The family of a former school head boy who has been discovered hanged say he had been experimenting with drugs.
Matthew White was a 'wonderful boy,' says his former head teacher
Matthew White, 18, who had left St Illtyd's School in Cardiff, was found hanging from a tree after celebrating a friend's birthday in woodland.
His parents Chris and Colette White said they felt angry and bitter over his "senseless" death.
Police are investigating but said no-one else was involved in the death. An inquest has been adjourned.
Matthew's friends found his body the morning after they had spent the night in a tent in woods in the Leckwith area of Cardiff.
He had gone to sixth form college after passing 10 GCSEs, but had dropped out before his A-levels.
His parents said he had become more detached, was with a new group of friends, and told them he was smoking marijuana.
Mrs White, of Rumney, Cardiff, said he returned home less and less and began sleeping in a man-made shelter in the wood.
"I was very upset," she said. "I think I cried for about six months."
"He came home last week and spent the day with us, having a meal and going to the cinema with his brother. I was so happy to see him, it's where he belonged.
'Drifted off the rails'
"But the next morning he went with his friends and we never saw him again."
Mrs White said her son "came from a good home and he had a good upbringing. He just drifted off the rails.
"You hear about these events happening to other people, you never think it's going to be you. When he started smoking cannabis his attitude changed, there were less boundaries, but I was convinced he was coming out of it.
"But my son has lost his life and it's senseless.
"I called the National Drugs Helpline, the drugs squad and anyone else who I could phone because I felt helpless.
"Why is cannabis regarded as a soft drug? It changed my son's life."
Matthew's father said: "You go through all the emotions, anger and bitterness. You want to lash out.
"It's very hard to accept. Children should not be tempted with these drugs."
Mike Worthington, head of St Illtyd's School, said everyone who knew Matthew was devastated.
"His parents can be justifiably proud of the work he did in school and I was proud to have him as head boy.
"He was a wonderful boy, quiet, hard-working and considerate. He was chosen because of his integrity, his ability to lead and the respect he enjoyed from his fellow students."
Mr Worthington said Matthew had become "involved in a particular way of life but we all hoped he would come out of it and return to his usual self but it was not to be."
He said: "Youngsters often try drugs with the view that if they don't like it they can always pull back but it is not that easy. Once you start with drugs it takes a lot of self-determination to give them up."
The funeral is due to be held at St Cadoc's Church in Cardiff on Wednesday. Matthew's family have asked for donations to the National Drugs Helpline rather than send flowers.
An inquest has been opened and adjourned by the Cardiff coroner and adjourned pending police inquiries.