Troubled by his parents' divorce and often left home alone as a teen, Nelson Cook started drinking with a group of older boys at the age of 12.

The next year, he tried cannabis and, at age 15, psychedelics. It was the start of a lifelong struggle with addiction.

Mr Cook, who grew up in Helsinki and is now 46, told The Straits Times that looking back, he recalls receiving drug education as a student. "I remember a policeman saying he knows of users who ruined their mental health because of drugs. The warnings didn't sink in."

He was sent to the countryside to live with his relatives at age 19, and in his 30s, underwent treatment in St Petersburg, Russia. But his addiction - to heroin, by that time - proved difficult to kick.

"I was so obsessive, I couldn't think about anything else," he said.

For most of his life, Mr Cook took drug after drug - when the side effects of one became too severe. He moved from job to job as well, and found himself unable to maintain stable relationships.

"All I knew was, I was very paranoid and anxious. I was still an untreated addict. At a later age, when I was with doctors, I realised I had paranoid schizophrenia."

It was only about six years ago that Mr Cook became determined to quit drugs: "I was so fed up with being a walking pharmacy."

Besides taking medication, which he got from treatment centres, and attending recovery programmes, he started seeking help through Narcotics Anonymous and Alcoholics Anonymous.

While he relapses with alcohol at times, he has since sworn off drugs.

His strongest message is directed at parents.

He said: "I'd like to tell parents, it's important to get a child into a safe home. Most of the people I know from recovery have had an insecure childhood."

Seow Bei Yi