The Heritability of Mental Health Disorders: The Role of Heritability and Environmental Factors

Abstract

The purpose of this paper was to identify the degree of heritability of mental health disorders by examining the relationship between genetic predisposition and environmental triggers. We recruited fifty-five participants from five medical centers in Edo and Delta States of Nigeria, regardless of their gender or age, based on their predisposing family history of mental disorders. Prior to the study, these participants underwent a structured interview, a genetic vulnerability assessment using a specific polymorphism assay, and an environmental search. In view of this, it was ascertained that the estimated heritability of various mental disorders was: major depressive disorder (MDD) = 50–60%; bipolar disorder = 70–80%; schizophrenia = 60–70%; anxiety disorders = 30–40%; and attention-deficit/Hyperactivity disorder (ADHD) = 70–80%. Environmental conditions, childhood trauma, chemical use, the economic situation, living in large populations, and parents' mental health are among the factors that contribute to mental health disorders. Altogether, the work proved that genetic predispositions to mental health disorders bear equal responsibility in the development of the diseases, though it identified environmental factors as central in either enhancing or triggering these susceptibilities. This study provides clear evidence that mental health disorders are polygenic, and that research on the disorders should include both genetic and environmental aspects.