Nepal, Oct. 10 -- This article discusses suicidal behaviour. If you have questions on self-harm or feel suicidal, Nepal's national Suicide Prevention helpline is 1166. Use this link to find an international helpline.

Last year, my phone rang late at night. A colleague from a Kathmandu hospital was on the line, his voice sounded urgent. The patient was a 17-year-old boy who had ingested enough lethal pesticide to end life.

What was more shocking was not just his age, but the fact that this pesticide was banned in Nepal four years ago. On paper, it should no longer exist in the market. In reality, the banned substance is still available, sold discreetly to avoid regulators. But it is within easy reach of those in despair.

Despite the doc...