The Focus Trick I Wish I Knew Sooner
In this video, MD‑PhD neuroscientist Nick Norwitz shares a personal habit he credits for his academic success and uses it as a springboard to explore why many people struggle with focus. He outlines two long‑standing paradoxes in stimulant pharmacology – the inverted‑U performance curve and the “stimulant‑for‑hyperactivity” paradox – and then presents recent large‑scale fMRI research (≈12,000 children and additional adult scans) that shows stimulants primarily boost arousal and reward circuitry rather than the canonical attention networks. The data reveal that stimulants make the brains of sleep‑deprived individuals resemble those of well‑rested peers, suggesting that these drugs often act as a pharmacological substitute for missing sleep. Norwitz connects this to the brain’s master clock, the suprachiasmatic nucleus (SCN), explaining that delayed‑phase circadian timing (common in ADHD) forces many into chronic sleep debt, which in turn drives reliance on stimulants. He emphasizes that while true ADHD (a minority of prescriptions) does benefit from stimulants, much of the observed improvement may stem from compensating for sleep loss. The video concludes by hinting at practical tools—light exposure, melatonin timing, and consistent wake‑times—to reset the internal clock and reduce dependence on stimulants for focus.
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By the time I was 30, I had graduated valedictorian from Dartmouth with a perfect GPA, done my PhD at Oxford, then my MD at Harvard, and I always wondered how I did it because I promise you I am not a genius. But now I realize I had an unfair advantage because I did one simple thing daily that most university students are terrible at. And today I'm going to tell you about it, citing new science and giving you the not-so-secret secret to focus. Provided you can focus through this video. Let's begin. Have you ever had one of those days where you just can't focus? Maybe you didn't sleep well the night before. You sit down to write or read, finally start a project that's due tomorrow, and your mind is already somewhere else. You're checking your phone, you're scrolling Instagram, you're opening YouTube, you're clicking from one video to the next, and at some point you realize you can't even finish a single video before the urge to switch hits again. But don't click off. Because even as a trained MD-PhD neuroscientist who should know better and do better, I have those days too. I doomscroll Instagram sometimes, and honestly, if you looked at my algorithm, I'd be embarrassed. It's less education than relationship memes and Harry Potter conspiracy theories. And for me, these days show up seemingly out of nowhere, like a jack-in-the-box, and they absolutely wreck my productivity. In fact, Focus problems are so common nowadays that a lot of us have a running joke about our ADHD acting up.
I have a very short attention span.
But our point is very simple. You see, when— Oh,
look, a bird!
But here's the strange part: that joke might accidentally be right. Because the real reason you lost an afternoon to a wandering brain is stranger than a broken attention span. And a lot easier to fix. 2 paradoxes in the story that never really got explained. That's like prescribing 3 shots of espresso as a sleep aid. There's actually a ton of overlap. We need to talk about the clock inside your brain. This is boring. There's no dopamine here. Caffeine temporarily raises dopamine levels. The worry is what we might be quietly compensating for without even knowing it. And the result is 3 cataclysmic words. I did graduate valedictorian in college. And here's my secret. Today, I want to walk you through a fascinating study published in the journal Cell that suggests at least some of the cases we frame as attention problems and even ADHD might actually reflect another problem in disguise. We're going to get into that, and along the way, we'll uncover insights that will be useful whether you're someone living with true ADHD the parent of a child with ADHD, a struggling college student, or simply someone who occasionally struggles with focus, which honestly is 100% of us. And the last thing before we begin, I noticed about 76% of you who watch these videos aren't yet subscribed to this channel. So if you find this content valuable, please support me by clicking the subscribe button. It's a free thing you can do that really helps me out. It helps signal the algorithm, which gets these videos to more people. And if you turn on notifications, you'll be the first to know when a new one drops. But now, let's put on our focus caps and get into today's story. Here's our roadmap. In part 1, we're going to talk about 2 unresolved paradoxes that should get your mind spinning. In part 2, we're going to talk about the brain scans that changed the story. In part 3, we're going to talk about the clock in the middle of your brain. Then in part 4, we're going to resolve the paradoxes from earlier. And in part 5, we're going to talk about the paradoxes that we didn't get to. And in part 6, will we're going to talk about the paradoxes that culminate we didn't get to. with tools you can use, but you really do need to go through all 5 parts in sequence to understand what's going on in your brain. So let's start with part 1, the unresolved paradoxes. A little bit of history first, because it explains how we got this story so wrong. In 1929, scientists described how amphetamines keep your brain awake. And by 1937, a physician named Charles Bradley noticed the same class of drugs seemed to settle restlessness in kids and help them focus. So people drew the obvious conclusion: the drug must be turning up the brain's attention machinery. You fix the attention, you fix the behavior. It's a clean story, and on the surface it works. These drugs really do improve behavior on what appears to be attention-related tasks. But there are at least 2 cracks, 2 paradoxes in the story that That never really got explained. And I want you to hold them in your mind because we will answer them, and those answers will yield practical insights. But let's introduce them. Paradox 1 is the inverted U paradox. Basically, people who start out struggling improve on stimulants. They move towards the peak. But people who already perform well, when they take stimulants, they get no benefit and might even have their performance harmed when taking stimulants. Now, if these drugs just improved attention, we'd expect everyone to get a boost, not have some people get harmed by stimulants in terms of cognitive performance. That's paradox 1. Paradox 2 is even stranger: the stimulant for hyperactivity paradox. These are stimulants, right? But we give them to kids who are hyperactive to calm them down. So if the drug is a stimulant, why would it settle someone down? That's like prescribing 3 shots of espresso as a sleep aid. It makes no sense.
Now, Hammy, go!
No!
So those are the paradoxes we will answer later, but let's get into the data. A research team then went looking with advanced brain imaging to see what these stimulant medications actually do in a human brain, and what they found was not what I expected. Stimulants did not act through attention networks at all. They acted on something else. But you'll need to hold your attention to find out what that is. Which brings us to part 2, the brain scans that changed the story. So this is what the researchers did exactly. They took functional MRI scans, which are effectively high-resolution videos of brain activity, from nearly 12,000 children. They then chased those data with scans from adults both on and off stimulants to better generalize the findings to children and adults. And they asked a very simple question. When someone takes a stimulant medication, which brain networks actually change? So what did they find? Stimulants improved connectivity in the brain's sensory and motor regions. You can see that in purple. And it activated the reward networks. That's in black. So in other words, stimulants push the gas pedal on arousal and motivation. But what it did not touch in either the children or the adults was the attention system. That's in yellow. That's the very circuitry everyone assumes these drugs are repairing, and they're not even touching it. And that might sound like a subtle and purely academic distinction, but it's not. And you should 100% care if something you do to your brain impacts attention, arousal, or motivation, because it's by understanding what buttons we're pressing in the brain that we develop practical insights and protocols. Now, let's explore why this is so important, starting with a sad but really unsurprising statistic. The research team noticed that only 48% of the children in the study were getting the recommended amount of sleep for their age. And honestly, the fraction of adults getting sufficient quality sleep is probably even worse— worse than half. So the next question they then asked is, how does stimulant use impact the brain as compared to actually good sleep? And effectively, the stimulants made the brain of an underslept, poorly slept child look similar to that of a well-rested, well-slept child. Now, to be very clear, this does not mean that these medications are a replacement for all the functions of sleep. They are not. But insofar as brain arousal and reward systems go, the drug, the stimulant drug, made the underslept brain look like it got better sleep the night before. Or if you want an analogy, it's like taking a painkiller for a broken ankle. The symptoms improve, but the underlying injury— sleep deprivation— is still there. That said, credit where it's due, because stimulants actually improve children's grades as well, but not for every child. And this is important. Underslept children who took a stimulant earned grades that were significantly better than underslept children who did not. So basically, if the kids were sleep deprived and took a stimulant, it helped them However, when children were well-rested, those who took a stimulant did not experience any performance benefits, so simply put, the stimulants in many children only worked when the kids hadn't slept well. The implication, therefore, is uncomfortable but really important: for a meaningful slice of children who take stimulants routinely, and adults as well, the stimulant might be functioning, at least in part, as a substitute for the sleep that they aren't getting. Now, I do want to be careful because for patients with true ADHD, which is actually less than half of the children prescribed these drugs, they do benefit from what we call stimulants. So this is not an argument to throw out a medication. The worry is what we might be quietly compensating for without even knowing it. Because if you lean on a stimulant to cover up for chronic sleep loss, you carry the cost of that sleep loss for years— mood, stress at the cellular level, the whole kit and caboodle. But I'm going to be honest with you and break the I'm gonna break the fourth wall here for a moment. When I wrote out this script, I swear I thought the expression was kitten caboodle, like as in baby cat. Now I feel like an idiot and sorry for distracting you, but in all seriousness, this raises the obvious question: if sleep is the thing hiding underneath, or sleep deprivation, why are so many of these brains short on sleep in the first place? And for that answer, We need to talk about the clock inside your brain, which is part 3, the clock in the middle of your brain. Because deep in your brain is a cluster of neurons called the suprachiasmatic nucleus, or SCN. It is the master pacemaker that runs your body's daily 24-hour cycle. It decides when you release melatonin, when you feel sleepy, when you feel sharp. In most people, it's tuned so that sleepiness shows up at a socially convenient hour, say 9, 10, or 11 PM. But in a lot of people with ADHD, it's actually tuned late. So basically, the Venn diagram of ADHD diagnoses and this sleep disorder, delayed phase sleep disorder, there's actually a ton of overlap. And I do want to be clear, I am not at any point in this video saying that ADHD doesn't exist. I'm saying basically, in psychiatry, everything is based on behavioral observations. It's not like you're getting a blood sugar test and testing for diabetes. It's just observational and behavioral, so we make diagnoses that are necessarily fluffy and loose. And sleep deprivation and true neurodivergent ADHD, which is real, can look very similar, even getting mistaken for one another. In fact, in true ADHD, sleep pathways are often disrupted. Reports are mixed, but some studies put delayed rhythms, delayed sleep rhythms in ADHD, as high as 80%. And this late tuning isn't just behavioral. It tracks with hard biology: reduced volume of the pineal gland, which secretes melatonin, abnormal clock genes, and generally a melatonin rhythm that comes online late. Now, think about what happens when you drop a late clock into a world that was built around 7 AM. A person whose biology wants to sleep at 2 AM but is forced to wake up at 7 AM is living in permanent jet lag, and the result is 3 cataclysmic words: chronic sleep debt.
I am insomnia.
And chronic sleep debt produces exactly the items that are on the ADHD checklist: inattention, distractibility, impulsivity, and trouble regulating emotions. There's even a clean story for the emotional piece. Losing sleep weakens the grip that your prefrontal cortex normally keeps on your amygdala, which is the brain's threat and emotion center. So basically, when you've had poor sleep, the brakes come off the amygdala, and small frustrations become big ones. Neurobiologically speaking, it's like a dinner bell becoming a blaring fire alarm. And if you've ever watched an exhausted child, or honestly an exhausted adult, melt down over nothing, you've seen this brain circuit in action. Take a sleep-deprived child to the grocery store and tell them they can't have their favorite junk food, then watch what happens. Aaaaaah! Or, take a sleep-deprived adult and drop them in bumper-to-bumper rush-hour traffic and watch what happens. In other words, when you're sleep-deprived, the tantrum circuitry in your brain gets the volume turned up, whether you're 4 or 40 or 80. But that brings us to what I think is the best part of this video. So pay attention. We are going to resolve our paradoxes from earlier using the knowledge we've now gained together. Recall the first paradox, the inverted U, which describes how while low performers improve when they take stimulants, high performers do not improve or even do worse on stimulants. There's a principle here called the Yerkes-Dodson relationship that describes how performance with increased arousal— not attention, arousal— improves to a peak, and then falls off as arousal keeps rising. Effectively, there's a Goldilocks zone for arousal when it comes to cognitive performance. In practice, this means that people who start out under-aroused— maybe you've had poor sleep, you're generally inattentive, or those with genuine ADHD— they get pushed up towards the peak of arousal and they improve. This applies with stimulants, be they prescription or just coffee. But by contrast, when people are already sitting at the arousal Goldilocks zone, their optimum, taking a stimulant will shove them past into a jittery mode. They overshoot and they actually perform worse. Now, if stimulants were actually working by upgrading attention, this makes no sense. An improvement in attention should lift everyone and certainly not harm the performance of anyone. However, If the lever is arousal, not attention, this is exactly the pattern you'd predict because the drug's effects depend entirely on where you start on this Yerkes-Dodson curve. If you're low arousal, you get pushed to the peak. If you're already there, you get pushed over, you're jittery, and your performance tanks. That is paradox 1 resolved, but now on to paradox 2, which I love even more. This is the stimulant for hyperactivity paradox because why would we use a stimulant to treat hyperactivity? Like I said before, that's like prescribing 3 shots of espresso as a sleep aid. It doesn't make sense. But the answer is again hiding in this study. Stimulants aren't increasing attention. They're increasing arousal, yes, but recall they do one more thing. They increase what's known as task salience. In other words, they make a task intrinsically, inwardly more rewarding. Bigger dopamine hit. So imagine this: confront your brain with some mundane chore, and it logs a verdict: this is boring, there's no dopamine here. It then feels compelled to move on to something else. But if you're able to raise the reward on that task— whether it's math homework or a long, carefully worded email to your boss— and you boost the persistence on that effort, that improves what looks like attention, But is really just the intrinsic reward of the task. So what we're calling a stimulant is just persuading your brain neurochemically that the task is worth doing. And as a really interesting sidebar, this is also why some people with true ADHD have paradoxical responses to caffeine. It can appear to calm them. And you now understand why. It's thought that caffeine temporarily raises dopamine levels to make a task, the task at hand, More rewarding. So people appear to be more focused because they are more motivated to attend to that task. So the big picture here is whether you're sleep deprived or you have ADHD, the core issue might not be a true deficit in attention, but that your brain isn't getting the appropriate dopamine hit for the task, and so it goes seeking dopamine elsewhere indefinitely as you scroll through Instagram or TikTok or finally decide it's time to learn origami off YouTube. Whatever. The solution, therefore, is incredibly boring, but also incredibly effective. Get better sleep. This recalibrates the brain's dopamine and reward systems so those routine tasks give us the right hit of dopamine and we stay locked in until the job is done. And as a reflection, and a little bit of a flex, I did graduate valedictorian in college, and here's my secret. Unlike many of my peers, I never once used a stimulant or study drug. Not once. My secret was simply that I went to bed at 9:30 PM most nights. Sincerely, I was not the smartest person in my class by brute IQ. I just took care of my brain, my body, and my sleep. That's my boring secret to performance. But that brings us to something more specific in part 5, Tools You Can Use. Because if a misaligned clock is generating these symptoms, then the solution is obvious. Drag the clock Earlier, and you should relieve the symptoms. This tends to work in the studies we have, and the tools for shifting a delayed clock are unglamorous but established and effective. First, bright light early in the day, ideally real sunlight as soon as you wake and not through a window. This is the strongest signal we have for pulling a delayed clock earlier. Second, guard the other end of the day. Starting 90 minutes before your target bedtime, cut out bright blue heavy light. This is what your clock reads as still daytime, and blue-blocking glasses can actually help here because they filter out the light wavelengths that the cells in your eyes that communicate with your clock, your SCN, are most responsive to. Third, you need to anchor your whole sleep system on a fixed wake time even on weekends. Because if you swap sleep schedules between the week and the weekend, it's kind of like circadian whiplash. It's jarring to the system. And fourth, you can use melatonin to help move your cycle earlier, but there's one nuance I do have to underline because almost everybody gets it wrong. Melatonin used to shift a clock is different than melatonin used as a sedative. You don't need a megadose. You need a small dose, say 1 milligram, taken several hours before your target bedtime. This is a decent timing signal, helping to nudge your clock earlier in the day. Having said all that, there are some more advanced tools that I discuss and provide access to in the associated letter, which goes with this article and is linked below. And if you aren't already subscribed to the Stay Curious Metabolism newsletter as well, please consider doing that because it's another great way to support me and what we do here on this channel. But now let's bring this all back to the vignette from the beginning of the video. Those days where ADHD or not, you just can't focus and it is so frustrating. But now, now that I'm aware of these data, I find a nearly perfect correlation between the days that I'm sleep deprived and the days when I just can't lock in and focus. Maybe construction woke me up. Maybe I got in bed late because I was jet lagged from traveling, or perhaps I was just delinquent and stayed up watching House of the Dragon season three finale. Whatever the reason, I now notice that when my sleep is impaired, I just can't focus the next day. And in retrospect, that relationship is intuitive. It is obvious. But I now understand why, and now hopefully. You do too, because what might be happening in my brain, and perhaps yours too, is something that might actually mimic ADHD. And the solution, therefore, at least for most of us, is not necessarily to get a prescription stimulant, but to be aware of this possibility and use it as motivation to clean up your sleep hygiene. Because I don't know about you, but for me, 95% of the time, sacrificing productivity just isn't worth it, no matter how good the season finale is. But I will reserve that 5%.
