These risk factors include maternal gestational diabetes, maternal and paternal age over 30, bleeding during pregnancy after the first trimester, use of certain prescription medication (e.g. valproate) during pregnancy, and meconium in the amniotic fluid. While research is not conclusive on the relation of these factors to autism, each of these factors has been identified more frequently in children with autism, compared to their siblings who do not have autism, and other typically developing youth. While it is unclear if any single factors during the prenatal phase affect the risk of autism, complications during pregnancy may be a risk.Low vitamin D levels in early development have been hypothesized as a risk factor for autism.There are also studies being done to test if certain types of regressive autism have an autoimmune basis.Maternal nutrition and inflammation during preconception and pregnancy influences fetal neurodevelopment. Intrauterine growth restriction is associated with ASD, in both term and preterm infants. Maternal inflammatory and autoimmune diseases may damage fetal tissues, aggravating a genetic problem or damaging the nervous system.Exposure to air pollution during pregnancy, especially heavy metals and particulates, may increase the risk of autism. Environmental factors that have been claimed without evidence to contribute to or exacerbate autism include certain foods, infectious diseases, solvents, PCBs, phthalates and phenols used in plastic products, pesticides, brominated flame retardants, alcohol, smoking, illicit drugs, vaccines, and prenatal stress. Some, such as the MMR vaccine, have been completely disproven.
In the 1950s, the refrigerator mother theory emerged as an explanation for autism. The hypothesis was based on the idea that autistic behaviors stem from the emotional frigidity, lack of warmth, and cold, distant, rejecting demeanor of a childs mother. Parents of children with an ASD experienced blame, guilt, and self-doubt, especially as the theory was embraced by the medical establishment and went largely unchallenged into the mid-1960s. The "refrigerator mother" theory has since continued to be refuted in scientific literature, including a 2015 systematic review which showed no association between caregiver interaction and language outcomes in ASD. Another controversial claim suggested that watching extensive amounts of television may cause autism. This hypothesis was largely based on research suggesting that the increasing rates of autism in the 1970s and 1980s were linked to the growth of cable television at this time. Terminology and distinction from schizophrenia
As late as the mid-1970s there was little evidence of a genetic role in autism, however by 2007 it was recognised as one of the most heritable psychiatric conditions. Although the rise of parent organizations and the destigmatization of childhood ASD have affected how ASD is viewed, parents continue to feel social stigma in situations where their childs autistic behavior is perceived negatively, and many primary care physicians and medical specialists express beliefs consistent with outdated autism research.It took until 1980 for the DSM-III to differentiate autism from childhood schizophrenia. In 1987, the DSM-III-R provided a checklist for diagnosing autism.