Schizophrenia Research Forum - A Catalyst for Creative Thinking
Home Profile Membership/Get Newsletter Log In Contact Us
 For Patients & Families
What's New
Recent Updates
SRF Papers
Current Papers
Search All Papers
Search Comments
News
Research News
Conference News
Plain English
Forums
Current Hypotheses
Idea Lab
Online Discussions
Virtual Conferences
Interviews
Resources
What We Know
SchizophreniaGene
Animal Models
Drugs in Trials
Research Tools
Grants
Jobs
Conferences
Journals
Community Calendar
General Information
Community
Member Directory
Researcher Profiles
Institutes and Labs
About the Site
Mission
History
SRF Team
Advisory Board
Support Us
How to Cite
Fan (E)Mail
The Schizophrenia Research Forum web site is sponsored by the Brain and Behavior Research Foundation and was created with funding from the U.S. National Institute of Mental Health.
Research News
back to News Search Plain English
Genetic Risk for Schizophrenia, Cannabis Use Overlap

June 30, 2014. Genetic variants that increase risk for schizophrenia also increase the chance that a person will use cannabis, according to a study published online June 23 in Molecular Psychiatry. The study, led by Robert Power of the Institute of Psychiatry at King’s College London, UK, examines the well-established association between schizophrenia and cannabis in 2,082 healthy people. The researchers found that those with a greater burden of schizophrenia risk variants were more likely to use cannabis, and more frequently, than those with a lesser burden.

The findings point to difficulties in teasing apart genetic from environmental influences on risk for a complex disorder. What may seem like a straightforward environmental factor may well have a genetic component, which could drive a person toward certain environments or exposures in the first place.

People with schizophrenia use cannabis more than the general population, and prospective studies find that cannabis use increases risk for psychosis (see SRF related news report). This suggests that cannabis use is one of several causal factors leading to the disorder. But others have proposed that the association between schizophrenia and cannabis stems from self-medication, or from the fact that people who are psychotic are just more inclined to partake in an illicit drug.

The new study provides yet another perspective by finding that genetic predisposition for schizophrenia can also account for some amount of cannabis use. Though the study does not rule out a role for cannabis in directly increasing risk for psychosis, it provides another example of how different outcomes (schizophrenia, cannabis use) can share some of the same genetic roots.

Of burdens and buds
First author Power and colleagues began by tallying, for each person, the burden of common risk variants for schizophrenia based on the single nucleotide polymorphisms (SNPs) identified by the Psychiatric Genomics Consortium’s latest genomewide association study (see SRF related news report). This resulted in a polygene score for each person, which reflects the combined effects of many genes toward risk for schizophrenia.

Those with the highest polygene scores were more likely to have used cannabis, whereas those with the lowest scores were not more likely to have done so. This association was strongest for polygene scores based on SNPs that had attained p values of 0.01 or lower in the previous GWAS. At this level, however, the polygene score explained a fraction (0.47 percent) of the variance in cannabis use. A significant positive correlation also emerged for the amount of cannabis use, but again accounting for a small portion of variance (0.85 percent).

The relationship between genetic risk for schizophrenia and cannabis use also held true in a separate group of 990 twin pairs. Pairs in which both twins reported using cannabis had the highest polygene scores; those in which only one twin used cannabis had middling scores; and those in which neither twin reported cannabis use had the lowest scores.

The authors note that the SNPs used to calculate the polygenic scores may not purely reflect schizophrenia risk, since it is possible that, in the GWAS samples, more cases than controls used cannabis. This means that some of the schizophrenia risk alleles identified to date may actually tag a person’s predilection for cannabis. Still, the findings suggest that the association between cannabis use and schizophrenia is a two-way street, and that both directions may be at work in schizophrenia.—Michele Solis.

Reference:
Power RA, Verweij KJ, Zuhair M, Montgomery GW, Henders AK, Heath AC, Madden PA, Medland SE, Wray NR, Martin NG. Genetic predisposition to schizophrenia associated with increased use of cannabis. Mol Psychiatry . 2014 Jun 24. Abstract

 
Submit a Comment on this News Article
Make a comment on this news article. 

If you already are a member, please login.
Not sure if you are a member? Search our member database.

*First Name  
*Last Name  
Affiliation  
Country or Territory  
*Login Email Address  
*Confirm Email Address  
*Password  
*Confirm Password  
Remember my Login and Password?  
Get SRF newsletter with recent commentary?  
 
Enter the code as it is shown below:
This code helps prevent automated registrations.

I recommend the Primary Papers

Please note: A member needs to be both registered and logged in to submit a comment.

Comment:

(If coauthors exist for this comment, please enter their names and email addresses at the end of the comment.)

References:


SRF News
SRF Comments
Text Size
Reset Text Size
Email this pageEmail this page

Share/Bookmark
Copyright © 2005- 2014 Schizophrenia Research Forum Privacy Policy Disclaimer Disclosure Copyright