Suicide tourism in Switzerland is apparently now a booming industry. According to multiple reports, the tourists taking part in the suicide tourism in Switzerland have doubled since the year 2009.

According to Reuters, foreigners traveling to Switzerland to take part in assisted suicide, a practice prohibited in many countries, has doubled over a four-year period. The findings have been published in a study in the Journal of Medical Ethics on Thursday.

In 2012, there are already 172 foreigners who visited for the suicide tourism in Switzerland. That is reportedly double the number from 2009 which is 86 tourists, who took their lives in the country.

Switzerland has liberal euthanasia rules.

According to the study, citizens who took most part of the suicide tourism in Switzerland are from Germany and Britain, making up almost two-thirds of the total number.

NBC News reports that according to Dr. Saskia Gauthier of the Institute of Legal Medicine at the University of Zurich in the Journal of Medical Ethics, many of those who took part in the suicide tourism in Switzerland are those from countries with strict laws that do not allow voluntary assisted death.

Gauthier wrote, "While assisted suicide is strictly restricted in many countries, it is not clearly regulated by law in Switzerland. This imbalance leads to an influx of people -'suicide tourists'-coming to Switzerland."

In his study, Gauthier was able to identify 611 cases of people who ranged from the ages 23 to 97, coming to Switzerland to plan their deaths assisted by "right to die" groups such as Dignitas.

The study has detailed that there are currently four right-to-die organisations in Switzerland, allowing foreign visitors to choose and make use of their services, taking part in the suicide tourism in Switzerland.

According to the news agency Agence France-Presse (AFP), this kind of tourism is completely unique to Switzerland.

From 2008 to 2012, records have shown that 611 foreigners from 31 different countries in the world had chosen to come to Switzerland as "suicide tourists."

A press statement said, "Their ages ranged from 23 to 97, with the average being 69," and apparently, nearly 60 percent of these people taking part in the suicide tourism in Switzerland are women.

Reuters reports that assisted suicide has been legal in Switzerland since the 1940s. The act only needs to be performed by someone with no direct interest in the other person's death.

In the Netherlands, "mercy killing" is also reported to be legal, as well as Luxembourg, Belgium and some U.S. states. However, it is still illegal in many parts of the world. This has resulted to terminally ill people to travel abroad and seek for the service without their loved ones or doctors becoming prosecuted.

The AFP reports that most deaths assisted by the suicide tourism in Switzerland were helped by the drug sodium pentobarbital, also known as the "peaceful pill".

In 2008, four people reportedly inhaled helium. However, the media said these deaths were "excruciating". Researchers said this could have been the reason for the decline in visitors from 123 in 2008 to 86 in 2009.

Meanwhile, courts in Britain, France and the European Court of Human Rights have reportedly been at odds with the suicide tourism in Switzerland in recent months.

During the previous year, according to the AFP, the ECHR urged Switzerland to clarify their guidelines. Apparently, an octogenarian who wanted to end her life has failed to convince doctors to assist her because her condition isn't enough for her to be described as terminally.

Reuters reports that the decisive factors to be considered a candidate for the suicide tourism in Switzerland are neurological conditions such as paralysis, motor neuron disease, Parkinson's and multiple sclerosis.

Because of the rise of tourists taking part in the assisted suicides, heated debate arose in Switzerland, UK, France, among others.

2011 has brought voters in the canton of Zurich to reject proposed bans on assisted suicide and "suicide tourism." However, the following year, the national parliament reportedly voted against tightening controls on the practice.

Though there has been a rise in the suicide tourism in Switzerland, few countries still takes part in the practice. Helping someone end their life is still a punishable crime in many parts of the world, even if they are suffering severe and incurable pain.

The study's authors said that assisted suicide is not clearly regulated by law in Switzerland.

South Africa's Nobel Peace laureate, archbishop emeritus Desmond Tutu said last month that he supports assisted dying for the terminally ill.

An analysis of the 611 cases between 2008 and 2012 found that the people who took part in assisted suicide in Switzerland consisted of the following:

Nearly half from Germany with 268, 20 percent British from the UK with 126, France with 66, Italy 44, 21 from America, 14 Austrians, 12 Canadians and eight each from Spain and Israel.

Suicide tourism in Switzerland was reportedly put to light after actor Robin Williams committed suicide last week after being diagnosed with Parkinson's disease.