Drugs counsellor Darren Gold, from Essex, smoked cannabis heavily for 12 years from the age of 15.
His drug use led him into a life of petty crime, filled with several periods in prison. He attributes much of what happened to him to cannabis use.
"I started smoking cannabis because I was desperately unhappy at school. I had a fantastic upbringing, and had great parents, but I was separated from all my friends when I went to secondary school, which made me lonely. Because I was going through puberty, I became even more depressed, and had very little self-confidence.
"Then I started hanging out with a group of kids who smoked and drank. When I was 15, one of my friends brought some cannabis to school. We smoked a joint, and I remember rolling around on the ground and laughing hysterically. All my problems disappeared. I wasn't worried about anything any more. It was such a relief.
"I started smoking more and more because I wanted to keep feeling good. Within a week, I was smoking cannabis practically every day. I had to steal to fund my habit, but I didn't care.
"After leaving school, I lied to my parents about getting a job, and I'd hang around with my friends, stealing cars, joyriding and smoking dope all day. Soon I started selling drugs, but I smoked more than I sold, and I was always getting in trouble with the dealers.
"I ended up spending two months at a young offenders institution. While I was there, I was attacked. When I got out, I started smoking even more cannabis, but it made me really paranoid. I kept thinking that the boys who attacked me were watching me and following me. I was constantly looking around for them.
"My mum was really worried about me, and suggested I go to Israel to live on a kibbutz for a while. Eventually I did and, at first, I thought it was great. For six months I couldn't get any drugs. But I was drinking heavily instead.
"After a while I left the kibbutz and went to live in Tel Aviv because I'd heard that you could get cannabis there. I ended up dealing again. But the paranoia started to get much worse. I was convinced the police were following me and bugging my phone. I used to live in fear of them abseiling down the building and coming in through my windows, SAS-style. I had no idea it was the cannabis making me think that.
"Eventually I was raided by the police. I was lucky because I had hardly any drugs at the time, but they still put me in jail. The conditions were terrible, but when I got out on bail, I moved to another part of the city and started dealing again.
"When my court case was due, I came back to the UK because I was afraid I was going to get a long sentence. By the time I came home, I was in a real state. I was still smoking cannabis heavily, and I was taking heroin too.
"In the end, I was arrested for burgling my parents' house and for several drug offences. Thankfully, my mum stood up in court and pleaded with the judge to send me to rehab. I was sent to a prison with a good drugs unit. If I hadn't been, I would probably be dead by now.
"I've been clean for almost nine years. I put every last bit of effort into giving up drugs, and now my life couldn't be better. I trained as a counsellor and I have a wife and a six-month-old baby. For the last four years I've been a Drugsline outreach team leader working with kids in schools and organising programmes on drugs awareness. My mum and dad are so proud of me.
"All that cannabis I smoked has left me with a bit of a temper. That's something I still have to discuss with my counsellor every now and then. The paranoia is still with me, but not to the same extent as before. But I doubt myself, even today. When I do something really good, I still tend to see the downside.
"Smoking cannabis played a huge part in what happened to me. But I don't look back at what could, should or would have been. I don't want to live in the past. I want to live for the future.
"I'll continue to work at it. I've come a long way and turned my life around, and I'm pretty happy with that."
There are several sources of help if you or someone you know has a problem with drugs. Find out more in Drugs: where to get help.