Research by top scientists from Bristol, Cambridge and London Universities has revealed that there is little, if any link between young people smoking cannabis and developing schizophrenia.
‘Diagnostic categories like schizophrenia are simply concepts’
Findings, published in this month’s edition of the journal ‘Addiction ,’ show that thousands of people would need to stop using cannabis in order to prevent a single case of schizophrenia.
A disproportionately high number of people from African Caribbean communities who are given a diagnosis of schizophrenia when they come in contact with mental health services. This is despite black people having a similar prevalence to mental illness as any other ethnic group. Equality groups point out that the diagnosis of schizophrenia not objective in the same way that other psysical health conditions are detected.
Prof Suman Fernando is an honorary senior lecturer at the University of Kent and visiting professor at London Metropolitan University. Last year he turned down the offer of an OBE for his services to ethnic minorities using mental health services. Commenting on practitioners use of the diagnosis of schizophrenia in the British Medical Journal he said: ‘although sometimes useful for practical purposes even in a multicultural society, diagnostic categories are simply concepts, justified only by whether they provide a useful framework for organising and explaining the complexity of clinical experience.’
Scientist findings on cannabis and mental health clash with government line
These new research published last week, flies in the face of attempts by the government to reinforce the perception of the harm the drug could have on users mental health.
One of the authors of the report Dr Matthew Hickman, from the University of Cambridge and the London School of Hygiene and Tropical Medicine said that preventing the use of the drug was still important, in terms of reducing tobacco and drug use, and improving the performance of pupils at school. However he is clear reiterated that the link between cannabis and schizophrenia is very uncertain.
This new research follows last year’s decision by the UK government to reclassify the drug from class C to class B, partly out of concerns that cannabis, especially the more potent varieties, may increase the risk of schizophrenia in young people.
But the evidence for the relationship between cannabis and schizophrenia or psychosis remains controversial.
Mental health Tzar, Professor Louis Appleby, told the Home Office’s Advisory Council on the Misuse of Drugs in February 2008 that ‘the evidence is pointing towards cannabis as a cause of severe mental illness.
Warnings of link between cannabis and mental illness published online
The government have also published warnings of the link between using cannabis and developing mental illness later on in life on Frank, the publicly funded website set up inform young people about the dangers of illegal use.
The Bristol scientists, with colleagues from the University of Cambridge and the London School of Hygiene and Tropical Medicine, took the latest information on numbers of cannabis users, the risk of developing schizophrenia, and the risk that cannabis use causes schizophrenia to estimate how many cannabis users may need to be stopped to prevent one case of schizophrenia.
The study found it would be necessary to stop 2,800 heavy cannabis users in young men and over 5,000 heavy cannabis users in young women to prevent a single case of schizophrenia. Among light cannabis users, those numbers rise to over 10,000 young men and nearly 30,000 young women to prevent one case of schizophrenia.
Home secretary, Alan Johnson warns against campaigning against government policy
Their research also showed that interventions to prevent cannabis use typically do not succeed for every person who is treated.
Depending on how effective an intervention is at preventing cannabis use, it would be necessary to treat even higher numbers of users to achieve the thousands of successful results necessary to prevent a very few cases of schizophrenia.
This research comes fast on the heels of the highly publicised resignation of the Bristol University’s Professor David Nutt.
He was forced to step down from his post of chief drugs adviser to the government for making public his views that alcohol and tobacco were more dangerous than cannabis.
Home secretary, Alan Johnson accused the former drugs advisor of ‘campaigning against government policy. ‘However finding from this latest research backs the claims of Professor Nutt who is also head of Bristol University’s pharmacology unit has made.
‘Our evidence suggests that focusing on schizophrenia may have been misguided. Our research cannot resolve the question whether cannabis causes schizophrenia, but does show that many people need to give up cannabis in order to have an impact on the number of people with schizophrenia. The likely impact of re-classifying cannabis in the UK on schizophrenia or psychosis incidence is very uncertain,’ Dr Hickman said.
By Zephaniah Samuels