ADHD and the brain

Researchers have learned a lot about the ADHD brain through studies that use brain imaging. They’ve been able to identify differences in brain structure and function in parts of the brain that control executive function. Most ADHD symptoms are problems with attention and the brain’s “braking” system, called inhibitory control.opens in a new tab

Here’s what we know about ADHD and the brain.

Research shows that parts of the brain are smaller in kids with ADHDopens in a new tab than they are in neurotypical kids, including the prefrontal cortex. This region of the brain plays a key role in attention, inhibition, and overall executive control.

By young adulthood, these brain structures tend to be similar in size to those in adults without ADHD. But problems with how the brain communicates, called network connectivity, continue. While symptoms of ADHD may change over time, ADHD is lifelong for most people.

Brain structures need to work together to do things like shift focus or read or write. Different parts of the brain are connected by networks of neurons (brain cells).

Some neural networks take longer to develop or may be less efficient in kids with ADHD. One example is the “default mode network.” This network plays a key role in resting the brain.

In kids with ADHD, the brain takes longer to “switch off” activity in the default mode network when they need to focus on something. Research shows that changes in this network may also cause problems with social functioning.opens in a new tab (Many people with ADHD have social difficulties because of impulsivity and trouble picking up on social cues.)

ADHD affects other pathways too, like the frontoparietal network. It plays a key role in making decisions and learning new tasks. (That’s why it’s often called the “executive control circuit.”) Differences in this and other neural networks may help explain ADHD symptoms like mind-wandering and trouble with impulse control. 

Brain networks are made up of brain cells that pass information along from neuron to neuron. To do this, the tail end of one neuron releases tiny amounts of chemicals called neurotransmitters. These chemicals have to cross a small gap — called a synapse — to get to the tip of the next neuron.

ADHD can affect this process in a few ways:

• The sending neuron may not release enough neurotransmitters.

• The receiving neuron may have trouble “catching” the neurotransmitters.

• The neurotransmitters may get sucked back up by the sending neuron too fast, before a good connection is made with the receiving neuron.

For many people, ADHD medication can improve these connections. Tapping into people’s interests can also help.

Brain researchers are learning more and more about ADHD. But we haven’t yet reached the point where brain scans can be used to diagnose people with ADHD. Learn how kids are evaluated for ADHD, and how it’s diagnosed in adults.