Current research suggests there may be many factors involved in causing autism-related disorders.  A child’s risk of autism is thought to increase under the cumulative weight of various risk factors, so that a child’s genetic factors and the way in which he develops prenatally may make him more vulnerable to other factors.  These factors may include infectious illnesses, toxic substances (e.g., lead, methylmercury, PCBs, organophosphates, nicotine, and endocrine disrupters such as Dioxin), and factors that trigger active autoimmunity in genetically predisposed children, such as viral infections and vaccines.  Psychological or physical stress do not cause autism, but may contribute to a child’s difficulty relating and communicating.  For example, a child with extreme sensitivity to sensory information such as sound, touch and light, and with significant motor planning problems, can withdraw from relationships and become repetitive and self-stimulatory in a noisy and chaotic environment.