The US state Oregon, legalised assisted dying in 1997, for terminally ill adults with six months or less to live.
It is also legal in California, Colorado, Hawaii, Maine, Montana, New Mexico, New Jersey, Vermont, Washington and Washington D.C. And some other states are considering legalising it.
Switzerland has allowed assisted suicide for adults since 1942 and its Dignitas facility began operating in 1998.
Assisted dying is legal in Canada for terminally ill adults, but the country has delayed an expansion to its medical assistance in dying programme for people who have a mental illness.
Some countries have made it legal for teenagers to take their own lives, in certain circumstances.
The Netherlands, external, for example, has legalised assisted suicide and euthanasia. Minors can request it starting at the age of 12, but need parental consent until they are 16.