Etiology of Developmental Disorders: Good Science, Bad Science, and Pseudoscience

Developmental disorders originate in infancy or early childhood, are associated with presumed or observed organic abnormalities, and have serious long-term physical and/or psychological sequelae. Of particular interest here are two such disorders, mental retardation and autism. Purported causes range from genetics, early prenatal and/or postnatal exposure to toxins (including heavy metals), and recently, vaccinations. Single factors have often been claimed to be the cause of a developmental disorder, without regard to possible exacerbating or alleviating roles of other factors, including socioeconomic status. Unfortunately, professional and popular literature on both claimed causes and effective treatments has often been characterized by research and theorizing that is seriously flawed (bad science) or actively misrepresented (pseudoscience). The present paper critically reviews selected research on a few controversial issues concerning developmental disorders, particular mental retardation and autism, and emphasizes the role of low socioeconomic status.