I've been drinking four cups of coffee a day since I was 7... here are the terrifying things that happened when I quit cold turkey

My head is pounding. Why is his keyboard so loud? God, her voice is annoying. Do I smell someone microwaving an entire roast chicken? Why does my head still hurt?

Experts have assured me that, no, my brain is not overheating - I’m just in the depths of caffeine withdrawal, a real clinical condition.

I've been a coffee drinker since I was seven. I believe my dependence on caffeine results from after-dinner cups of coffee diluted with mostly warm milk (Italians call it a cappuccino, have you heard of it?).

Eventually, my desire to be more sophisticated and metropolitan led me toward a habit of racing to the front of the line for a cold brew before work.

These days, I drink around four cups a day, amounting to an elephantine caffeine dose of about 390 milligrams. A small feather in my cap as national health organizations say up to 400 milligrams is safe.

So why did I quit - save for a few decaf espressos - for a full week? In short, I did it for the story.

According to Dr Ann Monis, a clinical psychologist, I have what could be classified as caffeine use disorder.

This explains why I've failed at past attempts to cut down, and why I keep reaching for another cup even though I know anything beyond the third is lubricant for a panic attack.

I set the rules for myself the week before last: Starting Saturday afternoon, no coffee, energy drinks or tea. I did allow myself the caffeine in chocolate - I'm not perfect.

Once I started the trial, I indulged in some decaf espresso when the afternoon doldrums hit. One coworker pointed out early on that this might be cheating since decaf still usually contains small amounts of caffeine.

If it is, it’s the lamest form of cheating possible, especially given that I'd been in a stupor and jonesing simultaneously.

Yes, I was still able to do my job. But a fogginess hung in my head, draping my mind in a thick haze.

I was expecting my lack of coffee to affect the way I felt and thought but not to the extent that it did.

Caffeine blocks adenosine, a compound that tells your brain it’s time to rest.

Take it away, and adenosine surges, leaving you wiped out and struggling to manage even simple tasks.

‘Mood changes are part of the withdrawal process, too,’ Dr Monis told me.

‘Without that daily [dopamine] stimulation, many people experience a drop in drive, low energy and a kind of emotional flatness.

'Irritability is common and, in some cases, depressive symptoms can surface… Some even report a spike in anxiety, not because caffeine was calming them but because their body was depending on that familiar chemical rhythm to stay balanced.’

Writing a single sentence without caffeine in my bloodstream sometimes felt like running in the opposite direction on a moving sidewalk in the airport. I got to the other end eventually, but my heart was beating faster, my thighs kind of hurt and I felt like an idiot for going backward.

My phone’s Notes app is chaos - a side effect of my anxious, fast-moving thoughts bouncing from one idea to the next.

For example, Monday’s entries included: ‘Teared up at my desk, Luke [my colleague] says I look pale (rich coming from him).’

Wednesday: ‘I feel bionic – like wires and rods are attached to my bones, making me glide like I’m on ice’, followed by, ‘I need to find a cone of soft-serve ice cream yesterday’, and punctuated by, ‘I want my face on gold coins.’

Thursday’s was simple: ‘Heavy sigh.’

That same day, Dr Monis told me, 'You’re on day five, which lands right within the peak period of withdrawal. Most people experience the strongest symptoms between days two and seven.'

A large share of coffee drinkers have made attempts to cut down. A 2012 study found that 62% of 275 people attempted to cut caffeine - and 62% of them couldn’t stay off it for a full month.

Forty-three percent said they had been told by a health professional to drink less to improve or reduce the risk of heart disorders, anxiety, headaches, urinary problems, gastric problems, high blood sugar and sleep disorders.

During my own trial period, I noticed a more troubling side effect than what was in my rogue notes: more pronounced involuntary arm and hand movements that I sometimes get as a result of a daily medication I take.

The side effect is known as dystonia, a movement disorder linked to abnormal signaling of the neurotransmitter dopamine.

According to Dr Monis, caffeine blocks adenosine receptors, ramping up brain activity, including in motor regions.

Over time, the body adapts by producing more adenosine receptors and tweaking dopamine (key for movement control). Quit caffeine abruptly, and the system backfires - adenosine surges, dopamine drops and motor pathways get jumbled.

'For someone already experiencing involuntary muscle activity, that disruption may make movements more noticeable or harder to manage,' Dr Monis said.

The basal ganglia - critical for smooth movement - in the neocortex of the brain are dopamine-sensitive. Dystonia often stems from glitches here.

'And since caffeine mildly boosts dopamine activity, especially in these areas, cutting it off abruptly could create a temporary reduction in motor control stability,' she said.

'That does not mean caffeine was treating the dystonia directly but it may have been masking or moderating some of its effects. Without it, the baseline shifts and symptoms can temporarily flare up.'

The jerking motions my arms make as the muscles contract are sudden and unnerving at the best of times, but they became almost cartoonishly grand.

Nicola Noél, a registered specialist mental health nurse and founder of Brain Works Therapy, told me, 'You’re effectively removing a daily modulator, so your nervous system may be temporarily more excitable or dysregulated.'

I've wondered many times why I volunteered to do this experiment on myself.

Was it worth it?

My withdrawal symptoms - now with tremors - still haven’t eased. Employing decaf coffee and chocolate are like putting Band-Aids on a bullet wound.

No one tracks how many Americans have caffeine use disorder but studies suggest that 8 to 35 percent might qualify.

‘The length and intensity of withdrawal vary depending on how much caffeine a person was consuming and how long they’ve been using it consistently,' Dr Monis said.

'Most symptoms peak between 24 and 72 hours after stopping but, for some, it may take a full week before they feel like their mind and body are leveling out again.’

'Very cool. Very, very cool,' I whispered to myself, sinking deeper into my chair with images of the cold brew I would inhale at the very first opportunity flitting through my head.

The week without my precious cold brews, cappuccinos, doppio espressos and all the other pretentious coffee drinks I hate to love was - if I’m being demure - trying. If I'm being honest, it was cataclysmic.

Either way, thankfully, it did come to an end.

The following morning, I went to a cafe nearby, and bought a much-longed-for cold brew. Large. Skim milk.

The first sip was on par with a psychedelic experience. I felt a bit dizzy but only temporarily. From there, it was as though a rush of good chemicals hit my brain. Colors were brighter, sounds were sharper.

And I vowed to my blessed coffee: never again.