Genes R US — Schizophrenia: Is it the ‘unluck’ of the Irish?
Posted: Wednesday, March 21, 2012 5:00 pm
Aine was still a toddler when her mother, Caitlin, was institutionalized for “premature dementia.” Caitlin remained institutionalized until her death almost half a century later. Schizophrenia was not a word commonly used at that time. Aine’s son, Sean, was diagnosed with schizophrenia in his late teens. His recreational use of marijuana likely contributed to its onset.
On St. Patrick’s Day, 23 years ago as of last Sunday, I first spoke to my Irish mother, Aine, and learned of Caitlin’s and Sean’s unfortunate fates. Caitlin lived in a time with no good options for therapy; Sean had options but no compliance.
It is estimated that 1 percent of the people in the world will develop schizophrenia in their lifetime. The risk of developing schizophrenia in identical twins is 48 percent, in fraternal twins 17 percent, in non-twin siblings 9 percent and in half-siblings 6 percent. A grandparent adds in another 5 percent risk. However, most cases of schizophrenia are sporadic with no first degree relative having the disease.
The statistics above disclose a significant genetic liability (or predisposition) to schizophrenia; but there is an environmental component that appears to be every bit as large. Environment includes everything from gestational conditions, stress in childhood, drug use, viruses, nutrition and who know what all.
My risk increased to 11 times greater than the average person having Caitlin and Sean as relatives.
Schizophrenia is not a split personality disorder — a common misconception. Schizophrenia is characterized by hallucinations, particularly hearing voices, strange delusions and bizarre thinking and acting out. It is uncommon to develop symptoms of schizophrenia under the age of 10 or past the age of 40, but it can happen.
In schizophrenia certain parts of the brain appear to be too active due to an abundance of neurotransmitters, particularly dopamine and possibly serotonin. Medications aim to diminish the effect of these excessive neurotransmitters, and for the most part are profoundly effective if the patient complies by taking his medications.
Patients have trouble complying with their prescription regime due to the unpleasant side effects and the illness itself. Seventy-five-90 percent of adults with schizophrenia self-medicate by smoking tobacco to reduce some of the symptoms of the disease.
The World Health Organization puts schizophrenia in the top 10 of illness in suffering in the world. Certain parts of the world have higher rates of up to 4 percent, including parts of Ireland, some Scandinavian countries, Bosnia and Herzegovina and Croatia.
There are two theories about the genetics of schizophrenia. The “polygenic” proponents believe that hundreds of common variations in DNA increase one’s risk by just a tiny amount each. But those small risk factors can add up, and with the right environmental conditions, one develops the disease.
The “rare causal mutation” proponents believe that those hundreds of tiny genetic risk factors may simply provide a background for the real culprit, a rare genetic mutation to spring into play with the right environmental triggers. And that rare variant could change for the different families.
The research approach is different for the two theories.
“Polygenetic” proponents want larger studies of patients and controls with common SNPs; whereas, the “rare causal mutation” proponents emphasize deep sequencing of afflicted families.
The personal genetics company 23andme reports on only two SNPs (single-point DNA variations between people) associated schizophrenia. One SNP confers a tiny higher risk and the other confers a tiny protective factor. I have neither version, nor does Aine or my son, who have both been tested.
A Nature Genetics study published just this month reported that 23 percent of the genetic liability of schizophrenia is due to common SNPs. Scientists found 2,725 genes, expressed in the central nervous system, that explain a disproportionate amount of the variation.
Simple counting reveals that twice as many people develop schizophrenia as Alzheimer’s disease and that six times as many people develop schizophrenia as insulin-dependent diabetes in their lifetime.
It has been estimated that one-third of all the homeless have either untreated schizophrenia or bipolar disease. (By the way, bipolar disease and schizophrenia share many common genetic markers.)
Perhaps as our understanding of schizophrenia advances, the stigma of all mental diseases will be lifted. Then perhaps those suffering will be more open to seeking medical treatment. And perhaps those fortunate enough to escape its vicious claws will render more educated and compassionate support.
Editor’s note: Nancy Miller Latimer has worked in scientific research and development for 27 years. She blogs at NeuronalBeauty.BlogSpot.com. Published in The Messenger 3.21.12