The question of whether the prevalence increase observed in autism due to an actual increase in the incidence of autism is a matter of concern to professional psychologists, and has been a matter of debate. As professionals trained in diagnosis and research methodology, the opinions of psychologists are of interest. We report the results of what we believe to be the first survey of professional opinion on the topic. Results suggest that among professional psychologists with a terminal degree (n = 88), the majority believe that diagnostic changes can not fully account for the observed increase; 72% reported either the true rate may have, or definitely has, increased. In this sample, the professionals who are certain about the occurrence of a real increase (n=20) are five times as many as those who do not think the increase has occurred (n=4). These results are not meant to document whether or not an increase has or has not occurred, but instead speak to the question of consensus opinion among professional psychologists. What experts believe is an empirical question, and statements about what experts believe should be empirically based.
Cite this paper
DeSoto, M. and Hitlan, R. (2013) Professional opinion on the question of changes in autism incidence. Open Journal of Psychiatry, 3, 61-67. doi: 10.4236/ojpsych.2013.32A010.
 Centers for Disease Control Autism and Developmental Disabilities Monitoring Network (2009) Prevalence of autism spectrum disorders—Autism and developmental disabilities monitoring network, United States, 2006. Morbidity and Mortality Weekly Report, 58, SS-10.
 Fombonne, E. (2003) The prevalence of autism. Journal of the American Medical Association, 289, 87-89.
 Wazana, A., Breshnahan, M. and Kline, J. (2007) The autism epidemic: Fact or artifact? Journal of the American Academy of Child and Adolescent Psychiatry, 46, 721-730. doi:10.1097/chi. 0b013e3 1804a7f3b
 Merrick, J., Kandel, I. and Morad, M. (2004) Trends in autism. International Journal of Adolescent Medicine and Health, 16, 75-78. doi:10.1515/IJAMH.2004.16.1.75
 Gillberg, C., Cederlund, M., Lamberg, K. and Zeijlon, L. (2006) The autism epidemic: The registered prevalence of autism in a Swedish urban area. Journal of Autism and Developmental Disorders, 36, 429-435.
 Atladottir, H.O., Schendel, D., Dalsgaard, S., Thomsen, P.H. and Thorsen, P. (2007) Time trends in reported diagnoses of childhood neuropsychiatric disorders: A Danish cohort study. Archives of Pediatrics and Adolescent Medicine, 161, 193-199. doi:10.1001/archpedi.161.2.193
 Hallmayer, J. et al. (2011) Genetic heritability and shared environmental factors among twin pairs with autism. Archives of General Psychiatry, 68, 1095-1102.
 Lawler, C.P., Croen, L.A., Grether, J.K. and Van de Water, J. (2004) Identifying environmental contributions to autism: Provocative clue and false leads. Mental Retardation and Developmental Disabilities Research Review, 10, 292-302. doi:10.1002/mrdd.20043
 Palmer, R., Wood, S. and Blanchard, R. (2008) Proximity to point sources of environmental mercury release as a predictor of autism. Health Place, 15, 18-24.
 DeSoto, M.C. (2009) Ockham’s razor and autism: The case for developmental neurotoxins contributing to a disease of neurodevelopment. Neurotoxicology, 30, 331-337.
 Eskanzi, B., Marks, A.R., Bradman, A., Harley, K., Barr, D.B., Johnson, C., et al. (2007) Organophosphate pesticide exposure and neurodevelopment in young MexicanAmerican children. Environmental Health Perspectives, 115, 792-798. doi:10.1289/ehp.9828
 Tamm, C., Duckworth, J., Hermanson, O. and Ceccatelli S. (2006) High susceptibility of neural stem cells to methylmercury toxicity: Effects on cell survival and neuronal differentiation. Journal of Neurochemistry, 97, 69-78. doi:10.1111/j.1471-4159.2006.03718.x
 Stern, A.H. and Smith, A.E. (2003) An assessment of the cord blood: Maternal blood methylmercury ratio: Implications for risk assessment. Environmental Health Perspectives, 111, 1465-1470. doi:10.1289/ehp.6187
 Morissette, J., Takser, L., St-Amour, G., Smargiassi, A., Lafond, J. and Mergier, D. (2004) Temporal variation of blood and hair mercury levels in pregnancy in relation to fish consumption history in a population living along the St. Lawrence River. Environmental Research, 95, 263-274. doi:10.1016/j.envres.2003.12.007
 Ip, P., Wong, V., Ho, M., Lee, J. and Wong, W. (2004) Mercury exposure in children with autistic spectrum disorder: Case-control study. Journal of Child Neurology, 19, 431-434.
 DeSoto, M.C. (2008) A reply to Soden: Your data shows autistic children have higher levels of heavy metals. Clinical Toxicology, 46, 1098.
 Brumback, R. (2007) Note from editor-in-chief about erratum for Ip et al. article. Journal of Child Neurology, 22, 1321. doi:10.1177/0883073807308149
 DeSoto, M.C. and Hitlan, R.T. (2007) Blood levels of mercury are related to diagnosis of autism: A reanalysis of an important data set. Journal of Child Neurology, 22, 1308-1311. doi:10.1177/08830 73807307111
 Latif, A.H.A. and Williams, W.R. (2007) Diagnostic trends in autistic spectrum disorder in South Wales valleys. Autism, 11, 479-487.
 Fitzgerald, M. (2007) Autism and environmental toxicity. Lancet Neurology, 6, 297.
 Babbie, E. (2007) The practice of social research. 11th Edition, Thompson Wadsworth, Belmont.
 Edelson, S.B. and Cantor, D. (2000) The neurotoxic etiology of the autistic spectrum disorders: A replication study. Toxicology and Industrial Health, 16, 239-247.
 Nataf, R., Skorupka, C., Amet, L., Lam, A., Springbett, A. and Lathe, R. (2006) Porphyrinuria in childhood autistic disorder: Implications for environmental toxicity. Toxicology and Applied Pharmacology, 214, 99-108.
 Geier, D.A. and Geier, M.R. (2006) A prospective assessment of porphyrins in autistic disorders: A potential marker for heavy metal exposure. Neurotoxicology Research, 10, 57-64. doi:10.1007/ BF03033334
 Hoshino, Y., Tachibna, Y., Watanabe, H., Kumashiro, R. and Yashima, M. (1982) The epidemiological study of autism Fukushima-Ken. Folia Psychiatric Neurology Japan, 36, 115-124.
 Oliveira, G., Ataíde, A., Marques, C., Miguel, T.S., Coutinho, A.M., Mota-Vieira, L., Goncalves, E., Lopes, N.M., Rodrigues, V., Carmona da Mota, H. and Vicente, A.M. (2007) Epidemiology of autism spectrum disorder in Portugal: Prevalence, clinical characterization, and medical conditions. Developmental Medicine and Child Neurology, 10, 726-733. doi:10.1111/j.1469-8749.2007.00726.x
 Kamer, A., Diamond, R., Inbar, Y., Zohar, G.W., Youngmann, D. and Senecky, A.H. (2004) A prevalence estimate of pervasive delopmental disorder among immigrants to Israel and Israel natives—A file review study. Social Psychiatry and Psychiatric Epidemiology, 39, 141-145.
 Barnevik-Olsson, M., Gillberg, C. and Fernell, E. (2008) Prevalence of autism in children born to Somali parents living in Sweden: A brief report. Developmental Medicine and Child Neurology, 50, 598-601.
 Windham, G.C., Zhang, L., Gunier, R., Croen, L.A. and Grether, J.K. (2006) Autism spectrum disorders in relation to distribution of hazardous air pollutants in the San Francisco Bay Area. Environmental Health Perspectives, 114, 1438-1444. doi:10.1289/ehp.9120
 Roberts, E.M., English, P.B., Grether, J.K., Windham, G.C., Somberg, L. and Wolff, C. (2007) Maternal residence near agricultural pesticide applications and autism spectrum disorders among children in the California Central Valley. Environmental Health Perspectives, 115, 1482-1489.
 Volk, H.E., Hertz-Picciotto, I., Delwiche, L., Lurmann, F. and McConnell, R. (2011) Residential proximity to freeways and autism in the CHARGE study. Environmental Health Perspecives, 119, 873-877.
 DeSoto, M.C. and Hitlan, R.T. (2012) Fish consumption advisories and the surprising relationship to prevalence rate of developmental disability as reported by public schools. Journal of Environmental Protection, 3, 1579-1589. doi:10.4236/jep.2012.311174