ADHD

Currently, about 10% of 6- to 11-year-olds and 14% of 12-to 17-year-olds in the US have been diagnosed with ADHD. Worldwide, the figures are closer to 5% of children. Whatever numbers you look at, there are a lot of adults and children diagnosed with ADHD.

Everyone has their pet theory on the increase in ADHD - it's the food additives, too much sugar, video games / TV rotting the brain, lead in the pipes, pesticides, prenatal exposure to something, overdiagnosis, etc...

My updated article on ADHD looks at the topic from a genetic perspective, exploring the pathways connected to genetic variants that increase the relative risk of ADHD.

Studies show that there is a strong genetic basis (70-90% heritability), but it is not just one gene. You don't have the "ADHD Gene," even if it is fun to say :-) Instead, it's a combination of genetic variants and environmental interactions. Understanding the genetic susceptibility can lead to more targeted solutions.

This week, I updated the ADHD article and genotype report. Previously, it had focused primarily on neurotransmitter variants and circadian rhythm variants.

What was missing from the article was the well-researched role of the gut microbiome and the gut-brain axis connections.

Here are four things you may find surprising about ADHD:

1. ADHD looks more like a circadian disorder than most people realize:

Up to 73–80% of people with ADHD have measurable circadian rhythm disruptions, including altered expression of core clock genes like PER2, BMAL1, and PER3, along with shifted cortisol and melatonin rhythms.

In adults with ADHD, combining morning bright light with just 0.5 mg melatonin at night shifted melatonin onset almost two hours earlier and cut symptom scores by about 14%. Important here is that symptoms rebounded when melatonin was stopped.

This also means that blue light from screens and LED lights has a bigger impact than most people understand, or want to admit, when it comes to their ADHD symptoms. (Here's how to shift your iPhone to red at night.)

2. The gut can literally “transfer” ADHD‑like behavior in animal models:

Children with ADHD have distinct microbiomes, including higher Prevotella and reductions in short‑chain–fatty‑acid producers. Several studies now link this to lower microbial vitamin B12 synthesis and altered inflammation, which affects the gut-brain axis.

In a cool study, when researchers transplanted a low‑Lactobacillus sanfranciscensis microbiome from kids with ADHD into mice, the mice developed hyperactivity and inattention. What made the study neat is that those behaviour changes could be reversed with probiotics or with supplemental acetate (a short‑chain fatty acid).

3. Histamine genes tie together eczema, food dyes, and ADHD:

Allergy-adjacent conditions like eczema, allergic rhinitis, and asthma are significantly more common in kids with ADHD, pointing toward overlapping inflammatory and histamine pathways.

A common variant in the histamine‑degrading enzyme gene HNMT (rs1050891) is linked both to higher brain histamine and to hyperactivity triggered specifically by artificial food dyes, making low‑histamine, dye‑free diets a targeted strategy for people with HNMT variants.

4. Saffron supplements rival methylphenidate (Ritalin) in trials:

Multiple clinical trials in children and adults report that 20–30 mg/day of saffron can be as effective as methylphenidate for ADHD symptoms, both by boosting dopamine, serotonin, and norepinephrine signaling and by affecting the gut microbiome.

While these are four distinct pathways, they all intertwine... histamine can be produced in the gut microbiome; saffron can increase short-chain fatty acid producing bacteria; the gut microbiome can influence circadian rhythm - and vice-versa. All of these then interact with the brain and neurotransmitter homeostasis.

The goal of using your genetic data in ADHD is to give you a starting point. For example, if you have a bunch of circadian rhythm variants, start with changing your light exposure (no blue light at night, lots of daylight in the morning). If you have histamine or gut-related variants, start with the lifehacks that are linked to those topics.