[Reflections of a geneticist on the influence of genes in psychiatric disorders]

The nature and causes of psychiatric disorders are controversial and subject to debate, with theories changing according to historical, scientific, political, social and cultural contexts. In the past, hereditarian hypotheses stumbled in front of the lack of knowledge of genetics, the complexity of genetic-environmental interactions and the controversies of phenotypic definitions, still unresolved. The burst of genomics gave hopes to those who believe that the causes of psychiatric disorders is in the genes and who, armed with DNA sequencers and bioinformatics, began comparing genomic sequences among patients and controls, looking for associations with diverse phenotypes which remain inadequately defined. Given that all human characteristics are influenced by genes, the predictable is happening: an endless stream of associations with hundreds of genes, albeit with few causal clues. All human characteristics are also influenced by environmental/social factors, which explain even more of the phenotypic variance of psychiatric conditions. Given that methods for the study of those, and their interaction with the genome, are not as advanced as genomics, the understanding of causalities of mental disorders is in a labyrinth, from which it will only emerge with new approaches to genetic-environmental interactions that go beyond epigenomics and focus on not necessarily chemically measurable influences.