Rare Mutations and Schizophrenia
Geneticists have had only modest success in identifying specific genes responsible for schizophrenia, and the few they have identified account for a very small percentage of cases. Now researchers at the University of Washington have found evidence that duplications or deletions of short stretches of DNA—known as copy number variations or CNVs—play an important role. CNVs were found three times more often in schizophrenics than in controls and four times as often when the disease was diagnosed before the age of 13. Not surprisingly, the CNVs tended to cluster around genes important for brain development. Science, Vol 320, 539-543. Just four months later two other studies have confirmed these results. In addition, thanks to including 20-30 times more patients in the two studies, the researchers were able to identify specific locations of deletions critical to schizophrenia—on chromosome 1 and chromosome 15, as well as a previously-identified locus on 22. One of the variants tripled the risk while the other two increased the risk 10-fold. Nature, Vol 455, 232-236, and Nature, Vol 455, 237-241.
The Infection Hypothesis of Mental Illness Revisited
This is a very nice summary of current thinking on the role of bacterial and viral infection in causing mental illness. The article's particular contribution is its focus on an immune reaction to the infection as the actual cause. As a popular article, it does not include references to its sources, but it does identify the researchers, which can be useful in searching for research articles. Scientific American Mind, April/May, 2008, 40-47.
Smoking and Schizophrenia
Seventy to eighty percent of schizophrenics smoke, and pages 438-439 list several functions in the schizophrenic brain that are improved by nicotine. Now add one more. Researchers at the University of Illinois injected mice with amounts of nicotine equivalent to constant, heavy smoking. This reduced a protein called DNA methyltransferase 1 (DNMT1), which in turn led to an increase in the protein that produces the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). DNMT1 levels are excessive in the brains of schizophrenics; apprently one of the many reasons they smoke is to increase GABA and damp down brain activity. Proceedings of the National Academy of Sciences, 105, 16356-16361.
