In this review, we give an overview of psychiatric perspectives on environmental disease. The concept of genetic heritability and its meaning with regard to environmental risk factors will be discussed. Recent ideas of gene-environment interaction and neurodevelopmental disorder in psychiatry will also be introduced. This article discusses the environmental risk factors for attention deficit hyperactivity disorder (ADHD) and autism, the two major environmental diseases and neurodevelopmental disorders in psychiatry. Given that both ADHD and autism are complex conditions, the etiology is likely to involve multiple genes of moderate effect interacting with environmental factors. We will introduce recent environmental issues related to these two disorders.