Advances in molecular genetics and gene wide association studies have been a strong force in the identification of phenotype and genetic predictors for psychosis. The link between genetics and diseases is not limited to psychosis. In fact, genes are major predictors of a wide range of pathological conditions and the association of genes and diseases remains the major factor for the determination of the etiology of diseases. Some studies suggest that a substantial proportion of genetic risk factors for MD appeared to be shared in men and women. For instance, epidemiological studies of major depression have consistently shown a higher prevalence rate for women
Currently, there are eighteen (18) most studied genes in the field of mental health, and that single gene variants, or even a small group of them, can dictate susceptibility to depression. One of the 18 “historic candidate depression genes” is SLC6A4 which codes for a protein that is involved in the transport and recycling of serotonin, a molecule that is associated with depression in the brain.
About two decades ago, scientists have earlier suggested that having a particular, shorter variant of SLC6A4 could put people at greater risk for depression, especially if they had experienced trauma during childhood.
However, this notion was recently debunked. Scientists now think differently about the genetic basic in the etiology of depression. They now believe that any genetic risk for depression likely arises from very large numbers of variants, each contributing a small effect. Scientists at the University of Colorado Boulder (CU Boulder) conducted the study through a review of hundreds of investigations that, over the last 25 years, had singled out “candidate genes” for depression. They discovered that 18 such genes had featured at least 10 times in previous studies. The scientists picked at random, data from hundreds of thousands of people. They discovered that the influence the 18 candidate genes had on depression was no stronger than that of genes they could pick out at random.
The study involved the use of both genetic and survey data for 620,000 people, focused on 18 candidate genes mentioned in at least 10 previous studies. Researchers investigated whether any of the genes or gene variants were linked with depression either alone or combined with environmental factors such as childhood trauma or socioeconomic diversity.
“This study confirms that efforts to find a single gene or handful of genes which determine depression are doomed to fail.” Says Richard Border, a researcher and graduate student in CU Boulder’s Institute for Behavioral Genetics.
The findings of this research do not mean that genetics has no role to play in depression. In fact, it does. “We are not saying that depression is not heritable at all. It is. What we are saying is that depression is influenced by many, many variants, and individually each of those has a minuscule effect.” Says Matthew C. Keller Ph.D. “It’s like in The Emperor Wears No Clothes,” Dr. Keller added. “There’s just nothing there.”