New theory suggests genetic origins of mental illness
Published Sunday, November 23, 2008 7:52AM EST
Two scientists, one a Canadian, have developed a revolutionary theory for the basis of some mental illness. They argue that autism and schizophrenia are opposite disorders when viewed through the lens of the brain's development.
Prof. Bernard Crespi, an evolutionary biologist at B.C.'s Simon Fraser University, and Christopher Badcock of the London School of Economics, believe that the two disorders evolve depending on whether certain genes in the mother or father are imprinted, or silenced, during gestation.
Imprinting is particularly common in genes that are expressed in the brain, Crespi said, and is caused by a biochemical change in the germ line, the sequence of cells that contain genetic material that will be passed on to the child.
- If the mother's genes, which are growth-promoting, are silenced, a child may develop autism due to an underdevelopment of the social brain.
- If the father's genes are silenced, the effect could be a hyper-developed social brain, which is associated with schizophrenia.
"The most important aspect of the theory is that these sets of disorders can be seen as opposites to one another in the context of the development of the so-called human social brain," Crespi told CTV.ca in a phone interview from B.C.
Crespi began working on this theory after hearing Badcock speak about his theories that autism could be an opposite condition to schizophrenia.
Autism is a broad spectrum of disorders that is characterized by impaired social interaction and communication, while schizophrenia is characterized by a number of symptoms including paranoia, extreme activity and mood swings.
After looking into the genetic basis for each condition, as well as teaching himself the basics of psychiatry and psychology, "it became clear that there are imprinting effects in both of these, but they had not in the literature been considered in terms of evolutionary theory," Crespi said.
Crespi compiled data on the physiology and neurodevelopment of patients with both disorders, as well as information about psychological, cognitive and behavioural traits.
He looked for patterns in autistic patients, and then for the opposites in those with schizophrenia.
He found, for example, that smoking is far more common in patients with schizophrenia, while research has shown low rates of smoking in autism.
Crsepi is quick to caution that imprinting is only one of a number of contributing causes to both autism and schizophrenia, but it's one of the causes that most clearly demonstrates the opposite nature of the two conditions.
He also points out that the theory of the two disorders being opposites is a general one, that gene imprinting can have an impact on a number of diseases.
He says that while scientists know that the tug-of-war between the mother's and father's genes exists during fetal development, it is still unclear what exactly the imprinted genes are doing to the brain.
Crespi hopes his research will open up the field of psychiatry and the study of psychiatric disorders to include the study of evolutionary genetics.