Are Mental Illnesses Inherited?

Abstract This is the first of three chapters dedicated to the causes of mental illness. It tackles the question of whether mental illnesses are inherited. In other words, this chapter covers the genetic contributions to mental illness. With many human traits, there is an age-old debate on whether the feature is driven by “nature” (genes) or “nurture” (environment). So this chapter focuses on the “nature” of mental illnesses. But no mental illness is entirely caused by nature. Instead, these illnesses all are due to a unique combination of genes and environmental factors. Thus, while this chapter focuses on the genes that put us at risk for mental illness, the chapter that follows will focus on those “nurture” factors in the environment that also make a contribution.