Study finds genetic links between schizophrenia and cannabis use

[Buster's Uncle]

Study finds genetic links between schizophrenia and cannabis use
Reuters
By Kate Kelland  June 24, 2014 4:04 AM



LONDON (Reuters) - Genes that increase the risk of a person developing schizophrenia may also increase the chance they will use cannabis, researchers said on Tuesday after studying more than 1,000 users of the drug.

The results chime with previous studies linking schizophrenia and cannabis, but suggest the association may be due to common genes and might not be a causal relationship where cannabis use leads to increased schizophrenia risk.

Cannabis is the most widely used illicit drug in the world, and its use is higher among people with schizophrenia than in the general population.

"We know that cannabis increases the risk of schizophrenia. Our study certainly does not rule this out, but it suggests that there is likely to be an association in the other direction as well – that a pre-disposition to schizophrenia also increases your likelihood of cannabis use," said Robert Power, who led the study at the Institute of Psychiatry at King's College London.

Schizophrenia is a common and severe psychiatric disorder that affects around one in 100 people. People who use cannabis are about twice as likely as those who do not to develop it.

The disorder typically begins in late adolescence or early adulthood and its most common symptoms are disruptions in thinking, language and perception. It often includes psychotic experiences, such as hearing voices or delusions.

While the exact cause is unknown, research to date suggests a combination of physical, genetic, psychological and environmental factors can make people more likely to develop it.

Previous studies have found a number of genetic risk variants associated with schizophrenia, each of which slightly increases a person's risk of developing the condition.

Cannabis use has frequently been associated with it, but there is much debate about whether this is because of a direct cause, or whether there may be shared genes which predispose people to both cannabis use and schizophrenia.

A study published in March 2011 found that people who use cannabis in their youth dramatically increase their risk of psychotic symptoms, and that continued use of the drug can raise the risk of developing a psychotic disorder in later life.

And earlier research found that young people who smoke cannabis for six years or more are twice as likely to have psychotic episodes, hallucinations or delusions.

This latest study, published in the journal Molecular Psychiatry on Tuesday, included 2,082 healthy people of whom 1,011 had used cannabis. Each participant's genetic risk profile - the number of genes related to schizophrenia each of them carried - was measured.

The researchers found that people genetically predisposed to schizophrenia were more likely to use cannabis, and to use it in greater amounts than those who had no schizophrenia risk genes.

Power said the result "highlights the complex interactions between genes and environments" when it comes to cannabis as a risk factor for schizophrenia.

"Certain environmental risks, such as cannabis use, may be more likely given an individual's innate behavior and personality, itself influenced by their genetic make-up," he said, adding that this finding was important to consider when calculating the economic and health impact of cannabis.

(Editing by Alison Williams)


http://news.yahoo.com/study-finds-genetic-links-between-schizophrenia-cannabis-080450400.html

[Buster's Uncle]

Cannabis Habit and Schizophrenia May Have Genetic Link
LiveScience.com
By Bahar Gholipour, Staff Writer  June 24, 2014 11:29 AM



People with schizophrenia and some who use cannabis may have certain genes in common, according to new research.

The findings may partly explain the following, long-established link between cannabis use and psychotic disorders: The rate of people who smoke pot is higher among those who are diagnosed with schizophrenia than it is in the general population. In addition, studies have shown that using cannabis can lead to psychotic episodes or worsen a person's existing symptoms, which suggests that the substance could trigger the psychotic disorder.

But the new results suggest that part of the association between the two might actually be due to both of them being linked with the same genes, said Robert Power, a researcher at the Institute of Psychiatry at King's College London.

"To some extent, those genes that we have identified as being 'schizophrenia-inducing' are also genes that can contribute to cannabis use," Power said.

Power and his colleagues looked at the pot-smoking habits of 2,082 healthy people as well as their genetic profiles, focusing on the genes that have been identified as related to schizophrenia.

The results showed that people who had genes linked with schizophrenia were also more likely to use cannabis, and use it more frequently, compared with people who didn't have the schizophrenia-risk genes, according to the study, published today (June 24) in the journal Molecular Psychiatry.

Schizophrenia is a psychotic disorder characterized by hallucinations, delusional beliefs and jumbled thoughts. The disorder is highly heritable — although it affects about 1 percent of the population, the risk jumps to about 10 percent for children with schizophrenic parents, and to 50 percent for twins with one twin having the disorder.

In the new study, the researcher also looked at about 1,000 twins, and found a stepwise relationship between genetic risk for schizophrenia and the likelihood of using cannabis. Those twin pairs who both reported the use of cannabis had the greatest burden of schizophrenia-risk genes; twin pairs with only one user had an intermediate level of schizophrenia risk and the lowest burden was found in pairs where neither twin reported using marijuana.

The results suggest that the potential role of cannabis in causing schizophrenia, which has in?uenced discussion over the legislation of the drug, may be slightly overestimated, the researchers said.

However, the findings are probably only part of a more complicated picture, Power said.

"I wouldn't say that there's no risk of cannabis causing schizophrenia, but that it's probably more complex a relationship that we are currently thinking," Power told Live Science.

It is possible that in fact both scenarios are true: that cannabis may cause schizophrenia, but also that people with schizophrenia are more likely to use cannabis for various reasons. For example, it may be because they are more likely to have a personality geared toward experimenting with drugs, Power said.

It's also possible that patients with mental illnesses may try cannabis to self-medicate. Studies have found that the drug can help alleviate some symptoms of schizophrenia, although those symptoms only become worse later.


http://news.yahoo.com/cannabis-habit-schizophrenia-may-genetic-152906370.html