The effect of benzodiazepines is quite profound. They work, according to a 2012 New York Magazine article, by "suppress[ing] the output of neurotransmitters that interpret fear". In other words, they eliminate our ability to feel danger, which to someone with a panic disorder may mean the abatement of an anxiety attack. Or, for someone who's taken four times the recommended dosage and mixed that with alcohol, could mean the beginnings of something much more catastrophic.

It's been this way since the 1960s, when doctors in America first started prescribing benzos. And through their various guises over the years – Valium, Klonopin, Xanax, etc – they've become one of the most controversial drugs in medicine; yes, they work, but at what cost?

Benzo abuse can be seen most starkly in the US, where over 5 percent of the adult population takes them, and where an estimated 10 to 25 percent of longtime users are dependent. This parallels with about 9,000 benzo-related deaths in 2015 and, since 2000, a 500 percent increase in the overdose death rate. Benzos are particularly lethal when combined with opioids, accounting for about 8,000 of these deaths, and in around a third of all fatal overdoses some form of benzo is found. The reason for this is the depressive effect benzos have on the central nervous system: they limit our breathing and heart rate as a result of the suppressed neurotransmitters, leaving the body ultra vulnerable to other substances.

Elvis, Heath Ledger, Michael Jackson, Amy Winehouse and Whitney Houston all had benzos in their systems when they died, yet it's unemployed white men between the ages of 18 and 34, who are addicted to another substance, who are the likeliest to abuse the drugs. There are two explanations here: one, their "softening" effect when coming down from something else; two, their cheapness, with benzos in the UK going for around £1 or £2 on the street. Up and down the country, people use benzos to help bring them down after all-nighters on whatever other drugs they've chosen to put inside themselves.

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The extent of benzo abuse right now is evident on Reddit's "Drugs" forum, which has become infested with what the locals call "bartard" stories, referring to a "bar" of Xanax – meaning an entire tablet, two to four times an effective dose for anxiety. These stories are written half as cautionary tales and half as boasts, with many common elements: the poster takes what he assumes is a reasonable amount, before waking up hours or days later with a trail of destruction in his wake and no memory either of having caused it or of taking way more than planned.

I reached out to "CzerwonyMan", the guy responsible for the most popular bartard story on Reddit. He's an 18-year-old American who was institutionalised having been picked up by police following a Xanax blackout. The difference between benzo blackouts and alcohol-related ones is that, rather than fall asleep, a user with a decent tolerance can continue to function. "Benzos are very good at making you feel a lot less fucked up than you already are," he told me, "so you tell yourself to take another when you're already off your ass high. My benzo use was purely recreational to start, but even after the first few days of messing with benzos there's just this mental pull towards doing them. Knowing that you can if you want to is all that it takes to chew another bar."

The community at Reddit has also coined another term, "Xanman", to describe the optimum state of benzo intoxication, where one isn't blacking out but existing in some kind of buzzy flow state where only good things happen. It's evident, of course, reading the Xanman stories why anyone would want to use benzos recreationally – however, their number is so small in comparison to the bartard stories that it's difficult to see Xanman as anything other than an aberration; some brief stop on an inevitable road to ruin.

I asked CzerwonyMan how long he'd been using before ending up in the psychiatric hospital. His answer surprised me: "My use only spanned over the better part of a few weeks, but I was using every single day."

And why benzos? "All of my drug use started by being curious about what different drugs feel like. With the obviously-growing reputation of benzos, and Xanax in particular, I just wanted to try them. But tolerance built pretty quick, and soon it starts to take triple what it took at first to get you where you want to be. Being sober was the last thing I wanted because I liked the feeling of Xanax so much, so I was pretty much on it 24 hours a day."

"I decided to stop [taking benzos] completely. It was about two weeks after that I experienced PAWS [post-acute-withdrawal syndrome] for the next two months. It hit me with the worst period of mental illness I've ever had, and I just wasn't expecting it."

The reputation of benzos is growing in the UK, too. Though the abuse isn't on the level of the US, 366 people were killed by benzo-related overdoses in 2015 – more than by cocaine, speed or MDMA. Somewhat surprising is that obtaining a prescription on the NHS is virtually impossible unless you're attending a drug detox or clinic, or have been on them for a very long time – from back when their prescriptions were written more freely. The NHS' opinion is that the withdrawals and addictiveness aren't worth it; thus people are left to turn to the streets, or darknet, to get them.

The darknet scene right now is particularly interesting. About five months ago, around the time bartard stories began getting popular, talk on the "Darknet Market UK" Reddit switched from low-frequency chatter about a variety of benzos to relentless posts about mainly one: Xanax. DNMUK is a busy forum full of vendor ads and customer reviews, where the public interaction between buyers and sellers contributes to, one hopes, a greater level of safety on the darknet. Basically, customers review the drugs they receive in the post based on a number of categories – service, shipping, stealth, security and communication – and scam vendor are quickly rooted out.

The Xanax market is naturally complex. Xanax is made from alprazolam powder, which is concocted in labs and sold on the darknet from Britain as well as countries like China, Portugal and Canada. The price varies depending on order size, but usually a gram is about 60 US dollars: enough to make 500 2mg bars.

The powder is then pressed using machines and binding agents; often, what you buy on the darknet aren't legitimate pharmacy-found pills. Until June of 2017 this was done almost exclusively in Britain by "UKBenzos", a former vendor who'd graduated solely to manufacturing, and distributed by "HulkedBenzoBoss", another vendor who by then dealt only in large quantities. Their lower-level vendors were "imperialstormtrooper" and "SmokersDelightUK", who sold mainly to smaller-time users.

Then, a month ago, HulkedBenzoBoss went missing, and with no way of contacting UKBenzos directly, imperialstormtrooper, SmokersDelightUK and the UK darknet were running out of Xanax. The reason for the ensuing panic was simple: withdrawals. The effects of going off benzos cold turkey (as opposed to tapering) are legendary in their awfulness. They include trembling, nausea, seizures and psychosis.

I spoke to a former benzo user who'd gone through cold turkey, who agreed to speak on the condition of anonymity. "To help me sleep, I started taking them daily during the week," he said. "I was aware it wasn't a good idea, so started using them more occasionally. This carried on for about two years. I decided to stop completely, as this was going well. It was about two weeks after that I experienced PAWS [post-acute-withdrawal syndrome] for the next two months. It hit me with the worst period of mental illness I've ever had, and I just wasn't expecting it. Two months is a very long time to go through something like that with no light at the end of the tunnel. I'm very lucky to have such a compassionate boss or I wouldn't have kept my job."

"Being sober was the last thing I wanted because I liked the feeling of Xanax so much, so I was pretty much on it 24 hours a day."

In the days follow the disappearance of HulkedBenzoBoss, a new vendor appeared on the darknet. He claimed to be "behind the infamous UKBenzos brand" and instructed everyone to now order Xanax through him. Because no one knew what had happened to HulkedBenzoBoss there was understandable suspicion that this new vendor was part of a police sting triggered by his arrest. Even imperialstormtrooper and SmokersDelightUK neglected to do business.

However, within the first week the vendor still received orders for 15,000 bars, and with everyone now having received the same pills UKBenzos was producing, suspicion that he's police has mostly abated.

One can't help but wonder, though: to what extent are people dependent if they're willing to order off someone so suspicious, and to what extent can someone take advantage of this in future? Right now, the vendor is selling 100 bars for around £50, but what incentive does he have to keep the same price; and what incentive does the next guy have – when this vendor inevitably disappears – to sell safe products?

Why all of this is happening right now – from bartards in the US to Xanax-obsessed darknet buyers in the UK – is undoubtedly a combination of factors: hype, easy availability and price. At a time when young adults are ravaged with anxiety about their place in the world, it's obviously appealing for those on both sides of the Atlantic to get fucked up in a way that's super cheap and super effective. However, to say this has gone too far would be an understatement. Genuinely, there seems to be no ending to this story other than an unhappy one.

I ask CzerwonyMan what his thoughts were as he was locked inside the hospital. "I was just filled with huge amounts of regret," he told me. "'How could I let something like benzos get me put into the loony bin?' was basically what I asked myself for the eight days in there. It felt like one small stupid decision had a huge impact on my life – that'd mess up everything I'd worked for previously."

He continued: "It may seem like your life's alright with some benzo use, but only until you stop using them will you really see how fucked up you've actually gotten yourself."