Could L-Theanine Save the World? (Or At Least the ND Nervous System)

Burnout & Energy
Written by Hannah Anstee

Dear fellow neurodivergent woman,

It was just after sunrise and I was sitting on my patio doing absolutely nothing other than sipping a glass of iced water. My body had stopped rushing. Slow, but not tired. No racing thoughts, no circulating to-do list, no extra energy with nowhere to go. I’d done my morning chores at half speed, mindfully, noticing the gentle sound of tap water flowing into the sink as I prepared the washing up. My bare feet padding along the tiled marble floor. Cockerels crowing in a neighbour’s garden. Then I meandered outside to water my plants and pick off any brown leaves. It was beautiful.

How had I reached this state of blissfulness? I’d taken 200mg of L-theanine.

L-theanine, which is an amino acid found in green tea, came onto my radar last year. My friend, a doctor in DC, mentioned a protocol for PMDD that some of her patients were having success with, and L-theanine was one part of that protocol.

I don’t have PMDD, but I’ve seen the misery it creates, and I’ve read studies which suggest the root cause is the same as so many other conditions commonly associated with neurodivergence — CFS, POTS, fibromyalgia — dysfunctional mitochondria.

L-theanine is known for promoting calm focus: it crosses the blood-brain barrier to increase alpha brain waves and boost calming neurotransmitters like GABA.

That piqued my interest, because in the past, after long fasts — 24, 48 hours, not something I’d recommend for anyone with a chronic illness, but it’s what I was doing (in ignorance) — I’d feel unbelievable, like a holy spiritual being, completely at peace. Turns out that calm comes from an intense release of GABA.

I wanted to know, as always, how it affected the mitochondria. The research was positive: L-theanine acts as a mitochondrial protector, enhancing cellular energy production, preserving mitochondrial structure, and defending against oxidative stress.

But the real gold was in the Reddit comments. People use L-theanine to reduce stress and social anxiety without drowsiness, boost cognitive function, mitigate caffeine jitters, and improve sleep. More specifically, autistic and ADHD users described it easing social anxiety, reducing sensory overstimulation, and improving focus without sedation. One user described walking into social situations without anxiety for the first time, and starting to go to the gym regularly off the back of it.

That stopped me in my tracks. Regular readers know that sensory overstimulation is the biggest ongoing cost of my life.

Quick caveat before I go any further: I’m a qualified metabolic health coach, not a doctor, and recommending supplements is outside my scope of practice. This is just my own experience and what the research says. If you’re on blood pressure medication or sedatives, please talk to your doctor before you try this, not after, as L-theanine can amplify both.

So L-theanine was now no longer something I was just interested in overall it was something I wanted to try for myself.

I bought a little plastic bottle of vegan capsules at my local pharmacy for $30. A usual dose seems to be 100–400mg a day, split across two doses. 100mg did nothing. The next day, 200mg. That’s the moment I opened with.

After that, the obvious next question was whether something that felt this good could become addictive. I get attached to things easily. But the research said L-theanine wasn’t addictive or habit-forming: it doesn’t trigger the brain’s reward centres the way addictive substances do, and there’s no withdrawal and this has been my experience too.

Why not just drink the tea? Because a cup only gives you about 60mg, which is not enough for a real dose. One popular use is pairing it with strong coffee: it takes the edge off caffeine jitters and tips you into a sharp, hyper-focused state. I’ve used this for big pieces of computer-based work that require a lot of executive function, and it works.

I never intended to take it daily. I didn’t feel like I needed to, and anyway, apparently you build tolerance easily and then it stops working. I used it for potentially stressful social situations: markets, supermarkets, crowds. Or when I needed to focus on a big task. So maybe 2–3 doses a week, sometimes less.

I checked it against my thyroid medication and HRT: no interactions.

I was so won over that I recommended it to three women close to me — not as a coach, just family and friends. All three came back saying it worked exactly as described. One now takes 200mg before every weekly team meeting.

Another interesting piece is that it regulates your nervous system while you’re on it, but when it wears off, you’re left with a nicely tuned system purring along, instead of crashing straight back into dysregulation, the way ADHD brains chasing a dopamine fix often do.

Over time, I noticed I was becoming more regulated generally. Traffic didn’t bother me as much. I didn’t always need earplugs. Social interactions stopped feeling like getting punched in the stomach.

It made me think about my 20s and 30s in the UK — antidepressants, a 9-to-5, trying to be a “normal” mum — and how useful this would have been then.

During my research I also found out that L-theanine is widely used in the ME/CFS community for anxiety, insomnia, and brain fog, without drowsiness.

So why does nobody talk about it? Even now? Taylor Swift takes it for anxiety, half of Silicon Valley apparently uses it for focus, Reddit has thousands of comments on it. And I’d never heard of it.

The honest answer is there’s no large-scale human trial data proving long-term safety and efficacy, and there’s probably never going to be, because pharmaceutical companies can’t make big money off green tea.

There are real interactions worth knowing — it can amplify blood pressure medication and sedatives, and may lower blood pressure too much for people with hypertension. But plenty of medications interact with other things, and that alone shouldn’t rule out large scale trials.

It’s not a magic fix. I still come home overstimulated on hard days. But it’s a genuine buffer, and often I forget to take it simply because I feel good enough to forget I need it.

The second time I used L-theanine was for something completely different. After a bout of dengue when I first arrived in Cambodia, my mast cells became highly reactive to food, heat, and dust. This was all made worse by an already-restrictive keto diet, and by the fact that sweltering heat and dust-filled roads are just life here.

My neck came up in huge red welts — rough, raised, sometimes looking like they were about to bleed. Plus huge, momentous hot flushes ripping through my body like it was on fire, which would send me into a panic.

But I wasn’t willing to restrict my diet further or leave Cambodia, so I turned to the method that had worked for my chronic fatigue: Dr. Sarno’s mind-body approach. Retraining my brain with one practice being reading aloud daily statements rejecting the idea that these triggers were dangerous — that they were due to emotional overload and a dysregulated nervous system — while deliberately doing the triggering things anyway, to retrain the nervous system out of a false alarm.

It’s a kind of wild approach: eating parmesan and spinach and soy sauce, knowing they will likely cause a huge trigger and distress. But when you’ve healed yourself before by ignoring what mainstream medical advice tells you, and then achieved complete recovery, you have a lot of faith and courage to do things your own way — or at least Dr. Sarno’s way.

This practice worked almost immediately, until — true to form — I stopped doing it. As the symptoms had vanished I didn’t feel like I needed to anymore, and there were so many other important things to be doing, such as, oh I dunno, going for a swim, meeting a friend for coffee, reading a dystopian novel in my hammock. The symptoms came back.

This is EXACTLY what happened with my CFS recovery, btw. You think you’re better, but actually you haven’t rewired the neural pathways strongly enough, and you’re more vulnerable to relapse than you think.

So I got back to it, and this time, I added L-theanine into the mix.

Turns out it’s also a mast cell stabiliser: it inhibits mast cell degranulation and the release of histamine and inflammatory cytokines, and buffers the stress response that triggers inappropriate mast cell activation in the first place.

I took it twice a day, on a fixed schedule, even after I built a tolerance and stopped feeling its effects directly. The protocol said it kept working on the nervous system regardless. After two weeks I saw a significant improvement, and within one month, the mast cell activation had fully resolved.

I believe this worked so quickly because of two things. While I was reading my daily reminders, I was far more present, and able to digest the statements slowly and thoughtfully. And, of course, the science behind L-theanine and mast cell stabilisation.

Somewhere in the middle of all this, I texted my doctor friend:

I feel like L-theanine could change the world? 🤔 If everyone was on it…

She replied:

Hahaha. I COMPLETELY agree!

Picture our world leaders dosing up on calm and bliss instead of cortisol and ego. Probably less division. More watching plants growing slowly.

And for an ND nervous system specifically — one that’s been masking and bracing through sensory overload for years — L-theanine doesn’t fix anything. But it does give you a bit more room to breathe in your own body, and what a miracle that can feel like, some days.

If sensory overload and crashes are your thing, you might also like Why You Crash After a Good Day and Why Your Unfelt Emotions Are Draining Your Energy.

I hope you have a blissful week,

Love Hannah xoxo

The practical bits — dosing, safety, what to flag with your doctor — are already above. This is just the research behind it, for anyone who wants the receipts.

The Science, In Brief

What it is

  • A non-protein amino acid found mainly in green and black tea, and in some mushrooms

  • A cup of tea contains roughly 20–60mg; supplements typically run 100–400mg per dose

How it calms you

  • Crosses the blood-brain barrier

  • Increases alpha brain wave activity — the “calm but alert” state

  • Boosts GABA, the brain’s main calming neurotransmitter

  • Doesn’t cause drowsiness, unlike most sedatives or anti-anxiety medication

Mitochondria and energy

Mast cells and histamine

  • Identified as a mast cell stabiliser in a landmark 2011 study (Kim et al., Amino Acids)

  • Inhibits mast cell degranulation and the release of histamine and inflammatory cytokines

  • Buffers the stress response that can trigger inappropriate mast cell activation

Addiction and safety

  • Not considered addictive or habit-forming; no known withdrawal

  • Doesn’t trigger the brain’s reward pathways the way addictive substances do

  • Can amplify the effects of blood pressure medication and sedatives

  • May lower blood pressure too much in people with hypertension

  • Talk to your doctor before starting it, especially if you’re on any medication

The catch

  • No large-scale, long-term human clinical trials yet — most research is in cell and animal models, or small human studies

  • Widely used in ME/CFS, autism, and ADHD communities for anxiety, sensory overstimulation, sleep, and brain fog — but that’s community and anecdotal evidence, not clinical proof

Sources

Hannah Anstee
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