Cannabis use raises risk of schizophrenia - study

Medical research carried out in the UK and Sweden by a team that included a Maltese psychiatrist has indicated that cannabis use increases the risk of a person suffering schizophrenia.

The Maltese psychiatrist, Stanley Zammit, formed part of a research team that included Peter Allebeck, Sven Andreasson, Ingvar Lundberg and Glyn Lewis. An abstract of their findings was published in the British Medical Journal.

Men who had smoked cannabis by the time they were 18 were more likely to develop schizophrenia over the following 27 years. The more cannabis people smoked in their teenage years the greater the risk.

Dr Zammit is a clinical research fellow with the British Medical Research Council (MRC).

In an interview while on a short visit to Malta, Dr Zammit said schizophrenia is an illness that affects about one per cent of the population. It is characterised by symptoms such as hallucinations, hearing voices and delusions where people have strange, abnormal or paranoid beliefs.

"I am looking at what sort of factors increase or decrease people's risk of developing this illness."

The MRC funds doctors for three to four years to do a research project and continue their training in a specialised area.

Dr Zammit explained that such research is done mainly using data from Sweden, which collates a vast amount of information as part of its conscription procedure.

"The reason we used conscripts is that they are healthy young men and the findings are fairly generalisable to young men. The main onset of schizophrenia tends to be in young adulthood in the mid-20s".

The conclusions one draws from research are really limited to the group under study but, nevertheless, most risk factors for diseases carry across or extrapolate across different age groups and genders as well.

He said that to collect enough people who are going to develop schizophrenia one needs a vast sample before they develop the illness and one has to follow them up for a length of time.

"With this cohort we had 50,000 people followed up for 30 years and we only ended up with 350 people who actually have schizophrenia.

"That isn't a huge number but if you want to study a rare illness in this way you have to start off with a huge sample. Because in Sweden, unlike the UK, you are able to link databases, you can link that information with whether people have been admitted to hospital for any particular diagnoses," Dr Zammit said.

Schizophrenia

As with most disorders, there is a genetic component to schizophrenia. In other words, if there is someone in your family who has schizophrenia, you have an increased risk of developing the disorder.

There are other factors that increase the risk. Crossing the threshold into the illness is probably an interplay between genetic factors and environmental factors.

There is no single cure for schizophrenia but there are treatments for its symptoms. If somebody has hallucinations hearing voices there are medications that can help to reduce the intensity or the frequency of those experiences.

The symptoms can be very distressing and patients are usually extremely scared of the people around them and often paranoid about the medical or the psychiatric profession who are trying to help them.

That makes it extremely difficult to treat people. Patients often lose motivation and become apathetic and that, in combination with the other symptoms, often means that people are unable to work properly and to develop normal social relationships.