April 29, 2006

Gene linked to schizophrenia also tied to intelligence

A new research paper authored by psychiatric researchers at The Zucker Hillside Hospital and Harvard Partners Center for Genetics and Genomics in Boston, examined the genetic blueprints of individuals with schizophrenia and compared them with healthy volunteers.

They discovered that the dysbindin-1 gene (DTNBP1), which more than 11 other research studies have previously demonstrated to be associated with a person's risk of developing schizophrenia, may also be linked to general cognitive ability. The study is being published in the May 15 issue of Human Molecular Genetics, available online.

"A robust body of evidence suggests that cognitive abilities, particularly intelligence, are significantly influenced by genetic factors. Existing data already suggests that dysbindin may influence cognition," said Katherine Burdick, PhD, the study’s primary author. "We looked at several DNA sequence variations within the dysbindin gene and found one of them to be significantly associated with lower general cognitive ability in carriers of the risk variant compared with non-carriers in two independent groups."

The study involved 213 unrelated Caucasian patients with schizophrenia or schizoaffective disorder and 126 unrelated healthy Caucasian volunteers. The researchers measured cognitive performance in all subjects. They then analyzed participants’ DNA samples. The researchers specifically examined six DNA sequence variations, also known as single nucleotide polymorphisms (SNPs), in the dysbindin gene and found that one specific pattern of SNPs, known as a haplotype, was associated with general cognitive ability: Cognition was significantly impaired in carriers of the risk variant in both the schizophrenia group and the healthy volunteers as compared with the non-carriers.

The study, published online in the journal Human Molecular Genetics, found that the variant form of dysbindin-1 that is associated with lower intelligence was present in 7% of the general population and 12% of the schizophrenic population. In addition to an increased risk of schizophrenia, individuals who posses this gene variation can also expect to perform 3% to 5% percent worse on standardized neuropsychological cognition tests, which rate a person's mental skills in reading comprehension, attention, verbal fluency and memory.

To learn more about schizophrenia genetics - click here.

This new study may also help explain previous research reports linking higher IQ with lower risk of developing schizophrenia. Additionally, with the increasing number of research studies that are validating a dozen or so key genes that are linked with significantly increased risk of develping schizophrenia - its quite possible that new genetic tests will soon be able to determine a person's genetic predisposition for developing schizophrenia (and therefore make easier to identify the people who should make special effort to avoid key environmental factors that have been linked to the development of schizophrenia).

The specific role of dysbindin in the central nervous system is unknown, but it is highly present in key brain regions linked to cognition, including learning, problem solving, judgment, memory and comprehension. Scientists speculate that dysbindin plays a role in communication between brain cells in these regions and helps promote their survival. An alteration in the genetic blueprint for dysbindin may ultimately interfere with cell communication and fail to protect brain cells from dying, with a resulting negative impact on cognition and intelligence.

The study was funded by grants from the National Institute of Mental Health; National Institute of Child Health and Human Development; NARSAD, The Mental Health Research Foundation (formerly known as National Alliance for Research on Schizophrenia and Depression); and Stanley Medical Research Institute.

Source: Genetic variation in DTNBP1 influences general cognitive ability. Hum Mol Genet. 2006 May 15;15(10):1563-68. Epub 2006 Jan 13.


Since when is schizophrenia associated with low intelligence?

According to your study - it only explained a small proportion of it - about 3 percent. This supports a model involving multiple genetic and environmental influences on intelligence

"new genetic tests will soon be able to determine a person's genetic predisposition for developing schizophrenia and therefore make easier to identify people who should make special effort to avoid key environmental factors in development of schizophrenia

Posted by: Fred at April 30, 2006 01:45 PM

"reports linking higher IQ with lower risk of developing schizophrenia."

Interesting. And since IQ tends to be somewhat fluid (as a former disability examiner, when it came to certain impairments, the approval criteria had to do with comparing current IQ with pre-morbid levels), this would seem to be an argument for maintaining the type of environment that is stimulus-rich. In fact, I just read something recently that stated that elderly individuals with well developed social networks were healthier in a cognitive sense. More input.

Posted by: Tim at May 3, 2006 11:17 AM

I have found through inquiry and observation that each of us has many facets to our intelligence-some facets bright some dark facets. As a schizophrenic I find it frustrating, when I polish a dark facet it doesn't grow brighter. But as a humanist I understand we all have limitations and our greatest happiness comes from making the most of our inate talents. Reading another article hear I am reminded how much my cognition limits me socially, yet the good nature buddhism has endowed me keeps me a few loving and devoted relations. More tests beyond employment aptitude are needed to guide us in fulfilling life-and the influence of some truly tansforming practices facilitate sharing our lives,

Posted by: Sean at May 19, 2006 10:31 AM

How is it that a sz's brain is more active, yet it is less intelligent? How is it that, "dysbindin plays a role in communication" between brain cells, to constantly keep them active- and mainipulate the "real" to the odd?
How is it that dysbindin the key ingredient for keeping all thoughts active- is making sz's less intelligent?
Why is sz on the rise?
What if it isn't a disorder, it is just a mutation that sz's can't control yet?
How many dimensions are there that physics has proved- what if they (my mom has it not me. . .yet)are seeing things and manipulating things that are present in different dimensions?
Wouldn't your brain melt down too?

By The Way, when my mom is under treatment- numbed zombie and all- i wouldn't expect her to preform well on an IQ test.

Posted by: cb at June 5, 2006 11:23 AM

It would be so very wonderful if the true cause is found and a medication found that helps without lots of side effects. My brother suffers tremendously from the condemning "voices" of schizophrenia. Clozaril helps some but they are never completely gone. It seems to me its like the negetive self talk we all experience on steroids! There must be a physiological cause that hasn't been discovered yet. He is so heroic, fighting his fears and anxieties daily.
and perservering!!! Its unfortunate the illness is so misunderstood and threatening to those who don't understand. These suffering ones deserve a heroic award for bravery for facing their inner dangers, without giving up!

Posted by: Mary at October 9, 2006 11:24 AM

This article almost seems as if it trying to persuade it's reader to believe that those who have schizophrenia are stupid and have lower IQs than a normal person. As a person who has schizophrenia, I find this to be kind of offensive. It mentions only three to five percent which is such a small number. I was an honor student and a gifted student as a child and scored well on the SAT. I think this study that was done was useless and only makes it seem as if schizos are not intelligent. Honestly, I couldn't score well on an IQ test while off medication but when I am normal and on treatment I am the same old person I've always been. Stop treating schizos as if they are retarded.

Posted by: judy at January 22, 2007 09:53 PM

i have sz and since treatment i know my cognitive abilitites have greatly diminished but i cannot attribute that to sz. Rather medications seem to be the reason.
p.s. if you think people with sz are less intelligent go watch a beautiful mind.

Posted by: skoe at April 16, 2007 06:32 AM

I wonder how could this happen bc i understand that as IQ increses the risk also increases

Posted by: ashenafi at September 27, 2007 11:48 PM

i agree that lowered intelligence seems to be due to medication. I suppose the psychiatrists will just see this as a sort of denial or something, but it's really true. I was a straight A student for 2 years actively psychotic (before I was diagnosed) and now since I've been on meds I can't even take a full course load cuz it takes me so long to read. I think the doctors say that as your schiz develops other functions diminish. but i think that's wrong. it's the meds. i know my body and mind and i can tell.

i took an i.q. test while in psychosis and got a 129, not as good as i'd hoped, but not to bad either (and i totally bombed one section i thought i'd do good on, so i think i messed up somehow). anyway i should take one now while medicated, then go off my meds for a certain amount of time and take it again... i wonder if there are any studies doing this now that i can get paid for doing that... lol...

Posted by: cmcsherry at October 22, 2007 04:26 PM

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