At least 172 people have taken their own lives using the suicide powder “substance X”  since 2015, suicide prevention organisation Stichting 113 and the Amsterdam health board estimate.

It is the first time an investigation has been carried out into how widespread use of the powder is, the organisations say.

The average age of people who had obtained the powder was 59, although the biggest group, some 38%, was over 70.

“The figures show that this is a very diverse group. It’s not only made up of elderly people who have made a considered choice,” researcher Lizanne Schweren told the NRC.

The investigation also showed the use of substance X increased five-fold between 2017 and 2021, from 10 to 50. The following year, 42 people used the powder to kill themselves.

Based on autopsy reports, the researchers found that 120 people had a “psychiatric record”, which included in some cases depression or anxiety. Some 19 had requested euthanasia in the prescribed way but over half had been rejected.

The unnamed powder is used in the chemical industry and when ingested it can take up to 40 hours to die. Selling the powder is not an offence in itself unless the purpose is to help someone take their own life. Under Dutch law, it is illegal to help someone to die, unless a doctor acts under the strict terms of euthanasia legislation.

Seven people aged between 70 and 80 are currently standing trial on charges of forming a criminal organisation and supplying the suicide powder.

All seven are either members or former members of the right to die group Cooperative Last Will, which believes everyone has the right to end their lives at the time of their choosing and has long campaigned for an end-of-life pill.

The results of the investigation had been known since January but have only been published now. “Communication about suicide methods brings the risk of copy cat behaviour, but the reporting of the court case said no figures were available, and we wanted to set the record straight.” Schweren told the paper.

Anyone struggling with suicidal thoughts can talk or chat anonymously with the helpline 113.nl or call the free number 0800-0113.