Germans and Britons make up the bulk of the numbers opting to come to Switzerland to end their lives through assisted suicide, while the case of one Indian 'suicide tourist' has also been recorded in 2011, according to a new study.
The study also found that the number of people travelling to Switzerland seeking assisted suicide doubled between 2009 and 2012.
While assisted suicide is strictly restricted in many countries, it is not clearly regulated by law in Switzerland, researchers said.
This imbalance leads to an influx of 'suicide tourists' coming to Switzerland, mainly to the Canton of Zurich, for the sole purpose of committing suicide, they said.
Researchers found that citizens from Germany and the UK make up the bulk of 'suicide tourists' to Switzerland, with neurological conditions, such as paralysis, motor neurone disease, Parkinson's, and multiple sclerosis, accounting for almost half of the cases.
Researchers searched the databases of the Institute of Legal Medicine in Zurich for information on investigations and post mortem examinations among non-Swiss nationals who had been helped to take their own lives between 2008 and 2012.
There are six right to die organisations in Switzerland, of which four permit nationals from other countries to use their services.
The research found that 611 people who were not from Switzerland had been helped to die between 2008 and 2012, all but four of whom had gone to the nonprofit Dignitas.
Their ages ranged from 23 to 97, with the average being 69; over half (58.5%) of the 'suicide tourists' were women, who were 40% more likely to choose assisted suicide in Switzerland than men.
Residents from 31 different countries were helped to die in Switzerland between 2008 and 2012, with German (268) and UK (126) nationals making up almost two thirds of the total.
Other countries in the top 10 included France (66), Italy (44), US (21), Austria (14), Canada (12), Spain and Israel (each with 8).
The data also reported one 'suicide tourist' from India in 2011.
The rise in the number of suicide tourists was steep in certain countries, especially Italy - up from 4 in 2009 to 22 in 2012, and France, up from 7 in 2009 to 19 in 2012.
Overall, the numbers of people being helped to die in Switzerland doubled between 2009 and 2012.
Virtually all the deaths were caused by taking sodium pentobarbital.
Four people inhaled helium - deaths which were widely publicised and described as "excruciating," and possibly responsible for the dip in numbers of suicide tourists to Switzerland between 2008 and 2009, researchers said.
The study is published in the Journal of Medical Ethics.