes it so that they're kind of selecting for things that are inherently rewarding and for things they want now. So that's why someone with ADHD can focus at a longer length of time on something that they're very interested in because they find that activity inherently rewarding.
So something like video games, which provides a ton of little rewards, as you're playing, the person won't need to rely on executive functioning. They won't have to suppress external thoughts because this activity in itself is rewarding for the individual. So it's not correct to view ADHD as the person is unable to pay attention to things. Rather, their attentional system is disrupted in a way that they can't suppress external things.
so that when things aren't inherently rewarding, they have a ton of difficulty paying attention. So someone with ADHD, it's not impossible to pay attention. It just requires a lot more mental effort to pay attention to things that the person doesn't find stimulating or rewarding. Now, a totally separate way that I've heard, but interconnected way I've heard ADHD, one of the core deficits associated with ADHD formulated has to do with the default mode network and the task positive network.
So I think it sounds more complicated than it is. These are two large-scale brain networks that are associated with different types of cognitive activity and they typically function in opposition to one another and they're involved in different mental states. So the default mode network is the network that's on in your brain when you're at rest and you're not focused on really anything specific. So when you're not really doing anything, the network that's on is daydreaming.
It has a lot to do with autobiographical memory. So you're thinking pretty vague sense about past experiences and projecting them onto the future. and typically you're you're reflecting on other people's thoughts and feelings um you're thinking about yourself your own emotions so it's the default mode network that's acting primarily when you're at rest when you're kind of just sitting there this is in contrast to the task positive network this is turned online whenever you're paying attention to something whenever you're trying to problem solve whenever you're kind of involved in a task And this is really the network that makes you goal-oriented.
So it suppresses other impulses. You're not gonna wanna scratch your nose when you're deep in a task. You're not gonna be thinking about the thing that's outside your window when you're deep in a task. So for the average person without ADHD, If one of these networks is active, the other one is not active. So it's kind of like a seesaw. So if you're really engaged in a task, then you have the task positive network fully activated and the default mode network is kind of shut off.
And then when you flip it, if you're at rest and you're not focused on a task, then the default mode network is completely activated and the task positive network is not really running. So what researchers have suggested is that one of the reasons people with ADHD struggle is because their default mode network does not go offline when their task positive network kicks in. So you're trying to complete this task and trying to work on this task, but your default mode network is still kind of there, wondering about the thing that the person said to you this morning, thinking about the slight that you had from your friend the other day, worried about the future and the vacation that's planned.
Whereas when someone doesn't have ADHD, they're not intruded on by all these default mode network type thoughts. Now, this isn't an inherently bad thing. People with ADHD tend to be really creative out of the box thinkers. And that's probably the result of the fact that their brains are functioning slightly differently. So on one hand, it helps you to think differently, to think creatively, to think out of the box.
But on the other hand, it can make everyday mundane tasks that need to be done very difficult. And I like this formulation. I also like the idea that there's things that you can do to make sure you better engage your task positive network. You know, different forms of breathing, meditation, physical exercise. These are all things that better engage your task positive network. So it's things that you can work on if you have ADHD.
All right, so now I want to talk about is ADHD biological? Is it a disease? Is it a disorder? Yeah, I kind of want to address a few of these questions. So there's a lot of people who have a lot of stock in the idea that this is a biological disorder. And I think some of these people are acting in bad faith because when they say it's a biological disorder, what they're actually saying is that this is something that's wrong with me, that I have no control over.
that I'm not responsible for the mistakes I make. There's some ulterior motive to the idea behind whether or not it's biological. And I have to admit, I am bothered by the idea that we're telling more and more kids that they have a disorder, that there's something wrong with their brain. That inherently gives me the heebie-jeebies. I think that there's a ton of damage that can be done by telling a kid or telling yourself that I have a brain that doesn't work, it's dysfunctional, I have a disorder, I don't make certain chemicals that other people make.
And I think that there will be a self-fulfilling prophecy that will take place. If I think of myself as someone with an inherently broken brain, it's going to impact my self-esteem. It's going to impact whether or not I take on certain tasks. It's going to give me a question whether or not I can handle certain things. And then I should point out that I don't think someone with ADHD has a broken brain.
I don't think that they're incapable of synthesizing certain chemicals. I'm just saying that there is a problem with calling something a disorder and saying it's biological and neurological and a child who can't understand all the nuance will hear a lot of those words and just think something's wrong with me. And now the flip side, why is it also problematic if we don't have words to discuss something like ADHD?
So when I talk to people, adults that I see have ADHD and were never diagnosed, it's so common to see a history of being criticized when they were children because they weren't listening. They have a history of being yelled at by teachers, by parents. by people who said they were lazy, that they weren't listening. They have a history of severely underperforming in school. You'll hear things, I wanted to go into medicine, but it was too hard for me, so I switched majors.
A lot of people with undiagnosed adult ADHD have a lot of self-esteem issues as a result of feeling bad because they were told that they were a bad kid when they weren't able to fit in. So in a sense, we're dealing with two separate problems. If we call this thing a disorder and we tell people that they have a dysfunctional neurocircuitry, dysfunctional biochemical issues, I think that's going to reflect relatively negatively on their long-term self-esteem.
On the flip side, if we don't have a language... and an understanding as to how these things can impact a child and an adult's functioning then there are a lot of people who will develop a poor sense of self-esteem they'll think a lot of negative thoughts about themselves that aren't appropriate and are the result of difficulties in executive functioning not that they are a morally bad person So I think if I could – we can't change the paradigm of the fact that the disorder is called ADHD and that the language we use for people who have those symptoms is whether or not you have ADHD.
I think we should move to a paradigm – so I don't think it's possible for me to overthrow that entire infrastructure that's occurred around that. But I think it can be helpful for people to think, you know, rather than wonder if I do or don't have ADHD, you know, whether my partner does or doesn't have ADHD. Recognize that, again, we're talking about a continuous trait and that for a lot of people, they're going to have ADHD symptoms that are going to impact them.
So I think it'll be helpful to remove the idea that there's two categories of people with ADHD and people without ADHD. and that people with ADHD have broken brains, that they have dysfunctional neurocircuitry. And I think it can help you to understand that there's people across the whole spectrum and that we don't need to introduce the words like dysfunction and disorder to understand those people. And I think by removing the idea that it is biological, that it's binary, We can also understand how much the environment plays a role here.
So we know people who aren't the best at executive functioning. One of their core problems is that they have a difficulty focusing on something if there are other salient things going on in the environment. But if there's a thing that is highly salient that's very inherently rewarding, then even someone with executive dysfunction will be able to focus on it. Well, we see that whether consciously or unconsciously, our culture has picked up on this.
And that's why we see things sold to kids that are super bright colors. They're super salient. We see food that is really high in simple sugars that is really rewarding. We see apps that are developed entirely with an algorithm that is meant to be as addictive as possible, to have these perfect ratios so that our brains get completely absorbed and addicted to them. So we see our food, we see our television, the things we're consuming, movies, products, everything is being made to be as salient as possible.
We see things hyper-sexualized, hyper-sugarized, People have recognized that there's money to be made by making things as inherently rewarding as possible. So this is a problem for people who aren't able to focus on things that are not inherently rewarding. because they're being bombarded with all these other options that are so inherently rewarding. So there is a cultural shift that we see that there are more things that are super distracting.
And as a result, people with executive function problems are gonna have more and more problems. And that bell curve, it actually makes sense that it's moving to the right because now the things that are competing for people's attention, it's things that are super duper exciting and rewarding. So what's my point there? I kind of forget. I think what I'm trying to say is don't get caught into the simplicity trap that either you have a biological problem that you have no control over or you're a normal person.
And also, I think it's important that you don't think that ADHD is this disease or disorder that exists independently of the cultural, sociological, and psychological environment of the individual. And I think that's an important point because there's like a fatalistic trap that you can fall into if you think of it as too biological. And you have to recognize that there are, you still have so much control over how well you function, even if you have ADHD or ADHD traits.
and and for the people who have you know one foot in the idea they have adhd and one foot outside of it i i hope that you can better understand yourself by thinking of yourself as someone with some adhd traits and i you know some people kind of get locked into the idea you know if it's biological then therefore i need stimulants Or if it's biological, then the only treatment is stimulants.
And on the flip side, if it's not biological, then it doesn't need stimulants. And this distinction is not something that changes treatment. And to summarize how I think of treatment, I think stimulants are going to improve your executive functioning, whether or not no matter where you fit on the bell curve, and that there are psychological tools and environmental changes that you can make that will decrease the symptoms you experience, again, no matter where you are on the bell curve.
And this brings me to a bit of a different point that I see there's a huge variance as to how people internalize, how they make sense of their disorders, how they integrate the possibility that they have a disorder into their identity. And I think that there are healthy ways of understanding your diagnosis and that there are unhealthy ways of understanding your diagnosis. And I think a large part of this boils down to if you have an internal locus of control or an external locus of control.
So if someone has an internal locus of control and they're given the diagnosis of ADHD, then what they're going to say is, I need to do certain things in order to manage the symptoms of this disorder. And if I don't manage the symptoms of the disorder, then I will have functional impairments and I don't want functional impairments. So if part of my treatment plan is taking medications every day, I'm going to be taking medications every day.
And I'm going to look into psychological tools that I know help my deficits in executive functioning. You know, there are things, a lot of it is because you have deficits in executive functioning, creating calendars is super helpful. I'm going to have a to-do list. And no matter how bad I'm feeling every morning, I have a big note on my computer that says, look at your calendar. So the first thing I want to do is going to look at my calendar.
And I'm going to write a to-do list because to-do lists externalizing my working memory is very helpful for me. And I also know that if I don't exercise, if I eat unhealthy, then I'm going to be more symptomatic. And if I'm more symptomatic, I'm going to be causing more problems. So I'm going to do the best that I can to prioritize those things. So the internal locus there is that applying this label to me helps me to know the things that I need to do to take care of myself, to minimize the way that my executive deficits impact my life.
Now, the external locus of control is someone who says, look, I'm not responsible for the mistakes I make, for the things I do, because I have ADHD. Yeah, I'm texting while you're talking to me, but I have ADHD. It's not my fault. Or they'll think, you know, this is biological. That means it's medications, and I don't need to do therapy. I don't need to have a calendar or task list because I have ADHD, so those things are really hard for me, and this is a biological illness.
I don't make dopamine, so therefore I'm unable to do those things, and that's not my fault. And if I forget my partner's birthday and they're upset at me, I get upset at them back and say, it's not my fault I have ADHD. So the gist is that any sort of label or disorder doesn't dictate how you internalize what it means to have disorder. And people who have an internal locus of control believe that they have control over the outcomes of the events in their lives based on their own actions and their own decisions and their own efforts.
And in my opinion, having an internal locus of control is the healthiest way to internalize your disability. That means you still have personal responsibility over the mistakes you make. It means you have a problem-solving orientation. Whenever you face a challenge, you're proactive. You don't throw your hands up and say, it's not my fault. People like this have better coping skills and people with an internal locus of control have higher self-esteem.
They have better academic and job performance. Whereas taking an external locus of control approach to your disorder will make you feel helpless. It'll make you feel like you're not in control. Yeah. And I bring this up because as a clinician myself, When we're applying these diagnoses to people, I think it's important that we encourage the person to have an internal locus of control with regard to their diagnosis so that they have a healthy relationship with the idea that they have this problem.
I might have gone a little off the rails there. But I just want to move on. I do want to talk a little bit about the history of the diagnosis. And I think that's helpful. The history is super important to kind of get an idea of how we develop the ideas of the disorder and maybe some of the associations we have with the disorder. And it's confusing that it used to be ADD.
Now it's ADHD. So I'll just talk a little bit about kind of how the disorder came to be. So people, descriptions of kids with symptoms of inattention, hyperactivity, and impulsivity have been in literature from the 1900s. Of course, people existed who had those things, but in terms of people writing about it, no. Now, there was a concept of what was called minimal brain damage. And this was related to the fact that there was an epidemic of encephalitis in like the 1920s.
So from like 1916 to like 1930 ish. There was an outbreak of what was called encephalitis lethargica, also known as sleeping sickness. And encephalitis just refers to inflammation of the brain. You can see it in the word. Encephal means brain. Itis means inflammation. So they saw a lot of kids with encephalitis. brain damage as a result of an infection. And they noted that it was similar to hyperactive kids and hyperactive animals who had frontal lobe ablation.
So they basically had direct damage to their frontal lobe. So these people saw a very big correlation between the physiological explanation of behavioral disorders. So it led to the idea and the concept of brain damage. So if someone had minimal brain damage, that they would exhibit hyperactive signs. And because they didn't always have imaging or ways to look at the brain, people would be diagnosed with minimal brain damage even when the damage couldn't be demonstrated.
because it was just presumed to be present. So they presumed that there was something that occurred that they didn't see, whether it was an infection or a traumatic injury. Now the concept of minimal brain damage, the symptoms match the DSM criteria for ADHD. So in some sense, it was an antecedent to ADHD. and of course the you know the idea of minimal brain damage really emphasizes neurological factors rather than environmental or social factors it's not looking at development it's not looking at how the person was raised it's saying that this person had brain damage now i think it's interesting that this eventually kind of transformed into diagnoses that would become adhd because it really talks about how the disorder really stemmed from a neurological disorder.
So it's not surprising that there's such a biological, a neurological focus on the disorder. So of course, the term minimal brain dysfunction was too general, and it was eventually replaced by more specific labels. The DSM-2 had the diagnosis of hyperkinetic reaction of childhood, And how it was defined, it was characterized by overactivity, restlessness, distractibility, short attention span, especially in younger kids, and the behavior diminishes by adolescence.
By the DSM-3, the focus on hyperactivity was shifted towards an emphasis on attention deficits. So one of the main researchers argued that deficits in sustained attention and impulse control were more central and significant than the hyperkinetic things that were going on. And they also noticed that these symptoms responded the best to stimulants. So the DSM-3 renamed it attention deficit disorder and then with or without hyperactivity. So it kind of took the position that hyperactivity was no longer an essential feature of the diagnosis.
Now the DSM-3 treatment revision, it wasn't clear if hyperactivity versus without hyperactivity was qualitatively the same kind of process going on. So to match what was empirically being studied, they removed the idea that there were two subtypes and just mushed it all together into one and renamed it ADHD. I guess to say that another way to make it more clear, DSM-3, it was ADD or ADD with hyperactivity.
And then they moved it so they just lumped it all together to ADHD. Now, the DSM-IV had, at this point, they had several studies that looked at different subtypes. And they found that kids with hyperactivity differed from those who didn't have the hyperactivity. So there were almost like two different subtypes. There was the hyperactive, hyperkinetic subtype. And then there was the inattentive subtype. These were kids who were more daydreamy, hypoactive didn't do particularly well in academics but they weren't as aggressive and they were less rejected by their peers as a result of like their hyperactivity so the a large field trial essentially identified three different subtypes there was predominantly inattentive predominantly hyperactive and then combined.
But again, they're all called ADHD. So just so people are aware, now in the DSM-5, we still follow that. So we call it ADHD regardless of if there is hyperactivity. So people who are strictly inattentive and not paying attention, we still would call them attention deficit hyperactivity disorder, even though the hyperactivity isn't necessarily appropriate. And then I guess I kind of forgot. The DSM-IV was where adult ADHD was officially recognized.
And that's where it was first acknowledged that the disorder could persist beyond childhood. The DSM-V kind of just made some like minor adjustments. So they lowered the number of symptoms for adults from six to five. And they clarified that symptoms must be present before the age of 12 instead of seven. One thing that I think is actually reflective of what I see clinically, hyperactivity in adults actually a lot of times transforms into restlessness, into fidgeting, into inability to relax.
You don't see overt hyperkinetic activity. Instead, you might see restlessness or maybe substance use connected to this inner restlessness, but you might not see the hyperactive kid that you kind of picture. All right. I do want to move on. By the last thing I'll probably talk about, is it biological or not? The question itself doesn't mean as much as it sounds. The thing that I often see cited as to, you know, quote unquote, proof that it's biological is how heritable the ADHD is.
So ADHD is highly heritable. You see heritability estimates at like 70 to 80%. So people who don't understand what heritability means say they look at the number and they go, oh, it's 70 to 80% biological, which that's not what it means. heritability is really, it's confusing and it's easily misunderstood. So it's not saying the probability of having ADHD, it's a population level measure. So it's saying the percentage of the variation that you see in a population that can be explained by genetics.
So the fact that it's 70 to 80%, 70 to 80% of the variants can be explained by genetics. So what this is saying is just that highly heritable traits are more likely to be passed on to the next generation than less heritable traits. But this doesn't mean that it's purely biological or that an individual is fated to have it. So it's a population measure, not a measure for the individual.
So it reflects the degree that the differences are different across a population. So it doesn't say that a specific person's cause of ADHD is solely by their genes. And just because ADHD has a high heritability, environmental factors still play a major role, as does the environment between genes and in the environment. And even the most biological traits have an interplay between multiple genes and environmental inputs. So high heritability does not mean that it's unchangeable.
It doesn't mean that it's guaranteed to happen. It doesn't mean that it's purely biological or that it's immutable. And it doesn't mean that environmental interventions don't help. So it's important to note that there are genetic variants that are associated with ADHD, but none of them are specific for ADHD. There's not an ADHD gene. There never will be an ADHD gene. So it's a complex interplay of multiple genes that may increase your risk of having it and the environment.
It's not someone has, you know, a gene that causes ADHD. And maybe looking at other disorders with high heritability can maybe help you kind of think about this. So something like obesity has a relatively high heritability, probably like 40 to 70%, so not as high as ADHD, but still relatively high. Now, that doesn't mean if someone you hear that and you don't think that if someone has obese parents that they're fated to be obese or if someone has obese relatives that they should throw their hands up and say that there's nothing I can do about this.
And also that it doesn't mean that it's biological. We wouldn't say that someone being obese is a biological predestination and just how it doesn't the same goes for ADHD. All right, I'm starting to fade, so I'm going to cap it here. Hopefully, when Dr. Fu returns, we can have a juicy, juicy podcast debating kind of more of this stuff, kind of getting more into the juicy, opinion-y stuff.
But I'm going to cap it here.