Cannabis and psychosis: Your stories
A report has warned that people who use cannabis as teenagers are increasing their risk of psychosis.
Researchers from several countries, including the Netherlands, Germany, Switzerland and the UK, tracked 1,900 people, aged between 14 and 24, over a 10-year period.
BBC News website readers from around the world have been getting in touch with their views on these latest findings linked to the controversial drug.
Dan, Bognor Regis
I have had negative effects but only when I have taken doctored cannabis”
You will find that any data supposedly "proving" that cannabis use leads to schizophrenia or psychosis are of the "cherry picked" variety.
The prohibitionist lobby have been playing this card every few years since the 1920s and, even if it were true, this would be another strong reason why cannabis possession and supply should be legal and regulated, so that quality and supply could be monitored and use by young children eliminated.
I'm now 49-years-old and have been taking cannabis for more than 30 years. If I can find a good, clean source, then I won't turn it down.
I started taking it as a teenager for pain relief. I had undergone a traumatic episode in my life and suffered extreme muscle damage.
My friends told me it was good medically, so I thought it might help me.
I'm not addicted though. I don't climb the walls if I don't get any.
I have a great interest in cannabis and have tried to carry out as much research as possible into the scientific facts surrounding it without being influenced by the pro or anti lobby.
I have had negative effects but only when I have taken doctored cannabis, which has been mixed with things like horse tranquiliser. That is why I try to only use the pure stuff.
When I saw this study, my first reaction was "oh god". If you have any mental illness and you use drugs and alcohol, then it is likely to have an effect, but to say it causes psychosis - that's wrong.
I don't drink but I do take cannabis, however, I would tell children not to dabble - in the same way they shouldn't with other substances.
Jim Wilson, Aberdeen
It was then I started hearing voices and became delusional”
I smoked cannabis a couple of times when I was 24-years-old. I used to hang around with some people who regularly took it.
I used to work with my father and my brother in the butchery business but after I started taking cannabis I started showing signs of psychosis.
I was diagnosed with schizophrenia and had to spend some time in hospital.
I'm now 55-years-old and those few drags I took when I was younger definitely changed my life and made it go rapidly downhill.
I directly attribute my illness to the cannabis.
After I started taking it, I asked my mum at the family business if I could have a holiday as I'd been working rather hard, it was then I started hearing voices and became delusional.
My mum went to the doctor who asked me if I wanted to go into hospital. Initially I declined but about a month later, I agreed.
I've now been on medication for most of my life and would advise people not to dabble in cannabis.
I am fine now, but I am dead against the thought of taking anything that's harmful to the body.
Carol Wood, Leicestershire
Each person is different, and the way psychoactive substances affect people also varies”
I have worked as a drug advisor in the educational field for more than 20 years and the rubbish spouted about cannabis needs to stop.
Cannabis, like all psychoactive substances, will act as a catalyst for any pre disposition to a psychiatric or psychotic episode.
As it is usually taken in conjunction with other drugs especially alcohol, it cannot be easily concluded that cannabis alone is the culprit.
The fact that it remains illegal is probably a more relevant indicator as to why it is singled out.
People with a dual diagnosis - who have mental illnesses and take cannabis - how can you distinguish which one they got first?
In my own personal experiences, I know about four or five people who had "cannabis-related episodes" but they were also drinking at the time - so it was difficult to say what caused or contributed to it.
Each person is different, and the way psychoactive substances affect people also varies.
The other thing is that cannabis can sometimes help mental and physical problems. It can benefit certain types of auto-immune diseases.
I'm not pro or anti, but think these studies need to be considered in context.
More of your comments
I smoked cannabis for approximately 25 years and towards the end I felt like I was hanging onto sanity by my fingernails. Some of the worse symptoms included voices in the night, a constant dread of death, suicidal thoughts and intense mood swings. I never thought I would kick the habit until one day I was attacked by someone out side a supermarket due to my psychotic ramblings. This person probably saved my life or a least my sanity. Dominic, Luton, UK
I have been a user of of cannabis for the past 17 years and it has never stopped me from building a good professional career with qualifications and a senior post within a large multi national organisation. I think people forget that these studies can be easily directed at similar "drugs" like alcohol and cigarettes which although are publicised as being bad for your health are completely legal. It's easy to turn around and blame someone's personal failures in life on the fact they smoke cannabis, but in reality the person probably already suffers from some form of psychosis or is plain lazy to begin with. We should stop using this as an excuse and do the right thing which is to decriminalize cannabis, this would make it much safer for the millions of people that use it recreationally. Beavis, Birmingham, UK
I spent many years playing in bands in an environment where cannabis use is pretty much the norm. All it ever did for me was send me to sleep. My observation, for what it's worth: if you're not paranoid when you start smoking dope, you sure will be after you've been at it for a couple of years. David Ballantyne, Raleigh, US
I spent my student years smoking pot and thinking it was not only harmless but it made me more creative (if anything it made me more lazy). But then I gave up as I realised you can't lead a successful life and smoke cannabis. But for years I believed that it was non-addictive and should be legalised. Now I work for a rehab clinic and have been doing some research into drugs. I still believe it's not addictive but I was told by people working in rehab that about 10% of dope smokers end up with psychosis, and one expert I spoke to in London said that "cannabis is the drug that creates the most problems for psychiatrists". Rupert Wolfe Murray, Bucharest, Romania
I blame my son's suicide at the age 19 on cannabis use, he used it from the age of 14. I believe that cannabis use affected him badly, causing erratic behaviour and subsequent mental illness. Janine Gray, Caloundra, Australia