A teenager who became a paranoid recluse after years of smoking cannabis has lifted the lid on the dangers of the drug.

Craig - not his real name - shared his first joint with his older brother when he was just 11 and has spent all of his teenage years stealing and scraping cash together to fund his spiralling habit.

Today the 19-year-old reveals how the drug turned him from an everyday pupil to a thieving dope dealer - and then to the edge of madness.

And he tells how:

  • a dealer persuaded him to sell drugs in the playground
  • teachers failed to offer him help - even though he was obviously high in lessons
  • the drug left him so paranoid he was scared to leave his bedroom
  • he was driven to steal from fellow pupils to buy his next batch.

Craig, who has now quit drugs after a month-long treatment programme at The Priory Hospital in Hove, spoke out in the hope of preventing other youngsters slipping into the horror he faced.

The then 11-year-old had just started secondary school when he shared his first joint with his older brother.

He started smoking every day, dealing to his school friends and stealing mobile phones in exchange for cannabis.

At 16 he dropped out of college and for the next two years he barely left his bedroom, too scared to venture further than his dealer's doorstep.

His drug use began with him smoking cannabis resin - known as hash - at a friend's house after school while his parents were out at work.

Soon he started bunking classes and hanging out with other pupils in a graveyard near the school in Worthing.

His friends would also meet at a council flat belonging to an older friend, who would supply them with cannabis.

They later met a dealer who encouraged them to sell cannabis to friends at school in order to fund their habit.

Craig said: "I would take an ounce of cannabis to school in my pocket each morning, sell half of it, then leave when I had enough money.

"We were also stealing mobile phones from people's bags which we could swop for an ounce."

Although one friend was expelled after being found smoking a joint, no-one else Craig knew was ever caught by teachers, despite the scale of the problem.

He said: "By Year 11 pretty everyone I knew had smoked it.

"I was a renowned stoner at school - I was always the lazy one with bloodshot eyes. It must have been obvious but I was never offered counselling at school, which could have helped me."

Although he started smoking hash, he found he could not get stoned fast enough so moved on to the more potent skunk cannabis, which is home-grown under hydroponic lights to produce more of the mind-altering THC compound.

Although he managed to pass some GSCEs, he later dropped out of college and stayed in his bedroom at his mother's house all day.

He said: "I became quite depressed and had terrible insomnia. I smoked constantly - from first thing in the morning to last thing at night.

"I owed money to a lot of people and became really paranoid. I had delusions. I thought people were talking about me and was always looking over my shoulder.

"My mum had smoked a little bit of hash all her life but she didn't really understand. She's from the hippie generation and always thought cannabis was harmless."

Craig started drinking heavily - half a bottle of spirits and a couple of cans of lager a day - and began to lose touch with his friends. His two-year relationship with his girlfriend also collapsed.

Help eventually came when he sought psychological help to deal with abuse he had suffered as a teenager. He was told he must deal with his drug and alcohol problems first and with financial help from his family he checked in for the £16,000 Priory programme, which lasts for a year.

He said: "My personal view is that cannabis is fine in moderation, but daily use can be very damaging for some people."

Craig's story highlights mounting evidence which links frequent cannabis use with mental illness.

This week a collaborative study published by Cardiff University found that individuals who had used cannabis were 41 per cent more likely to suffer psychosis than those who had never used it.

The project, funded by the Department of Health, found the risk was relative to dose, with the most frequent users more than twice as likely to have a psychotic outcome.

Dr Stanley Zammit, who led the study, said around 14 per cent of young adults who have had psychotic episodes would not have suffered them if they had avoided cannabis.

He said: "Despite the inevitable uncertainty, policymakers need to provide the public with advice about this widely used drug.

"We believe there is now enough evidence to inform people that using cannabis could increase their risk of developing a psychotic illness later in life."

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