Can You Actually Have Too Much Dopamine?

Dopamine. You hear about it all the time when it comes to ADHD. The story we’ve all heard is that as ADHDers, we have dopamine deficient brains and that we must do things to increase our dopamine OR ELSE. 

But how true is this really? Do we really need more dopamine? Is low dopamine the true cause of ADHD, or are there other things going on? Should we be constantly focusing on increasing our dopamine? And is it possible to have too much dopamine? 

I’m going to be breaking that all down for you today, because, guess what? There’s a lot of misinformation out there, and I want you to know the facts so you can understand the science behind what’s really going on and make the right decisions to make your life easier so you can do the to-dos and have some fun along the way too. 

So the reason I decided to do this blog is because I hear a similar thing very frequently from ADHDers.

It will go something like, “I find myself doing XYZ for the dopamine.”

So to give you some examples I will hear:
–I find myself eating sugar at the end of the day for the dopamine
–I was low on dopamine so I wound up playing with my phone for hours
–My low dopamine causes me to make impulse purchases that I later regret

And I can’t blame people for saying this. All over the internet is tons of advice about dopamine detox, dopamine menus, dopamine boosting supplements, this that and the other. 

So let’s figure this out, shall we? 

I found a great review that was published in Frontiers in Psychiatry that examined evidence we have so far after studying dopamine for decades. Their conclusion is that, no, there does not appear to be much evidence that low dopamine is a main driver of ADHD. Let me say that again if you missed it. There is not much evidence to suggest that our ADHD is coming from this chronic state of low dopamine! 

The review really combed through the literature to date on dopamine and ADHD and here are some of its main points. 

They pointed out that there are some studies with animals that show changes in genes related to dopamine and these animals do exhibit ADHD-like behaviors such as hyperactivity and inattention. So, one point for team dopamine deficiency, right?

Well, not so fast, because if you look deeper into these animal models, you will also see that there is a correlation between issues with other genes that aren’t directly related to dopamine. For example in these animal models we can see ADHD-like behavior in mice, where the mice have had certain other genes modified not really related to dopamine, including a gene that affects how we experience pain, inflammation levels, and even how fast food moves through our guts.

And there’s another mouse model where scientists alter a gene related to thyroid function and kablowey! you get a mouse that behaves in a very ADHD way. So, those two examples in animals point out that there’s probably more to the story. It’s not simply low dopamine equals ADHD, because if it were just a dopamine thing, changing other things wouldn’t do anything.

Now I know at least one person is out there going, “but those are rodents! What about people?!”

Well, scientists have been trying to crack the genetic code on ADHD for decades, looking for a specific gene that would explain everything. Early on, they thought they had found it in a gene called DRD4, as some research suggested that a specific type of variant in this gene seemed to show up more often in people with ADHD, but with larger and more rigorous studies, the link started falling apart, womp womp. 

Researchers looked at other dopamine-related genes like DAT1, COMT, and DBH. When they looked at these genes, a few promising results, hey maybe we’ve found it and then nope, same thing, nothing really consistent to show a genetic issue with dopamine and ADHD being strongly linked.

Now as time has gone on as it does and technology has improved as it tends to do, scientists have done even more studies to analyze genes and they still haven’t found strong evidence for dopamine-related genes to be linked to ADHD at all. [1]

“Well,” you might say, “maybe it’s not that there’s a problem with dopamine-related genes but that the environment is causing low dopamine and that’s what’s going on,” and that’s a valid thought but it doesn’t hold up to scrutiny either. That same scientific paper points out that there are some environmental and developmental factors that have been shown to be related to ADHD, but they affect more systems than just dopamine. So attributing everything to dopamine? That just ain’t it.

Here’s something else mentioned in the paper which I found fascinating which is that there are clear conditions where there is indeed a clear low level of dopamine and so if the idea that ADHD is just low dopamine, anyone with these conditions should automatically have ADHD, right? Well by now you can probably guess where I’m going with this because you are a smart cookie.

For example, to make dopamine, the main way that we do it is through a two-step process that involves two different enzymes plus some cofactors. Let’s not get too much into the weeds today and let’s just leave it at this, the first enzyme in this process is called “tyrosine hydroxylase” which takes the amino acid tyrosine and boop! sticks another molecule onto it to make it into L-DOPA which then goes through another boop! with another enzyme and we get dopamine. 

This enzyme tyrosine hydroxylase is considered a rate-limiting step in the making of dopamine, meaning if ya ain’t got enough of it, you’re going to have low dopamine, end of story. 

So that gives us another way to explore whether or not low dopamine is really the cause of ADHD, because if we need this enzyme, let’s call it TH for short, to make the bulk of our dopamine, and low dopamine is the true cause of ADHD, then anyone with low TH should have ADHD, amirite?

So what do you think the studies have shown? I bet you can guess!

When we look at people who have TH deficiency then leading to mild to severe dopamine deficiency, what we mainly see are what the paper refers to as “movement symptoms.” And here we’re not talking about things like fidgeting like we can see in ADHD but rather actual difficulty moving, a kind of stiffness of the muscles and also involuntary muscle contractions. If you’re thinking that this sounds like Parkinson’s you’d be right. More on that later!

So here we have a clear population of humans with low dopamine and instead of all having ADHD what they mainly have are serious issues with being able to move their bodies how they want to. [2]

Now what happens when we look at brain scans and let me pause here just to say that if you yourself are considering getting your brain scanned to tell you if you have ADHD or not just don’t. The evidence base for that being of any use as a diagnostic tool at this moment in time is pretty much nil. 

But let’s look at the evidence that’s out there about brain scans as we continue our dopamine deep dive. What do the scans say about us, are we dopamine deficient or dripping in the stuff?

The paper looked at results from both PET and SPECT imaging and the results were mixed mixed and more mixed. A 1999 study found lower dopamine levels in the midbrain of ADHD kids but after doing statistical corrections the numbers didn’t hold up.

Meanwhile other studies have shown no difference in dopamine function and several actually suggest a hyperdopaminergic state in ADHD, did somebody say hyper? Meaning that there’s evidence that there might actually be too much dopamine bopping around in there. In a minute I’m also going to talk about what happens when that is the case, meaning what happens when we have too much dopamine. Is it bad? Stay tuned!

So the brain scan studies really do not support the theory that there is a dopamine deficiency when it comes to ADHD. [3]

But one thing the brain scans DO support is that there is a higher incidence of a brain energy issue in ADHD, specifically prefrontal glucose hypo-metabolism. What does that mean? This part of the brain here right behind your forehead, if you have ADHD, is more likely to be bad at using sugar. The sugar is there but it’s not getting taken up into the brain as much as it should be, especially in the part of the brain that does what? Helps with attention, decision-making, goal-setting, self-control, working memory, and even understanding feelings. [4] 

These can all be areas that ADHDers really struggle with, or so I have heard. 

Never happened to me a day in my life! Of course I am kidding.

And so that’s one possible way therapies like ketogenic diets can help calm ADHD symptoms because it gives our brains an alternate fuel source to use - ketone bodies. So we can use some glucose and some of the ketone bodies and the brain just seems to work better. That’s definitely what happened to me and I wouldn’t give up this feeling for all the sour gummy worms in the world. 

The paper also discusses another potential mechanism behind ADHD which is an issue with neurovascular coupling. Now what the heck is that? No it’s not two med school students hooking up on their lunch break, but rather the link between blood flow and brain activity. Very long story short, it looks like in ADHD, some parts of the brain are getting less blood flow than they should and some are getting more. So this is yet another possible explanation behind what’s causing ADHD that is not just “not enough dopamine.” [5]
  
Now all that being said, there is a different disorder that does have a lot of evidence that its sufferers do in fact have lower dopamine and that is Parkinson’s disease. So what can we learn from that? 

Well, celebrities like Ozzy Osborne (may he rest in peace) and Michael J. Fox have brought more attention to Parkinson’s so now most of us understand at least the basic idea of how it looks so I won’t go into it here. Fun fact I once nearly literally ran into Michael J. Fox at an art gallery in New York because I was walking super fast and didn’t see him. Sorry Mr. Fox I really didn’t mean to. I was distracted by all the art. Forgive me.

So now when we look at Parkinson’s, we see lots of evidence of a depletion of dopamine in Parkinson’s patients. [6]

And in fact, dopamine replacement therapy with something called Levodopa is currently the gold standard when it comes to Parkinson’s treatment. It has been used for more than 50 years and often dramatically improves motor symptoms while patients are on it although the benefits can start to poop out and many patients do develop motor complications on it after several years of use, so far from perfect, but the point is there is a “dopamine treatment” that increases dopamine levels in the brain. Now why the quotes because it’s not actual dopamine but rather a precursor. [7]  Dopamine itself doesn’t cross the blood-brain barrier so if I were to reach through the screen and inject you with dopamine right now, it wouldn’t go to your brain. That said, actual dopamine injections are used in hospitals, mainly to treat low blood pressure and slow heartbeat. [8]

Okay so you may be thinking, “Well what happens if we give Levodopa to people with ADHD?” And guess what this has been done before. Based on everything we’ve talked about so far, what do you think happened? Do you think the Levodopa helped people with their ADHD symptoms or not? Well, not. For example in one study, albeit a small one, giving Levadopa to children with ADHD was not shown to help their ADHD symptoms at all but it did seem to help improve their Restless Leg Syndrome. 

Okay so by now I’ve perhaps convinced you that ADHD is not simply a dopamine deficiency. So what? What does this mean for us in our day-to-day lives? 

Well, two main things. Number one, maybe we should stop listening all of that advice bouncing around in the echo chamber that is the Internet about ways to raise your dopamine, supplements you can take to double your dopamine, how to do a dopamine detox so that later you can blast yourself with more dopamine, music to increase dopamine, why you should make a dopamine menu of things to supercharge your dopamine, what colors to paint your house to dopamine your dopamine, the perfect spring outfit to make those dopamine levels soar, why I named my pet Doberman dopamine and you should too, etc. etc. you get my point . . . If ADHD really is not being caused by a lack of dopamine or low dopamine levels or a dopamine deficiency . . . what the heck are we doing trying to chase more dopamine? It’s a misguided obsession if you ask me. It’s a dangerous oversimplification. I’ve seen people in my practice when they first come to me they’re taking supplements because someone online told them it would raise their dopamine or as I mentioned in the beginning they’re explaining everything through this dopamine lens, like, “I have to eat chocolate while I’m studying for the dopamine . . .” Hmm, maybe not. 

Number two, you can actually have too much dopamine. Wait, what? Let me say that again you can actually have too much dopamine!

So let’s start with an extreme example. Remember how we were just talking about Parkinson’s and how there are medications that increase dopamine levels? Well, as it turns out, there are reports of people having some pretty scary side effects from some of them. Without getting too far into the weeds, there is evidence to suggest a link between these medications and the development of impulse-control disorders. This can include things like compulsive spending, problems with gambling, and even hypersexuality, whoopsies. 

Now wait a minute, you might be thinking, those are issues that many ADHDers are more likely to deal with as well, especially those with predominantly hyperactive ADHD or those like me who were diagnosed with combined type. [9]

So to reiterate this here we saw evidence to suggest that increasing dopamine levels in the brain resulted in more impulsivity. 

So, yikes, maybe time to rethink those dopamine-boosting supplements you were about to waste a bunch of money on, eh?

And speaking of money, whoa Nelly did I find a fascinating study on how higher dopamine levels could be linked to more impulsive behavior. What they did was compare the effects of a dopamine-boosting drug on placebo in terms of impulsivity and the way they did this was ask people if they wanted a small amount of money now or a large amount of money later. They asked this over and over again with different amounts of money and time and on multiple testing dates.

When the subjects had been given medication that increased their dopamine levels they more often chose the smaller but sooner reward, so think impulsive because you’re giving up more money later for the feeling of getting something quickly.

And in what the researchers called a “striking” finding, this happened in all of the participants! It wasn’t just the average! Every single person in this study, albeit a small study, chose “smaller faster” more frequently when they had more dopamine in their system. [10]

Now there is another entire angle to this that I’m not even going to scratch the surface of in this video, but just to put it on your radar, in the future I hope to put out some content about how certain overgrowths in the gut microbiome show a strong correlation to many mental health issues, the proposed mechanism behind this being that they are impairing the breakdown of dopamine to epinephrine a.k.a. adrenaline and that this is causing a landscape of too much dopamine compared to downstream neurotransmitters and that this pattern is seen often in ADHD, autism, schizophrenia, and many other conditions. Make sure you’re subscribed to this channel so that you don’t miss that when I make it, it’s going to be a doozy. 

So there you have it. ADHD is much more than just a dopamine deficiency. In fact, it looks like it’s not a dopamine deficiency at all! 

And honestly? It kind of makes me mad. Because we've all heard this shouted from the rooftops with such certainty like it was settled science, a done deal, like, “Of course it's a dopamine deficiency! What else could it possibly be?” But, looks like it’s not, and hearing things like that makes me want to question everything I’ve learned about ADHD, which is why I'm going to keep doing just that! 

Thanks so much for being here, and have a happy and healthy day.