Mental health charity Rethink has warned of possible links between cannabis and mental illness, and urged the government to launch an inquiry.
The drug was downgraded last year from Class B to Class C to save police time and allow them to target hard drugs.
The charity suggests reclassification has sent a "confusing message" to young people and that the number of drug smokers who developed mental problems has gone up by 60%.
Was downgrading cannabis the right move to tackle other types of drugs and drug-related crimes? Do you think cannabis should be reclassified? Send us your views.
This debate is now closed. Thank you for your comments.
The following comments reflect the balance of opinion we have received so far:
I personally have no objections to cannabis use when it is used responsibly - many people use it in my university and by and large they are well informed about the risks, with few problems as a result. People that want to will smoke it, legal or not, so it is the government's responsibility to ensure the public can make an informed decision. As for the drug's mental health effects, you may be surprised at how easy it is to come up with statistics that "prove" your point of view by a little mathematical trickery, an in-depth, large-scale, unbiased study is what is needed.
Adam, Cambridge, England
There is continuing hypocrisy with the cannabis debate. We have endless research and debates from people of both sides that want either to legalise it or make it a hanging offence for possession. When will a detailed and independent study into the effect of alcohol be carried out and will it be reclassified according to how dangerous it is? I had a personal friend that was an alcoholic and it ruined his family. Also A&E departments are overwhelmed at weekends with alcohol related problem. Cannabis for now has been graded a class C drug let's leave it at that. But if alcohol were to be reclassified it would have to be either a grade A or B drug, that would lead us back to prohibition, and we all know what happened when alcohol was last made illegal. Pure hypocrisy.
It should have been legalised years ago, so that it, and by consequence its strength, can be regulated. I'm not surprised that some very heavy users have had mental problems - if one went at alcohol in a similar fashion the result would doubtless be chronic alcoholism and liver damage. While remaining illegal it is simply being left in the hands of the racketeers, with all the inherent dangers of association with more dangerous drugs.
It seems strange that possible effects on health are being put forward as the argument against legalising cannabis, when tobacco is legal despite its harmful effects having been well-known for years. So reclassify it - however, as a lifelong non-smoker with no desire whatsoever to try cannabis, I would hope it would be prohibited in enclosed public places.
Lynne C, Chudleigh, Devon
The cynic in me says that it is probably socially more acceptable to smoke cannibis than to light a cigarette in a pub or restaurant. However, I find it scary that young teenagers (12 +) in my neighbour hood can easily get hold of cannabis and not think they are doing anything wrong/dangerous.
I don't see how 'a drug is dangerous' leads to 'it should be reclassified', they're two different issues. Many European countries (Portugal, Italy, Belgium) have less stringent cannabis laws than we do and lower levels of usage. There is no causal link between the law and how much people use the drug. Legalise it, tax it heavily and plough the taxation back into preventative health campaigns that have actually been proven to have an impact!
Gez Smith, Bristol, UK
Most cannabis ingested in this country is done so in conjunction with tobacco. Therefore it would seem pertinent that any credible study into a possible link with mental illness must surely take this into account.
Brendan MacLean, Birmingham, UK
If cannabis was to come out as a new drug today, it would be legal, like alcohol and tobacco. It was criminalised in a far more conservative age. If the government was to ban alcohol and tobacco it would be seen as nanny statism. The right is terribly incoherent on these issues. They either want bans and as many people in prison as possible or freedom of choice and no nanny statism. The anti-cannabis campaign aren't so much pro-mental health as anti-enjoyment.
Adam Johns, Cardiff, UK
We have had almost four years of anguish over our son's behaviour who is now 16. His behaviour changed over the course of about a month when he was almost 13. When we sought professional help we were told he had extreme "Oppositional Defiant Disorder". Three years on, after he actually asked to see a psychiatrist because he thought "his brain wasn't right", we now know he has been using cannabis two or three times a week for almost four years. The consultant told us there is no way of knowing how strong cannabis is now because it's genetically modified and can contain a varying % of psychoactive chemicals. Our son has provisionally been diagnosed with depression, anxiety and some paranoia. He has been prescribed anti-depressants and has been told to keep away from cannabis. We pray that his condition does not develop into schizophrenia. We've been told by teenagers we know that practically all teenage boys use it - it begins in year 8. Apparently it's "cool" for girls not to use it if they don't want to but not so for boys.
I'm 14, and in health lessons they tell us about drugs. That it's our decision and our life. They give us the facts and I think- why would anyone want to take drugs? This issue is complex, and I don't know enough about it to say. But I do know that it'll take a long time to find the best methods to cut down on cannabis use (not including for medical purposes). I think more teenagers will think it's OK to have cannabis if its Class c, but at the end of the day, everyone has got to make their own choices.
Whatever happened to freedom of choice? I personally don't smoke it but it has to be said that both alcohol and cigarettes also cause problems but the government doesn't mind reaping our taxes. Nothing will prevent people from doing it if they want to.
I am very confident that cannabis can trigger mental health problems. I smoked it for 7 years, when I was 14 until I was 21. The drug causes paranoia, and this is why I gave it up. At first I would only smoke it at week-ends, then I smoke every other day. But by the time I was 16 I couldn't go for a single day without the weed. I spent thousands of pounds on it, lost contact with my family, messed my education up, I was constantly stressed without it! I became very drowsy, and would often forget things. I believe this is something I still have not recovered from. In the end I was very depressed, almost scared to go out, permanently seeking out more, and more weed. Getting off cannabis was the best thing I've ever done.
Ex User, Liverpool
Having recently returned from Amsterdam I was impressed with the Coffee Shop culture. I would far rather my children be able to walk into a shop and buy cannabis than have to deal with the dealers who probably have a lot of other nastier things for sale.
Simon, Leeds UK
As someone who regularly sees the effects of cannabis use on patients there is no doubt of the serious long term effects on their mental health in a substantial number of cases. There are always people who will get away with using anything but that is not an argument that anyone should use to promote a dangerous practice. This stuff is dangerous and for many it is very dangerous - permanently affecting their mental health.
Dr R SW, UK
Marijuana is one of the most benign and therapeutic substances available, proven to help in such a wide variety of ailments. Many studies show that most cannabis smokers report a higher quality of life than non-smokers in a quality of life inventory. People who are predisposed to mental health problems where pot might be a trigger, will most likely find that same trigger in another aspect of life, pot is just the scapegoat.
Greg Witts, New York, USA
Like many other substances that some people abuse or are not suited to, cannabis is used by large numbers of people who find it fun and sometimes useful. It should be legalised, licensed and taxed. 'Declassification' is a cowardly half way house - production and supply is still in the hands of organised crime and there is nothing to stop minors getting hold of it. Quality is questionable because it is illegal and that is probably worsening some of the negative effects.
Katherine, London, UK
I was a very heavy cannabis smoker for about 3 years, waking up with a joint, and going to bed after one. I even worked in an Amsterdam coffees hop for a year. My experience is that cannabis can be harmful if smoked on a daily basis. Heavy smoking is a bad thing though and for me proved most detrimental, killing every shred of ambition that I had towards getting a better job, paying my bills and getting over my depression etc. In the end it got me into a lot of problems with the bank and the state and I was so depressed that every day I thought of ending it all. Now that I have been living away from Amsterdam in Barcelona I see what kind of danger cannabis poses to the smoker and hope that people think twice before lighting up. Once a week on a Saturday night it should not be a problem but if you smoke daily, seek help, you need it!
Jose F, Barcelona, Spain
Of course cannabis should be reclassified. It should be made legal. People take drugs because they like to. Making drugs illegal simply puts a vast, billion pound trade into the hands of organised crime, who then use this to corrupt and undermine law enforcement agencies (and sometimes governments) the world over. People who use drugs do not regard themselves as criminal any more than did people who drank alcohol during prohibition in the USA. They do not wish to buy drugs from criminals, but at present have no other choice. Legalise drugs, subject them to the same levels of control and taxation as alcoholic drinks, and most of the problems associated with them will go away.
Max S, Athens, Greece
Alcohol has caused more deaths than cannabis ever could. Alcohol will never be illegal because the people who decide what's legal and what's not probably enjoy a nice drink at the end of the day.
Seastron, Newark, Notts, UK
People have been smoking cannabis forever. There is no law, punishment or decree that is going to change the situation; people will do whatever they want to regardless of whoever tells them otherwise. That is life.
Mark Harper, Fife
Cannabis should not have been downgraded. I, as a former drugs squad officer knew as far back as 1974 that cannabis was a harmful drug and caused psychological addiction. Unfortunately New Labour thought it fit to down grade this drug to help their crime figures. Next thing they will say shop-lifting isn't an offence so they can concentrate on burglary or indecent assault isn't too bad so they can concentrate on rape. Hey, but never mind, we have a new problem now, binge drinking so let's open all ours. God help us.
Odd that the results of any survey seem to reflect the viewpoint of the organisation that sponsored it. What about the theory that people who have a predilection towards drugs probably already have a mental illness?
Peter Connolly, Derby, England
The government makes no effort whatsoever to minimise the risks associated with cannabis use. There should be specific campaigns to discourage mentally ill people from using the drug, or to stop people smoking joints made with tobacco. Instead, it's simply classified as illegal, and all we get is a puritanical "don't do it at all" message. It's about time we dropped our simple-minded approach to drug abuse, and accept that it is a complex problem that requires complex solutions.
Johnny W, Hull, England
My son has schizophrenia which is linked in some way to his use of cannabis. Cannabis should be legalised so that clear believable messages about its safe use can be given out. It's entirely up to adults whether they use it or not but they need to know the facts about its risks. Keeping it outside the law and uncontrolled does nothing to help people like my son.
Amy, London UK
People who tend to get mental illness from drug abuse tend to take other stronger drugs like LSD and magic Mushrooms in conjunction with smoking weed. The other drugs, without doubt cause mental illness, but smoking cannabis on its own has never proven to cause mental illness as this government report will show. And if it does not show a link between Cannabis and psychosis will the government end the prohibition on a harmless substance recognised for its recreational and medical uses in most of the countries of this world. Roughly one third of countries in the EU already have cannabis as a decriminalized substance, when will the government of this country follow suit?
Downgrading cannabis really wasn't much of a move at all - it hasn't helped and has created confusion. What I'm certain about is that reclassifying whilst carried out a study will be even less helpful: yet another case of act first think later. Why not carry out the studies and then take action? Personally I think it should be legalised, but keeping it class C whilst investigating it seems the best compromise at the moment.
Stephanie, Edinburgh, Scotland
Even in the Netherlands they are talking about banning cannabis with a high THC content (the active ingredient)so we should really be very careful before rushing down a path where others have gone before and experienced problems. As a nations we have problems with binge drinking, so we don't want to legalise any other drugs if we can't cope with the current ones. 'Sane' the mental health charity has referred to cannabis use as 'Russian Roulette' you might be fine or it might trigger schizophrenia or psychosis.
Craig Lewell, Manchester
It should be legalised, not reclassified.
Iain, Cambs, UK
I have smoked cannabis for years, and suffer severe anxiety and depression. I have been trying to stop for a year and when I manage to go most of the day without a spliff I feel so much better. I cannot go a whole day without a spliff and the more I smoke the worse I feel, yet I get so agitated if I don't smoke. I defiantly think there needs to be further investigation and should be reclassified until they have properly researched it.
It does give mental problems as my girlfriend who was a long term user suffers from them.
Steve, Plymouth, UK
I don't think the classification of cannabis is the issue. People will smoke it however it is classed. The problem with all drugs is that those who feel the urge to take them are those who have the genetic makeup to become addicted, and for this there is no answer.
Gwyn, Crewe, UK
Fair enough if there are links put a warning on the box. Just like you would any other product that can be potentially dangerous. Just because something has a danger factor does not make it illegal - otherwise we need to reclassify everything. Starting with cars, aspirin and step ladders! If something is used incorrectly it is dangerous but if you use it knowing the dangers then you are more likely to be careful and respectful.
I am reading people say cannabis is not addictive - how long have you smoked? And have you tried stopping? I have smoked 10 years, and can't go a day without smoking. I smoke about an eighth of weed a day, although it does vary down to a tens if I am trying not to smoke. More research into the long term effects of this drug needs to be done for the sake of my children and my nieces and nephews as I only smoked cannabis because I thought it wasn't addictive, I don't want my children making that same mistake, and if people are so sure its not a problem what's the harm in researching it.
I feel that any research done on the issue seems to be have either been conducted or funded by parties with vested interests. I'd like to see some actual clear independent research before I jump to any conclusion.
Your comments regarding cannabis are seriously flawed. Cannabis is a benign herb with many healing and therapeutic qualities and helps many sick people cope with pain associated with a variety of illnesses. The "cannabis" which is purchased on the street is only 2% of the real herb. The remainder is any old rubbish which is put in including human faeces.
This is generally known as "Soapbar" and it is this awful product which will be adversely affecting people. I have MS and have been using cannabis for 4 years now. My last relapse was four years ago. When I say using I use the term loosely because I consume it, I don't smoke it. It helps in a magnitude of ways.
Carol Appleyard, Glasgow
It should be legalised. Cigarette smoking causes all sorts of horrible cancers and has the potential to affect other people as well as the smoker, yet that is still legal. Confusing? I think so.
Rob, Stafford, UK
To Rob, Stafford, UK: I find it more confusing that given the problem of smoking in our society, your solution is to choose to make things worse.
BFA, Indy, IN, USA
I'm surprised that the government has not made cannabis legal by now, that way it could tax it!
Adrian Mugridge, Chester, UK
Junkies will ask for cannabis to be legalised. Those with more sense will want to keep it illegal. It's sad when someone has to use a mind-bending drug to improve their sorry lives.
Cannabis Sativa might be an old word for marijuana. Today's marijuana if not home-grown is most likely corrupted with chemicals to allow for a profit, while selling small quantities. Being 52-years of age and a high schooler in the 60s I'm no prude. Cocaine(crack) and Ecstasy have created some type of economic race between rival gangs. They are not well endowed with intelligence or scrutiny. They also lack basic human pride. Insulting women seems to top off a day's work. Too lower the penalties and search out harder criminals with drugs is wise. But to set some story about that cannabis is still a "hippie" drug is false.
MS Mocarski, Danbury, CT, USA
Yes. It was an idiotic move to downgrade it in the first place. I see the government has stated that the re-classification has been a great success, as it has saved 2000 hours of police time. Sorry? It's a success because it has saved time? Not because it has reduced cannabis use (it hasn't)? What kind of criteria is that? What kind of government - what kind of country measures success by 'police time'. Perhaps we'd better declare burglary legal, that should save a few hours! Maniacs, the lot of them.
A. Howlett, Cheshire, England
Why don't people value their own lives and adopt healthy lifestyles? It is so mind-boggling and totally disconcerting that people are prepared to play Russian roulette with their lives. If there is a link between cannabis and mental illness the onus lies with the victim for being so callous!
Pancha Chandra, Brussels, Belgium
Can't alcohol effect your mental state when taken regularly?...sorry that drug is okay because it's taxed, silly me...my mistake
Definitely. People are under the illusion that cannabis is somehow "healthier" than smoking because of its analgesic effects. Instead, it has the combined effects of alcohol and smoking; intoxicating you beyond the ability to drive and work safely, plus destroying your physical and mental health. People with MS only want to ease their pain, not cause trouble - unlike the public at large. Possession arrests have only dropped because no-one is actually being arrested; people haven't suddenly begun to behave themselves.
Philip Pike, Colchester
Does cannabis use contribute to mental health problems, or are the mentally unhealthy more likely to use cannabis? Either way, I'm willing to bet that the correlation between mental disorders and alcoholics is (in the very least) just as strong. But then again cannabis lacks alcohol's powerful lobby.
G Legge, Pontdolgoch
Downgrading cannabis to Class C was a move in the right direction, but it didn't go far enough. I don't understand why some people think that they have the right to declare someone else a criminal for using cannabis! Just how is that supposed to help?
Lawrence, Sheffield, Great Britain
Yes it can be dangerous to the vulnerable, but decriminalisation would still be the best option. There's less users per head in Holland, where the laws are more relaxed. Obviously there needs to be more awareness on mental health, but the media should stop all the propaganda, which is also dangerous.
C Johnson, Newcastle