I Thought Caffeine Was Helping Me Think

For a long time, I thought caffeine was helping me function.

Coffee helped me wake up. Tea helped me work. Caffeine gave me that little push that made starting something easier.

Eventually, I realised something uncomfortable:

I had confused stimulation with functioning.

I have ADHD and I am autistic, and I have spent years using caffeine as a way of changing the state of my brain.

I do not remember exactly when it became a regular part of my life. It was somewhere between two and four years ago. What I do remember is that there was a period when coffee became almost impossible to separate from my daily life.

I was drinking it constantly.

And I was not calm.

I was anxious. I was rushing. I was constantly anticipating something. I had episodes that felt like panic attacks. My stomach would hurt. My sleep was disturbed. I was making decisions from a state of constant activation.

At the same time, I was saying yes to too many things.

I was people-pleasing.

I was entering relationships that I probably would have approached differently if I had been thinking from a calmer state.

I was constantly trying to solve things immediately.

Everything felt urgent.

At the time, I did not understand the connection.

I just thought that was what being productive felt like.

The strange thing about caffeine

Caffeine does not actually give your brain energy in the way we usually describe it.

One of its primary actions is blocking adenosine receptors. Adenosine is involved in the accumulation of sleep pressure and the regulation of wakefulness. By blocking adenosine signalling, caffeine makes you feel less sleepy and more alert. It also affects several other signalling systems involved in arousal and motivation.

That distinction matters.

Caffeine can make you feel more capable of doing something without necessarily making the underlying conditions for good thinking better.

You can be more awake without being more regulated.

You can be more activated without being more focused.

You can be more productive without being calmer.

And I think this distinction is particularly interesting when we talk about ADHD and autism.

Not because autistic or ADHD people should never consume caffeine.

The evidence does not support that claim.

But because both ADHD and autism are associated with sleep difficulties, while caffeine itself can interfere with sleep. Adults with ADHD and autistic adults both show, on average, poorer sleep characteristics than control groups in systematic reviews and meta-analyses.

That creates a potentially important loop:

poor sleep → caffeine → temporary alertness → disrupted sleep → more caffeine → dependence on stimulation → repeat.

And you might not even recognise that you are inside the loop.

I thought I needed stimulation

This was probably the biggest thing I misunderstood.

I thought caffeine was helping me overcome my ADHD.

And there is a reason that idea can feel convincing.

Caffeine is a stimulant. ADHD medications can also be stimulants. There is research investigating caffeine’s effects on ADHD symptoms, including a systematic review of randomised trials in children, but that evidence is nowhere near strong enough to establish caffeine as an ADHD treatment.

The subjective experience can still be compelling.

You drink caffeine.

You become more alert.

You start working.

Your attention seems to lock onto something.

You think:

This is what my brain needed.

But there is another possibility:

Your brain needed less sleepiness, while your nervous system needed less stimulation.

Those are not the same thing.

I think this distinction became obvious to me only after I stopped.

The calm was the strange part

When I finally stopped relying on caffeine, something unexpected happened.

The world became quieter.

Not literally.

Internally.

I could sit with a thought for longer.

I did not feel like everything needed to happen immediately.

I was less interested in responding to every stimulus.

I could think before acting.

And I started noticing how much of my previous life had been lived in a kind of permanent urgency.

That is difficult to explain because caffeine does not necessarily make everyone anxious.

Some people can drink coffee and feel completely fine.

The FDA, for example, notes that up to around 400 mg of caffeine per day is generally not associated with negative effects for most healthy adults, although sensitivity varies considerably between people.

That is important.

This is not an argument that coffee is poison.

It is an argument about individual response.

A 2024 meta-analysis involving healthy participants found that caffeine intake was associated with increased anxiety, with larger effects at higher doses. A 2026 systematic review similarly found evidence of a dose-dependent relationship between caffeine and anxiety, while noting differences between individuals and habitual users.

My experience was extreme enough that I eventually stopped asking:

“How much caffeine is safe?”

and started asking:

“What does caffeine do to me?”

Those are completely different questions.

The sleep problem is bigger than I realised

The most interesting part of this is probably sleep.

Caffeine can remain physiologically relevant long after you stop feeling its obvious effects.

A systematic review and meta-analysis of controlled trials found that caffeine reduced total sleep time, reduced sleep efficiency, increased the time required to fall asleep and reduced deep sleep. One analysis estimated that a standard coffee would need to be consumed roughly nine hours before bedtime to avoid a measurable reduction in total sleep time.

That is remarkable.

You do not have to drink coffee immediately before bed for it to matter.

You can drink it in the afternoon, feel completely normal by bedtime, fall asleep, and still have your sleep affected.

And this matters because sleep is not a minor side effect.

If your sleep is consistently worse, you are changing the conditions under which your brain has to regulate attention, emotion, memory and arousal the next day.

For someone already struggling with attention regulation, that can become particularly relevant.

Then there is dependence

Another thing I underestimated was how normal caffeine dependence can become.

Caffeine withdrawal is a recognised clinical phenomenon. Symptoms can include headache, fatigue, drowsiness, irritability and mood changes. Research suggests withdrawal can begin within roughly 12–24 hours after stopping and may last several days.

That means something strange can happen with habitual caffeine use.

You drink caffeine because it makes you feel better.

Eventually, part of the reason you feel better may simply be that you are reversing the withdrawal state produced by not having it.

So the cycle becomes:

caffeine → adaptation → withdrawal → caffeine → relief.

Research has found that some regular caffeine users meet proposed criteria for clinically meaningful caffeine dependence, although the prevalence and clinical significance remain debated.

That was exactly the part that felt familiar to me.

I was not simply enjoying coffee.

I had reached a point where stopping felt difficult.

And when something becomes difficult to stop even after you have noticed that it is causing problems, it is worth questioning the relationship you have with it.

Why I am particularly interested in ADHD and autism

I want to be careful here.

There is not enough evidence for me to say:

“Caffeine is bad for autistic people.”

There is not enough evidence for me to say:

“Caffeine is bad for people with ADHD.”

Those statements are too broad.

Autism and ADHD are not single physiological states. People experience them differently, have different sleep patterns, different anxiety profiles, different medications, different metabolisms and different sensitivities to stimulants.

But there is a more interesting question.

What happens when you take a psychoactive stimulant and introduce it into a brain that is already struggling with regulation?

That question deserves more attention.

Adults with ADHD and autistic adults both show substantial sleep difficulties in the research literature. Autistic adults also show elevated rates of anxiety, with systematic reviews finding anxiety to be a particularly common co-occurring difficulty.

Meanwhile, caffeine can increase physiological arousal, worsen anxiety in some people and interfere with sleep.

There is no need to assume that autism or ADHD causes someone to respond badly to caffeine.

The interaction is enough to investigate.

The dopamine rush was part of the trap

There was another thing I had to admit to myself.

I liked the feeling.

I liked the rush.

I liked feeling activated.

I liked the sensation that I could suddenly do everything.

And eventually, I started working from that state.

That is probably the part I understand best now.

I had trained myself to associate activation with action.

If I was stimulated, I worked.

If I was under pressure, I moved.

If something felt urgent, I responded.

If someone needed something, I said yes.

If I was tired, I stimulated myself again.

Calmness started to feel like inactivity.

That was the real problem.

Because good thinking does not always feel exciting.

Sometimes good thinking feels boring.

Sometimes it feels slow.

Sometimes it feels like sitting in silence long enough for your brain to actually finish a thought.

I had spent so much time trying to increase my activation that I had forgotten what it felt like to simply be regulated.

I do not think everyone needs to quit caffeine

This is where I think conversations about caffeine usually become unnecessarily simplistic.

One person drinks coffee every morning and feels perfectly fine.

Another person drinks one cup and becomes anxious.

Another person can drink coffee at 10 pm and sleep normally.

Someone else drinks it at 2 pm and sleeps badly.

Caffeine sensitivity varies between people, and factors including genetics, habitual consumption, medications and individual physiology can affect the response.

So I am not interested in telling everyone to stop drinking coffee.

I am interested in asking people to notice what it is actually doing.

Does it make you more focused?

Or merely more activated?

Does it improve your work?

Or does it make you rush through it?

Does it help you sleep less?

Or does it quietly make your sleep worse?

Does it make you calmer and more capable?

Or does it make you feel like everything is urgent?

And most importantly:

Can you stop?

Because that question tells you something that the number of cups you drink might not.

I stopped, and I like my brain better this way

For me, the answer became obvious after I stopped.

I did not suddenly become a different person.

I became less rushed.

And that gave me something I had not realised I was missing:

space.

Space between stimulus and response.

Space between thought and action.

Space to notice when something was a bad idea.

Space to say no.

Space to sleep.

Space to think.

Space to exist without constantly trying to increase my own activation.

I used to think caffeine was helping me get more out of my brain.

Now I wonder whether I was sometimes asking my brain to do too much while simultaneously making it harder for the brain to settle.

That distinction has changed how I think about productivity.

I do not want to spend the rest of my life needing to be stimulated before I can function.

I would rather learn what my brain feels like when it is allowed to operate without constantly pushing it.

For me, that means staying away from caffeine.

Not because caffeine is universally bad.

Not because autistic or ADHD people are incapable of drinking coffee.

And not because everyone needs to follow what worked for me.

I stopped because I finally realised something:

I did not need more stimulation.

I needed to know what my mind felt like without it.