For the first time in history, scientists have found two genetic variants linked to major depression disorder (MDD). The study, published in Nature, has been received with mixed feelings respect to its relevance. The two loci variants, located in chromosome 10, cause people a 1% increase of risk of developing MDD.
Depression is one of the most common mental illnesses and the leading cause of disability worldwide. Finding a genetic element in depression would be very useful to fight the disorder. Many molecular techniques can be applied to regulate the target locus once it is defined. Qi Xu, Jun Wang,Kenneth S. Kendler and Jonathan Flint analyzed the genome of more than 10000 Chinese women, half of which suffered from MDD. They identified two variants of the genes SIRT1 and LHPP that were more frequent in the sick group. The results could not be replicated in European women, probably due to the lower frequency of those variants in European humans respect to Asian population.
Other scientists like David Cutler from Emory University are unconvinced of the relevance of this study. Cutler claims the effect is borderline significant at best and that the authors only studied 12 genes in the replication study they executed.
Further studies will have to be performed to clarify the effect of the two variants, extending the tests to men and to other world populations.