ADHD is NOT caused by low dopamine

Your brain is simply a mismanaged mail service

There are a lot of half truths about ADHD that are floating around these days, and some people have built entire brands around these oversimplifications. Unfortunately, this leads to strategies built around garbage science, which isn't going to set anyone up for success. So let's get a few things straight that you might have seen repeated on social media.

• ADHD is NOT caused by low dopamine. If you truly had low dopamine throughout your body, you would lose basic skills like motor control similar to Parkinson's. As an article from Nature explains, "Collectively, the data hinted that a possible cause of ADHD was not an overall deficit of dopamine in the brain, but rather a scarcity of the molecule specifically in the synapses."

• Dopamine is NOT the "pleasure" chemical or the "happy" chemical. This misconception stems from neuroscience research that predates the 1980s. Think about it, people with ADHD aren't universally depressed, which is the effect you'd see if dopamine really was a pleasure chemical. Dopamine actually controls other things, like motivation, planning, coordinating your actions, working memory, emotional regulation, motor control, and many other skills spanning many parts of the brain.

• ADHD is NOT caused by trauma. This unfortunate misconception has even been spread by some therapists, but it's not true. It sets people up for false expectations that you can "cure" ADHD if you treat the underlying trauma. Although trauma can exacerbate ADHD symptoms, ADHD is about 80% heritable, putting it in a similar range as other classic genetic traits like your eye color.

The Brain is a Mail Delivery Service

To truly understand ADHD, first we need to understand some fundamentals about how the brain works. To do this, we can think of it like a mail delivery service.

Letters = Neurotransmitters The brain uses chemicals called neurotransmitters to send messages from one part of the brain to another, just like the name "Neuro" + "Transmitter" would suggest. You can imagine this like writing instructions on a note. For example, your eyes see a glass of water, so now your brain needs to instruct your hand to grab the glass and your mouth to take a drink, in that order.
Mail Routes = Neural Circuits The mail delivery routes are similar to the various pathways in the brain that the messages are being sent down. These pathways allow different parts of your brain to interact with each other, in the same way that networks of roads and highways connect cities and neighborhoods together.
Mailboxes = Receptors Once the "instructions", aka the neurotransmitters, reach their final destination, they attach to a receptor. This is like the letter being delivered to the mailbox of its intended recipient.
Junk Mail Recyclers = Transporters Your brain isn't an ordinary mail service. Yours is a boutique version with full time employees who try to filter out junk mail so it isn't cluttering mailboxes. You are eco-friendly, too, so you always recycle the paper. This is similar to transporters in the brain, which reabsorb unused neurotransmitters in a region called the synapse that don't bind to receptors. Then, it transports them away to be recycled for the future.

How are ADHD brains different?

So put yourself into the shoes of a CEO running a mail delivery service. Just like real life, your mail delivery service could run into various issues that could make your mail arrive late or never at all. At a glance, here are the key issues you might encounter:

• Paper shortage = Low neurotransmitter levels

• Broken mailboxes = Defective receptors

• Aggressive junk mail recyclers = Overactive transporters

• Slow, inefficient roads or lack of highways = Weak neural circuits

• Road construction or road closures = Dynamic network connectivity

  
  

Let's dive deeper into each of these issues and the evidence for how they contribute to ADHD traits.

Paper shortage = low neurotransmitter levels

If your service didn't have enough mail trucks, it would certainly be hard to send messages in a timely manner! You would run into all sorts of delays, if your mail even arrives at all. This is analogous to low neurotransmitter levels.

The most well known cause of ADHD in pop culture is low dopamine levels, and certainly there is compelling evidence to suggest this is part of the picture. However, the number one misconception about ADHD is that it's exclusively caused by low dopamine. As this meta review suggests, low dopamine alone cannot explain everything. For starters, we know other neurotransmitters are involved in ADHD, such as norepinephrine or serotonin.

Low norepinephrine makes sense. Dopamine can be converted to norepinephrine in the brain, so if you don't have enough dopamine, you probably won't have enough norepinephrine, either.