Psychopathy: The Substrate

Genes and brain: the biological foundations of psychopathy.This is the second article in a series on understanding psychopathy. The first article introduced the multi-level framework (G-N-E-D-B-A). This article covers the G (genetic) and N (neurological) levels – what you were born with and what your brain looks like now.Introduction When people ask “Is psychopathy genetic?” or “Is it in the brain?”, the answer is yes – but that’s not the whole story. Genetics and neurology form the substrate on which psychopathic presentations develop, but the substrate alone doesn’t determine the outcome. The same genetic loading can produce a successful surgeon or a convicted felon, depending on environment and development.This article covers what we know about the biological foundations of psychopathy, with an emphasis on a distinction that matters enormously for understanding prognosis and intervention: primary vs. secondary presentations.G-Level: Genetic ContributionsWhat We KnowPsychopathy has a heritable component. Twin studies suggest that callous-unemotional traits (a core feature of psychopathy) are moderately to highly heritable, with estimates ranging from 40% to 70% depending on the study and population. (See Viding et al., 2005, for an influential twin study.)However, “heritable” doesn’t mean “genetic” in a simple sense. Heritability estimates include gene-environment correlations and gene-environment interactions. A child with genetic loading for psychopathy may also be more likely to experience certain environments (because their parents, who share their genes, create those environments) – and the genes may only express under certain environmental conditions.Candidate GenesSeveral genes have been associated with psychopathic traits, though findings are often inconsistent and effect sizes are small. (See Gunter et al., 2010, Viding & McCrory, 2012, De Brito et al., 2021, and Frazier et al., 2019.)MAOA (Monoamine Oxidase A). The “warrior gene” – low-activity variants a