ADHD and Serotonin: A Missing Piece?

ADHD and Serotonin: A Missing Piece?

Most people know that ADHD is linked to problems in the brain’s neurotransmitter systems—especially dopamine and norepinephrine. But one piece that often gets overlooked is serotonin.

Research from biochemistry, genetics, and pharmacology suggests that serotonin transmission doesn’t work quite the way it should in people with ADHD. In fact, many studies point to an overall shortage of serotonin availability in the brain.

This review digs into how serotonin is made and used in the body, focusing on possible weak spots in the process. For example, converting tryptophan (an amino acid found in food) into 5-hydroxytryptophan (5-HTP) requires certain chemical helpers—like the cofactor tetrahydrobiopterin. If any part of this chain is disrupted, serotonin levels can drop.

Why does this matter? Because these steps could open the door to new treatment possibilities. By better understanding how serotonin pathways function in ADHD, researchers may be able to target these areas for future therapies.

Extra Insight

Serotonin isn’t just the “feel-good” chemical—it also influences impulse control, emotional balance, and even how well we manage stress. These are areas where many people with ADHD struggle daily. If serotonin pathways really do play a bigger role than we’ve been giving them credit for, then treatments aimed at improving serotonin function could help with parts of ADHD that stimulants don’t always address, such as mood regulation, sleep, or irritability.

It’s also worth noting that lifestyle factors—like diet, exercise, and sleep—directly affect serotonin levels. While medication research is still catching up, this connection suggests that supporting serotonin naturally might give people with ADHD an extra tool to manage symptoms. It’s not a “cure,” but it highlights how ADHD is a whole-brain condition that involves much more than just dopamine.

Jackson EF, Riley TB, Overton PG. Serotonin dysfunction in ADHD. J Neurodev Disord. 2025 Apr 22;17(1):20. doi: 10.1186/s11689-025-09610-y. PMID: 40264019; PMCID: PMC12013068.