"Hong Kong is climbing up there when you consider the majority of the population is not Western in Hong Kong. That's quite a high percentage," said Alastair Mordey, programme director at The Cabin.

A small number of young Chinese with ketamine addictions make up the rest of The Cabin's Hong Kong patients.

Mordey says the new clinic will allow high-functioning addicts, such as bankers, to fit treatment in around their careers.

"The concession that you make as an outpatient service is that you're on their doorstep," Mordey said. "It's their business to rejig their evening meetings to save their life."

Treatment in Hong Kong will cost US$6,000 for six weeks, or US$10,000 for a 12-week programme of group and individual counselling sessions and meditation. Up to 20 people will be able to take part in group counselling sessions at the clinic. One month at The Cabin in Chiang Mai, where the rooms feature four-poster beds, costs US$12,900.

Addiction is an illness that appears in adolescence, Mordey said, adding that most addicts encountered substance abuse issues in their early twenties.

"[They're] probably starting to move towards risky behaviours in their twenties, which would include their careers: sports person, rock climber, banker, criminal."

Poor dopamine function in an addict's brain, or the ability to absorb the reward chemical, causes symptoms of irritability, restlessness and extreme boredom, which Mordey describes as the primary illness.

Addicts seek out risk or use sex, drugs, alcohol or gambling to self-medicate and boost dopamine levels in the brain.

Researchers have found links between certain genes and addiction, suggesting people have a predisposition to addiction.

A series of anonymous confessionals by bankers in Hong Kong has highlighted the sometimes hedonistic nature of their profession and expatriate life in the city.

Around 80 per cent of expatriate addicts The Cabin treats are male and their professions range from banker to teacher.

Mordey said expatriate life in an alien culture could lead to excessive drinking. "They stick to their own and it's what expatriates do, and it's been the same since the British Raj right up: they drink a lot," he said.

However, Mordey said a person's job was not to blame for their excess.

"There are people with addiction issues that will make their way into certain careers; it's not the other way around," Mordey said. "It's not the cultures that create the drug use."

Most of the addict bankers seeking treatment at The Cabin are middle managers and a small number are referred by their company's human resources department. "In reality it's the HR departments that get involved directly where they have a high-net-worth individual," he said. "It doesn't make sense to hire and fire. They want to keep that resource that they've invested years in."

In recent years, banks have started to place greater importance on employees' mental health and this aspect is now included in health examinations, a banking source said.

Staff can access mental health support anonymously through external agencies, known as employee assistance programmes, the source added.

Joanne Schmitt, an addiction counsellor at The Support System who has worked in the field in Hong Kong since 2008, said clients had told her that drugs such as cocaine were cheaper and more easily available in the city than elsewhere.

"When someone does begin to use, or if they're at all susceptible to addiction, that ease of availability can make it quite difficult then to stop," Schmitt said.

On Wednesday, airport customs officers seized a 5.4kg consignment of cocaine with an estimated street value of HK$5.5 million, which authorities said was destined for the local market.

In the first nine months of this year, 60.7kg of cocaine was seized at Chek Lap Kok airport in 27 smuggling attempts.

In the same period last year, 110kg of cocaine was seized from 33 smuggling attempts.

There were also fewer barriers to drug taking for expatriates in Hong Kong, Schmitt said.

"Partly I believe it's because we're away from our families," she said. "There's more time and space for that and many of us don't drive, so that again takes away another barrier.

"Even professions where we may not think of it as a typically heavy drinking profession, they will say that in Hong Kong it is very much part of the work culture to go out and party," she added.