L-Theanine Was Called a Focus Factor. What Did the Study Find?

What did the 2026 study test?

The post is by Dr. James M. Greenblatt, on his Psychology Today blog. He calls the 2026 study “randomized, double-blind, placebo-controlled.” He writes that L-theanine with caffeine “helped slow a decline in reaction time during an attention task.” He adds that it “also decreased ‘false alarms’ (responses to irrelevant stimuli).”

The study ran in the journal Nutritional Neuroscience. The lead author is Gayani Nawarathna, who teaches physiology at the University of Peradeniya. The team studied 21 young people with ADHD, 18 boys and 3 girls.

Each one came in on three separate days. One day, they took L-theanine mixed with caffeine. Another day, they took a placebo, a dummy dose with nothing active in it. On the third day, they took the ADHD medicine they already used, for comparison. Neither the young people nor the researchers knew which dose was which. We leave medicine out of this post. That choice belongs to a family and their doctor.

The task was simple. Triangles flashed on a screen. Press for the ones pointing down. Ignore the ones pointing up. Each person did the task before the dose and again 50 minutes after.

Is L-theanine a “focus factor”?

PsyPost covered the study in August 2026. Here is what it reported for the combination, compared with the placebo. There were fewer false alarms, or presses for the wrong triangle. There was less slowing down as the task went on. And one EEG signal came sooner. EEG reads brain waves through the scalp.

Those are real results. They are also smaller than “focus factor” sounds.

Here is what the combination did not do. It did not clearly speed up average reaction time. In study terms, that change was not significant. On hitting the right triangles, the mix did no better than the placebo. PsyPost explains why. Nearly everyone scored near the top. The task was too easy to show a difference.

Two more limits matter. The study gave one dose, on one day, in a lab. PsyPost notes it was only big enough to catch large effects. Whether any of this shows up in class was not tested.

And look at the caffeine. The study tested L-theanine and caffeine together. It did not test L-theanine on its own. An earlier 2020 study did test it alone, in five boys. Its own title calls it a proof of concept.

So here is the frame we hold. A small, careful study found a few narrow changes in a lab. That is worth knowing. It is not the same as a focus factor.

What does this mean for your child?

We are not telling you to use L-theanine or to skip it. Thinking about any supplement or caffeine for your child? Ask your child’s doctor first. The post also gives Dr. Greenblatt’s own dosing advice for sleep. He says it comes from his clinical practice. The 2026 study did not test it.

The bigger question is what focus runs on. Our view is that attention sits on top of several things. When focus is hard, we look at more than focus. Sleep, hearing, vision, worry, mood and learning all get a look.

The CDC says this on its page about diagnosing ADHD:

“There is no single test to diagnose ADHD, and many other problems, such as sleep disorders, anxiety, depression, and certain types of learning disabilities, can also have symptoms similar to ADHD.”

The American Academy of Pediatrics wrote an ADHD guideline for doctors in 2019. It is the latest AAP guideline on ADHD we found. We could not confirm it is still in force. It says the evaluation should “at least screen for comorbid conditions.” Its examples include anxiety, depression, learning and language problems, and sleep apnea.

Worth checking is not the same as likely. Neither source gives a rate for how often another problem is the real cause. We hold none either.

There is a tradeoff. A supplement feels quick. Checking sleep, hearing and worry takes longer. But it gives you a fuller picture of your child. For more, read our guide Attention Difficulty vs ADHD: What Parents Should Understand. It covers who makes the diagnosis and what else to check.