July 30, 2007

50 Top Experts Confirm Mental Health Risk of Marijuana / Cannabis

A new study published in the medical journal The Lancet last week says that people who use marijuana are 40% more likely to develop some form of psychosis than are those who just say no, and the risk soars for the heaviest users, with a risk increase of between 50% and 200% for the most frequent users of marijuana / cannabis.

The findings by the team at Bristol and Cardiff Universities in the UK, led by Dr Stanley Zammit, said that some 14 per cent of psychotic episodes among young people could be prevented if they avoided the drug.

There is now enough evidence to warn young people that using cannabis could increase their risk of developing a psychotic illness later in life, the Cardiff University study has found.

Cannabis, or marijuana, is the most commonly used illegal substance in most countries, including the UK and USA. In studies over the last decade up to 20 per cent of young people (aged 14-21) in different parts of the world have used cannabis regularly (at least once per week) or used heavily (on more than 100 occasions in total).

Dr Stanley Zammit in the School of Medicine’s Department of Psychological Medicine and colleagues at the Universities of Bristol, Cambridge and Imperial College, London analyzed 35 studies dated up to the end of 2006. The researchers assessed the strength of evidence for a causal relationship between cannabis use and the occurrence of psychotic or other mental health disorders.

The study, funded by the Department of Health, found that individuals who had used cannabis were 41 per cent more likely than those who had never used the drug to have any psychosis (presence of delusions or hallucinations). The risk increased relative to dose, with the most frequent cannabis users more than twice as likely to have a psychotic outcome. Depression, suicidal thoughts, and anxiety outcomes were examined separately, and findings for these outcomes were less consistent, with fewer attempts made to address non-causal explanations than for psychosis.

Dr Zammit, School of Medicine said: “The studies we looked at showed a consistent association between cannabis use and psychotic symptoms, including disabling psychotic disorders such as schizophrenia.”

“Despite the inevitable uncertainty, policymakers need to provide the public with advice about this widely used drug. We believe that there is now enough evidence to inform people that using cannabis could increase their risk of developing a psychotic illness later in life.”

If having ever used cannabis increases the risk of a psychotic outcome by 41 per cent as indicated by the results of the study, about 14 per cent of psychotic outcomes in young adults in the UK would not occur if cannabis were not consumed.

Additionally, a recent poll of more than 50 of the world's leading authorities on drugs and mental health confirms that most believe cannabis, and particularly its stronger variant, called "skunk" in the UK, pose significant health risks and increase users' susceptibility to psychosis and schizophrenia.

Read more: The great cannabis debate: 50 top experts confirm mental health risk

Psychosis From Pot?
(Science Magazine)

Read The Lancet Editorial - The study, along with the editorial and a commentary, are here. (PDF file for download)

Good Summary of Research: Cannabis / Marijuana (and other street drugs) Have Been Linked to Significant Increases Risk for Schizophrenia


I'm hoping someone in the psychiatric research field could confirm to me that the people who came down with schizophrenia from supposedly very heavy marijuana use were people where in their blood line, there was no elevated family disposition to schizophrenia, nor were these people a bit on the weird side before they smoked marijuana. Otherwise these studies linking cannabis use and schizophrenia are only proving there is a disproportionate number of schizophrenics who were heavy cannibis users before they became sick. I do not advocate smoking marijuana, I believe it is harmful to your health, and the psychological effects on you negatively impacts those you interact with daily.

Toronto Canada

Posted by: Tracy Malloy at August 1, 2007 07:51 PM

I agree. My son has been diagnosed with addiction with psychosis and schrizophenia. I have been to hell for the last two months and still struggling.

MY SON IS MY LIFE AND I LOVE HIM VERY MUCH. This is destroying and tearing us apart. There is no place to put a 19 year old with this diagnosis for a long term stay like 3 - 6 months. Of course this is voluntarily and my son believes there is nothing wrong with him and will not admit this to get the treatment he needs to get better. SO WHAT HAPPENS?

Posted by: Joanne WisemaN at August 4, 2007 10:16 PM

Back again continuation from my previous comment. I do believe that cannabis leads to mental illness. My son was using this a lot along with certain street drugs and hard liquor (straight from the bottle) and now he is not my son.

I can go on about the list of my son's behavior and the struggles but I would be here all night. He is determined to do one thing and I cannot allow that to happen while he is living with me. It is killing me to see him in such pain and yet I cannot legally put him somewhere to get better because he is 19 years old.

Posted by: Joanne Wiseman at August 4, 2007 10:35 PM

my wife was suffering from schizophrenia.still taking medicines.I got this site very informative so thanks.in India even learned people think it a evil soul & it is lack of awareness & information about these disease. Anyway thanks all of you for this all. and my Dr. K K singh,patna India.

Posted by: manish kumar at September 18, 2007 01:10 AM

my husband was hospitalized with schizophrenia while in the army and given a antipsychotics drug he was kept hespitalized for 6 months and was discharged with no medication or follow-up information he was discharged horonable, with a clean bill of health this was done in 1972 since then he has been fired from more jobs than i can count had run in with the law truble with drugs and alcohol,he moved by home with his mother and father in 1982 where he lived until we married in 2000 i didn't know his past before we married for he was a truck drive and when he was home he seamed normal we have been marrie 7 year in that time he has lost 3 jobs the last one was because of a dui he has been out of work for over a year now and he dosen't drink or do drugs he dosn't leave the house he is withdrawn and when he does talk he tells me about his dreams and they are many i found out about his schizophrenia when i insisted that he apply for ptsd from the army and this was in his reply letter. he won't go to the doctor for treatment i am lost and have no idea of what to do i have been reading everything i can about schizophrenia. Help

Posted by: annette at September 21, 2007 10:36 PM

THC is a drug that changes brain function, and is stored in the fatty tissues of the body , the brain being one source. THC in the developing brain of adolescents can be devastating causing withdrawal from family, school, depression, loss of motivation and memory. As a teacher of health and science at the middle school level I am angered by the "adults" who proclaim the benign effects from this drug. Those who say marijuana is "natural" well so is arsenic. Drug use for the teen can have life changing consequences. Please do not tout marijuanas benefits?, you must have never been a mentor or parent to a teenager.

Posted by: Janette Goeglein at October 24, 2007 06:10 PM

I personally feel that although it does have its side effects, being memory loss and what not, marijuana is a plant that is very beneficial for me (aand others)
I have Temp Lobe Epilepsy and one of my meds I'm on is to calm me, this med gave me horrific side effects. From intense nausea, to feeling like a total zombie, a burning stomach, partial swelling on my throat making it not fun to breathe, it took away my passion for everything and I just did not care about anything, and I didnt care that I didnt care.
After experimenting, I found that cannabis gave me the positive effects of what my med gave my without the awful ones. It just frustrates me that what works a lot better for me health wise is illegal and what is damaging my body is so many ways (more than Cannabis ever could) and making me feel the way I do... is perfectly legal.

And then in top of THAT, alcohol is legal.. It makes absolutely no sense that alcohol is legal and Cannabis is not. Everyone KNOWS how many accidents, deaths and abuse has its roots in alcohol.

Posted by: Cat at November 7, 2007 09:42 AM

Anybody noticed the update:


I wonder why it hasn't received the media attention the "positive link" stories got? Hmmm?

Looks like I might have to revise the intro to my chapter...

Posted by: Harry Stottle at December 8, 2007 05:49 PM

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