ADHD & How Anyone Can Improve Their Focus | Huberman Lab Essentials

Welcome to Huberman Lab Essentials, where we revisit past episodes for the most potent and actionable science-based tools for mental health, physical health, and performance. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today, we are going to talk all about attention deficit hyperactivity disorder, or ADHD. Now, just a quick reminder that anytime we discuss a psychiatric disorder, it's important that we remember that all of us have the temptation to self-diagnose, or to diagnose others. The clear and real diagnosis of ADHD really should be carried out by a psychiatrist, a physician, or a very well-trained clinical psychologist. So, right now, the current estimates are that about 1 in 10 children, and probably more, have ADHD. Now, fortunately, about half of those will resolve with proper treatment. But, the other half typically don't. The other thing that we are seeing a lot nowadays is increased levels of ADHD in adults. For sake of today's discussion, attention, focus, and concentration are essentially the same thing. So, people with ADHD have trouble holding their attention. What is attention? Well, attention is perception. It's how we are perceiving the sensory world. For instance, right now, you're hearing sound waves. You are seeing things. You are sensing things against your skin, but you are only paying attention to some of those. And the ones that you're paying attention to are your perceptions. So, if you hear my voice, you are perceiving my voice. You are not paying attention to your other senses at the moment. Okay? You might even be outside in a breeze, and until I said that, you might not be perceiving that breeze, but your body was sensing it all along. So, attention and focus are more or less the same thing, but impulse control is something separate. Because impulse control requires pushing out or putting the blinders on to sensory events in our environment. It means lack of perception. Impulse control is about limiting our perception. People with ADHD have poor attention, and they have high levels of impulsivity. Yes, they are distractible. Yes, they are impulsive. Yes, they are easily annoyed by things happening in the room. They sometimes have a high level of emotionality as well. However, people with ADHD can have a hyperfocus, an incredible ability to focus on things that they really enjoy or are intrigued by. Now, this is a very important point because people with ADHD have the capacity to attend, but they can't engage that attention for things that they don't really, really want to do. There are a couple other things that people with ADHD display quite often. One is challenges with time perception. People with ADHD often run late. They often procrastinate. But, what's interesting and surprising is that if they are given a deadline, they actually can perceive time very well. And they often can focus very well if the consequences of not completing a task or not attending are severe enough. If they're not really concerned about a deadline or a consequence, well, then they tend to lose track of time, and they tend to underestimate how long things will take. The other thing that people with ADHD have real trouble with is so-called working memory. Now, you might think that people with ADHD would have really poor memories, but in fact, that's not the case. People with ADHD often can have a terrific memory for past events. They can remember upcoming events quite well. Their memory is clearly working. However, one aspect of memory in particular that we call working memory is often disrupted. Working memory is the ability to keep specific information online to recycle it in your brain over and over again so that you can use it in the immediate or short-term. A good example of this would be you meet somebody, they tell you their name, they give you their phone number verbally, and you have to walk back to your phone and enter it into your phone. People without ADHD might have to put some effort into it. It might feel like a bit of a struggle, but typically they would be able to recite that phone number in their mind over and over and then put it into their phone. People with ADHD tend to lose the ability or lack the ability to remember things that they just need to keep online for anywhere from 10 seconds to a minute or two. Okay, so we've more or less established the kind of menu of items that people with ADHD tend to have. Some have all of them, some have just a subset of them. Their severity can range from very intense to mild, but in general it's challenges with attention and focus, challenges with impulse control, they get annoyed easily, they have kind of an impulsivity, they can't stay on task, time perception can be off, and they have a hard time with anything that's mundane that they're not really interested in. But again, I just want to highlight that people with ADHD are able to obtain heightened levels of focus, even hyperfocus, for things that are exciting to them and that they really want to engage in. So, let's drill into this issue of why people with ADHD actually can focus very intensely on things that they enjoy and are curious about. Now, enjoyment and curiosity, they're just the way that we describe our human experience of liking things, wanting to know more about them. But from a neurobiological perspective, they have a very clear identity and signature. And that's dopamine. Dopamine is released from neurons. It's what we call a neuromodulator. And in particular, dopamine creates a heightened state of focus. It tends to contract our visual world. And it tends to make us pay attention to things that are outside and beyond the confines of our skin. It's what we call exteroception. So, as I mentioned earlier, you have all these senses coming in. And you can only perceive some of them because you're only paying attention to some of them. Dopamine, when it's released in our brain, tends to turn on areas of our brain that narrow our visual focus and our auditory focus. So, it creates a cone of auditory attention that's very narrow. Creates a tunnel of visual attention that's very narrow. Whereas, when we have less dopamine, we tend to view the entire world. We tend to see the whole scene that we are in. We tend to hear everything all at once. So, as I describe this, hopefully you're already starting to see and understand how having dopamine release can allow a person, whether or not they have ADHD or not, to direct their attention to particular things in their environment. Right? So, now what we're doing is we're moving away from attention as this kind of vague, ambiguous term, and we're giving it a neurochemical identity, dopamine. And we are giving it a neural circuit identity. And just to put a little bit of flavor and detail on which neural circuits those are, I want to discuss two general types of neural circuits that dopamine tends to enhance. The first one is called the default mode network. The default mode network is the network of brain areas in your brain and my brain and in everybody's brain that is active when we're not doing anything, when we're just sitting there idle, at rest. The other set of circuits that we're going to think about and talk about with respect to ADHD, are the task networks. The networks of the brain that make you goal-oriented. And those are a completely different set of brain areas. However, the default mode network and these task networks are communicating with one another, and they're doing that in very interesting ways. Frontal cortex, no surprises in the front, and you have a dorsal, the top, and side, lateral part, dorsolateral prefrontal cortex. And then you have a brain area called the posterior cingulate cortex. And then you have an area called the lateral parietal lobe. Again, you don't need to remember these names, but these are three brain areas that normally are synchronized in their activity. So, when one of these areas is active in a typical person, the other areas would be active as well. And in a person with ADHD, or even a person who has subclinical ADHD, or in any human being who hasn't slept well, what you find is the default mode network is not synchronized. These brain areas are just not playing well together. Now, the task networks include a different set of structures. It still involves the prefrontal cortex, but it's a different part of the prefrontal cortex, okay? It tends to be the medial prefrontal cortex. And there are some other brain areas that the medial prefrontal cortex is communicating to all the time, mainly to suppress impulses. Anytime you're restricting your behavior, these task-directed networks are very active. Okay? Now, normally in a person without ADHD, the task networks and the default mode networks are going in kind of seesaw fashion. They are actually what we call anti-correlated. In a person with ADHD, they actually tend to be more correlated. The default mode networks and the task networks are actually more coordinated. And we can now confidently say, based on brain imaging studies, that when somebody gets better when they're treated for ADHD or when they age out of ADHD, as sometimes is the case, that the default mode networks and the task networks tend to become anti-correlated again. What dopamine is doing in this context is dopamine is acting like a conductor. Dopamine is saying this circuit should be active then that circuit should be active. It should be default mode network and then when the default mode network is not active, then it should be the task network. And in ADHD, there's something about the dopamine system that is not allowing it to conduct these networks and make sure that they stay what, you know, the engineers or physicists or mathematicians would say out of phase to be anti-correlated. So, what exactly is going on with the dopamine system in people with ADHD? And what's going on with the dopamine system in people that have terrific levels of attention for any task? Well, in the year 2015, an important paper came out and it formalized the so-called low dopamine hypothesis of ADHD. It turns out that if dopamine levels are too low in particular circuits in the brain, that it leads to unnecessary firing of neurons in the brain that are unrelated to the task that one is trying to do and that is unrelated to the information that one is trying to focus on. So, if you think back before you've got this default mode network and a task-related network, and they need to be in this kind of concert of anti-correlation and in ADHD, they're firing together. Well, the problem seems to be that when dopamine is low, neurons fire more than they should in these networks that govern attention. This is the so-called low dopamine hypothesis. And if you start looking anecdotally at what people with ADHD have done for decades, what you find is that they tend to use recreational drugs or they tend to indulge in non-drug stimulants. So, things like smoking a half a pack of cigarettes and drinking four cups of coffee a day. Or, if the person had access to it, using cocaine as a recreational drug or amphetamine as a recreational drug. All of those substances that I just described, in particular cocaine and amphetamine, but also coffee and cigarettes, increase levels of multiple neurotransmitters, but all have the quality of increasing levels of dopamine in the brain and in particular in the regions of the brain that regulate attention and these task-related and default mode networks. Now, young children, fortunately, don't have access to those kinds of stimulants most of the time, but if you look at children, even very young children with ADHD, they show things like preference for sugary foods, which also act as dopamine-inducing stimulants. For a long time it was thought that children with ADHD consume too many sugary foods or drank too much soda. Or, adults with ADHD would take recreational drugs like methamphetamine or cocaine or would drink coffee to excess or smoke cigarettes to excess because they had poor levels of attention and because they couldn't make good decisions. They were too impulsive and so forth. Knowing what we now know about dopamine and the fact that having enough dopamine is required in order to coordinate these neural circuits that allow for focus and quality decision-making. An equally valid idea is that these children and these adults are actually trying to self-medicate by pursuing these compounds, right? Things like cocaine lead to huge increases in dopamine. Well, what happens with when somebody with ADHD takes that drug? It turns out they actually obtain heightened levels of focus. Their ability to focus on things other than things they absolutely care intensely about goes up. Likewise, children who consume anything that increases their levels of dopamine, if those children have ADHD, they tend to be calmer. They tend to be able to focus more. So, dopamine and low levels of dopamine apparently are what's wrong in people with ADHD. That dopamine hypothesis is what led to the idea that treating people, children and adults included, with dopaminergic compounds would somehow increase their ability to focus. And if you look at the major drugs that were developed and now marketed by pharmaceutical companies for the treatment of ADHD, those drugs have names like Ritalin. Nowadays, it's typically things like Adderall, modafinil, and some of the other derivatives. They all serve to increase levels of dopamine, in particular dopamine in the networks that control task-directed behavior and that coordinate the default mode network and these task-related networks. Let's take a step back for a second and just ask, what are these drugs? We know they increase dopamine, but what are they really? Well, Ritalin, also called methylphenidate, is very similar to amphetamine, speed, or what's typically called speed in the street drug uh nomenclature. Adderall is basically a combination of amphetamine and dextroamphetamine. Now, some of you probably realize this that Adderall is amphetamine, but I'm guessing that there a good number of you out there, perhaps even parents and kids that don't realize that these drugs like cocaine and amphetamine, methamphetamine, which are incredibly dangerous and incredibly habit-forming and have high potential for abuse, well, the pharmaceutical versions of those are exactly what are used to treat ADHD. Now, they're not exactly like cocaine or methamphetamine, but they are structurally and chemically very similar, and their net effect in the brain and body is essentially the same, which is to increase dopamine primarily, but also to increase levels of a neuromodulator called epinephrine or norepinephrine, also called noradrenaline and adrenaline. Those names are the same. So, what I'm essentially saying is that the drugs that are used to treat ADHD are stimulants. And they look very much like, in fact, nearly identical to some of the so-called street drug stimulants that we all hear are so terrible. However, I do want to emphasize that at the appropriate dosages and working with a quality psychiatrist or neurologist or family physician, does have to be a board-certified MD that prescribes these things, many people with ADHD achieve excellent relief with these drugs. Not all of them, but many of them do, especially if these treatments are started early in life. So, now, knowing what these drugs are, I want to raise the question of why prescribe these drugs? Children have a brain that's very plastic, meaning it can remodel itself and change in response to experience very, very quickly compared to adults. Taking stimulants as a child, if you are a child diagnosed with ADHD, allows that forebrain task-related network to come online, to be active at the appropriate times. And because those children are young, it allows those children to learn what focus is and to sort of follow or enter that tunnel of focus. Now, by taking a drug, it's creating focus artificially. It's not creating focus because they're super interested in something. It's chemically inducing a state of focus. And, let's face it, a lot of childhood and school and becoming a functional adult is about learning how to focus even though you don't want do something. So, what are we to make of this whole picture? That we need more dopamine, but these kids with ADHD, they're getting their dopamine by way of a drug, which is for all the world, amphetamines. What are the long-term consequences? What are the short-term consequences? Well, in order to get to some of those answers, I went to one of my colleagues, a pediatric neurologist that specializes in the treatment of epilepsy and ADHD in kids of all ages, from age 3 to 21. I asked the following questions. First of all, I asked, "What do you think about giving young kids amphetamine, provided that the lowest possible dose is used and that that dosage is modulated as they grow older and develop those powers of attention?" Their observation was that they've seen more kids benefit than not benefit from that. Now, the fact that this person, this now friend of mine and colleague of mine, has so much expertise in the way that the brain works, and is considering putting their child on such medication, I said, "You know, why wouldn't you wait until your kid reaches puberty? I mean, we know that in boys and in girls, there are increases in testosterone and estrogen during puberty that dramatically change the way that the body appears, but also that dramatically change the way that the brain functions. In particular, we know this, that puberty triggers the activation of so-called fronto-temporal task-related executive functioning. That's just fancy science speak for being able to focus, being able to direct your attention, being able to control your impulses." And their answer was very specific and I think very important. What they said was, "Look, neural plasticity is greatest in childhood and tapers off after about age 25, but neural plasticity from age 3 until age 12 or 13 is exceedingly high. If you have the opportunity to work with a quality physician and treat these things early, these drugs can allow these frontal circuits, these task-related circuits, to achieve their appropriate levels of functioning and for kids to learn how to focus in a variety of different contexts. So, we've talked about the neural circuits of focus and the chemistry of focus, but we haven't talked yet about what would make us better at focusing and what focusing better really is. So, let's take a step back and think about how we focus and how to get better at focus. And I'm going to share with you a tool for which there are terrific research data that will allow you in a single session to enhance your ability to focus in theory forever. What we're about to talk about is when attention works and when attention falters. And what we are specifically going to talk about are what are called attentional blinks. Not actual eye blinks. Attentional blinks are really easy to understand if you think about a Where's Waldo task. You know this task, Where's Waldo, where you know, there a bunch of people and objects and things in a in a picture and somewhere in there is Waldo with the striped hat and the glasses and kind of a skinny dude, and you have to find Waldo. And so, it's a visual search and it's visual search for an object that has distinct features, but is embedded in this ocean of other things that could easily be confused as Waldo. So, you tend to look for Look for Look Look Look Look Look Look. When you find Waldo or when you search for a target in some other visual search task, at that moment, your nervous system celebrates a little bit. And it celebrates through the release of neurochemicals that make you feel good. You found it. And you pause. Now, the pause is interesting because when you pause, what we know from many experiments is that in that moment of pause and mild celebration, however mild, you are not able to see another Waldo sitting right next to it. So, what this means is in attending to something, in searching, and in identifying a visual target, your attention blinked. It shut off for a second. If you see something that you're looking for or you're very interested in something, you are definitely missing other information. In part because you're over focusing on something. And this leads to a very interesting hypothesis about what might go wrong in ADHD, where we've always thought that they cannot focus, and yet we know they can focus on things they care very much about. Well, maybe, just maybe, they are experiencing more attentional blinks than people who do not have ADHD. And indeed, there are data now to support the possibility that that's actually what's happening. So, what they really need is this property that we call open monitoring. First of all, your visual system has two modes of processing. It can be highly focused, a soda straw view. However, there's also a property of your visual system that allows you to dilate your gaze to be in so-called panoramic vision. Panoramic vision is actually mediated by a separate stream or set of neural circuits going from the eye into the brain, and it's a stream or set of circuits that isn't just wide angle view, it also is better at processing things in time. It's frame rate is higher. You can use panoramic vision to access the state that we call open monitoring. When people do that, they are able to attend to and recognize multiple targets. So, this is something that can be trained up and people can practice, whether or not they have ADHD or not. What it involves is learning how to dilate your gaze consciously. That's actually quite easy for most people. You can consciously go into open gaze and then you can contract your field of view as well. That might not seem like a significant or unusual practice or that it would have any impact at all, but remarkably just doing that once for 17 minutes significantly reduced the number of attentional blinks that people would carry out. In other words, their focus got better in a near permanent way without any additional training. Now let's talk about actual blinks, the sort that you do with your eyelids. Believe it or not your perception of time is also changed on a rapid basis, moment-to-moment basis by how often you blink. I want to just emphasize one study in particular which is quite appropriately titled Time Dilates After Spontaneous Blinking. They examined the relationship between fluctuations in timing and blinking. And to make a long story short, what they found is that right after blinks, we reset our perception of time. Now what's interesting and will immediately make sense to you as to why this is important is that the rate of blinking is controlled by dopamine. So what this means is that dopamine is controlling attention, blinks relate to attention and focus and therefore the dopamine and blinking system is one way that you constantly modulate and update your perception of time. And fortunately, it's also one that you can control. So the basic takeaway of this study was that blinking controls time perception, but also that levels of dopamine can alter your sense of time and stay with me here and that blinking and dopamine are inextricably linked. They are working together to control your attention. Let's remember back to the very beginning of the episode. What's going on in people with ADHD? They are not good at managing their time. They tend to run late or they are disorganized. Their dopamine is low. We know that as well. And so they are underestimating time intervals. And so it makes perfect sense that they would be late. It makes perfect sense that they would lose track of time or the ability to focus. This is really exciting because what it means is that children with ADHD, adults with ADHD, or people with normal levels of focus that want to improve their ability to focus can do so through a training that involves learning how often to blink and when and how to keep their visual focus on a given target. And it turns out this study has actually been done, entitled Improvement of Attention in Elementary School Students Through Fixation Focus Training Activity. I won't go through all the details, but what they found was a short period of focusing on a visual target allowed these school children to greatly enhance their ability to focus on other types of information. And a significant component of the effect was due to the way that they were controlling the shutters on their eyes, their eyelids, and controlling their blinks. So what they did in this study is they had these kids focus their visual attention on some object that was relatively close, like their hand, for a minute or so, which actually takes some effort if you try and do that. They were allowed to blink. It only took a few minutes each day to do this. 30 seconds in one condition or maybe a minute, and then at another station of looking a little bit further out and a little bit further out. However, there was an important feature of this study that is definitely worth mentioning, which is before they did this visual focus task or training they did a series of physical movements with the kids so that the kids could sort of eliminate or move out some of their desire to move and would thereby enhance their ability to sit still. Now, it should make perfect sense that these shutters on the front of your eyes, they aren't just there for winking and they aren't just there for cosmetic purposes. They are there to regulate the amount of information going into your nervous system and they're there to regulate how long you are bringing information into your nervous system and in what bins, how widely or finely you are binning time is set by how often you blink and how widely or specifically you are grabbing attention from the visual world is set by whether or not you're viewing things very specifically like a crosshair or through a soda straw view like this or whether or not you are in this panoramic sort of whole environment mode, this kind of fisheye lens or wide-angle lens mode. So, now I want to switch back to talking about some of the drugs that are typically used to access those systems, prescription drugs. And I want to talk about some of the new and emerging non-prescription approaches to increasing the levels of dopamine, acetylcholine, and serotonin in the brain using various supplement-type compounds because several of them are showing really remarkable efficacy in excellent peer-reviewed studies. So, before moving to some of the newer atypical compounds and things sold over the counter, I'd like to just briefly return to the classic drugs that are used to treat ADHD. These are the ones I mentioned earlier, methylphenidate, also called Ritalin, modafinil, armodafinil is another one, and Adderall. Again, all of these work by increasing levels of dopamine and norepinephrine. I think it is important to understand the extent to which they all carry more or less the same side effect, such as high propensity for addiction and abuse, amphetamines of any kind, as well as cocaine, can cause sexual side effects because they're vasoconstrictors. So, these drugs are not without their consequences. In addition, they almost all carry cardiac effects, right? They increase heart rate, but they also have effects on constriction of blood vessels and arteries and veins and so forth in ways that can create cardiovascular problems. The best use of things like Adderall, modafinil, armodafinil, and Ritalin is going to be to combine those treatments with behavioral exercises that actively engage the very circuits that you're trying to train up and enhance. And then, perhaps, I want to highlight perhaps, tapering off those drugs so that then one can use those circuits without any need for chemical intervention. So, despite any controversy that might be out there, I think it's fair to say that the consumption of omega-3 fatty acids can positively modulate the systems for attention and focus. So, then the question becomes, how much EPA, how much DHA, does that differ for uh what's helpful for depression, etc.? And actually, it does differ. In reviewing the studies for this, it appears that a threshold level of 300 mg of DHA turns out to be an important inflection point. So, typically, fish oils or other sources of omega-3s will have DHA and EPA, and typically, it's the EPA that's harder to get at sufficient levels. Meaning, you have to take quite a lot of fish oil in order to get above that 1,000 mg or 2,000 mg threshold to improve mood and other functions. But, for sake of attention, there are 10 studies that have explored this in detail, and while the EPA component is important, the most convincing studies point to the fact that getting above 300 mg per day of DHA is really where you start to see the attentional effects. Now, fortunately, if you're getting sufficient EPA for sake of mood and other biological functions, almost without question, you're getting 300 mg or more of DHA. What's interesting is that there's another compound, phosphatidylserine, that has been explored for its capacity to improve the symptoms of ADHD. Phosphatidylserine taken for 2 months for 200 mg per day was able to reduce the symptoms of ADHD in children. It has not been looked at in adults yet, as at least as far as I know, but that this effect was greatly enhanced by the consumption of omega-3 fatty acids. So, now we're starting to see synergistic effects of omega-3 fatty acids and phosphatidylserine. So, I'd like to talk about the drug modafinil and the closely related drug armodafinil, that's AR modafinil, because modafinil and armodafinil are gaining popularity out there both for treatment of ADHD and narcolepsy, but also for communities of people that are trying to stay awake long periods of time. So, it's actively used in the military, by first responders. It's gaining popularity on college campuses, and people are using it more and more as an alternative to Adderall and Ritalin and excessive amounts of coffee. It does increase focus and to a dramatic extent. Want to emphasize that unlike Ritalin and Adderall, modafinil and armodafinil are weak dopamine reuptake inhibitors, and that's how they lead to increases in dopamine. Now, you may notice that I haven't talked much about acetylcholine. Acetylcholine is a neurotransmitter that at the neuron-to-muscle connections, the so-called neuromuscular junctions, is involved in generating muscle contractions of all kinds for all movements. Acetylcholine is also released from two sites in the brain. There is a collection of neurons in your brain stem that send projections forward, kind of like a sprinkler system that's very diffuse, to release acetylcholine. And those neurons reside in an area or a structure that's called the pedunculopontine nucleus, the PPN. And then there's a separate collection of neurons in the basal forebrain called, unimaginatively, nucleus basalis, the nucleus at the base. And they also hose the brain with acetylcholine, but in a much more specific way. So one is sort of like a sprinkler system and the other one is more like a fire hose to a particular location. And those two sources of acetylcholine collaborate to activate particular locations in the brain and really bring about a tremendous degree of focus to whatever is happening at those particular synapses. So now you have an example and you have an understanding and hopefully a picture in your mind of how the all this is working. Not surprisingly then, drugs that increase cholinergic or acetylcholine transmission will increase focus and cognition. One such compound is so-called alpha GPC, which is a form of choline and increases acetylcholine transmission. Dosages as high as 1,200 mg per day, which is a very high dosage, spread out typically it's 300 or 400 mg spread out throughout the day, have been shown to offset some of the effects of age-related cognitive decline, improve cognitive function in people that don't have age-related cognitive decline. Typically when people are using alpha GPC to study or to enhance learning of any kind, they will take somewhere between 300 and 600 mg. That's more typical. Again, you have to check with your doctor, you have to decide if the safety margins are appropriate for you. And there are some over-the-counter compounds that are in active use out there for treatment of ADHD and in use for simply trying to improve focus. L-tyrosine, it's an amino acid that acts as a precursor to the neuromodulator dopamine. The dosaging can be very tricky to dial in. Sometimes it makes people feel too euphoric or too jittery or too alert that they are then unable to focus well. So, the dosage ranges are huge. You see evidence for 100 mg all the way up to 1,200 mg. It's something that really should be approached with caution, especially for people that have any kind of underlying psych psychiatric or mood disorder because dysregulation of the dopamine system is you know, central to many of the mood disorders such as depression, but also especially mania, mania, bipolar disorder, schizophrenia, things of that sort. So, it's something that really should be approached with caution. Everybody nowadays seems to have a smartphone. They grab our attention entirely, but within that small box of attention, there are millions of attentional windows scrolling by, right? So, just because it's one device that we look at does not mean that we are focused. We are focused on our phone, but because of the way in which context switches up so fast within the phone, it's thought that the brain is struggling now to leave that rapid turnover of context. Even though there are trillions, infinite number of bits of information in the actual physical world, your attentional window, that aperture of constriction and dilating that visual window is the way in which you cope with all that overwhelming information typically. Well, within the phone, your visual aperture is set to a given width, and within there, your attentional window is grabbing at near infinite number of bits of information, colors, movies. And so, the question is, does that sort of interaction on a regular basis lead to deficits in the types of attention that we need in order to perform well in work, in school, relationships, et cetera? And the short answer is, yes, we are inducing a sort of ADHD. I'm not here to tell you what to do, but I think whether or not you have ADHD or not, if you're an adolescent, limiting your smartphone use to 60 minutes per day or less, and if you are an adult, to 2 hours per day or less is going to be among the very best ways to maintain your ability to focus at whatever level you can now. And as I always say, most of the things that we get recognized for in life, success in life, in every endeavor, whether or not it's school, relationships, sport, creative works of any kind, are always proportional to the amount of focus that we can bring that activity. It is important to rest, of course, to get proper sleep, but I stand behind that statement, and I leave you with that about attention and cell phones and how cell phones are indeed eroding our attentional capacities. So, I realize I covered a lot of information about ADHD and the biology of focus and how to get better at focusing. We talked about the behavioral and psychological phenotypes of ADHD. We talked about the underlying neural circuitry. We also talked about the neurochemistry, and we talked about the various prescription drug treatments that are aimed at that neurochemistry and aimed at increasing focus in children and adults with ADHD.