Autism Causes

It is possible to develop autism with or without the risk factors listed below. However, the more risk factors you have, the greater your likelihood of developing autism. There is no way known to modify your child's risk for autism.

Genetic Factors

Genetics is believed to play a role in the risk of autism because the condition is more common in:

• Families
• Identical twins

Recent studies have linked deletions in a section of chromosome 16. This chromosome abnormality may account for a small percentage of autism cases.

Gender

Caucasian males are more likely to be affected by autism than females. When girls are affected, though, they may have more profound symptoms.

Age of Parents

Older parents (eg, mother's age over 35) may have a higher risk of having a child with autism.

Medical Conditions

Autism occurs more frequently in children with rare genetic disorders or other medical conditions, including:

• Tuberous sclerosis—A rare, multi-system genetic disease that causes benign tumors to grow in the brain and on other vital organs such as the kidneys, heart, eyes, and skin. It commonly affects the central nervous system and results in a combination of symptoms including seizures, developmental delay, behavioral problems, skin abnormalities, and kidney disease.
• Fragile X syndrome —A hereditary disorder of the X chromosome. It is the most common cause of inherited mental retardation.
• Neurofibromatosis —A genetic disorder of the nervous system. It causes tumors to grow on the nerves in any part of the body. Neurofibromatosis can also produce other abnormalities, such as changes in the skin and deformed bones.
• Phenylketonuria (PKU) —A genetic disorder of the enzyme that breaks down phenylalanine, which is an amino acid found in certain foods. Without a proper diet, PKU can lead to intellectual disability.
• Problems during pregnancy or delivery, including rubella. —Rubella is a mild, highly contagious illness that is caused by a virus. It is characterized by a rash, swollen glands, and joint pain. If a pregnant woman has rubella, it can cause birth defects in her baby. Other possible risk factors include breech delivery and birth at less than 35 weeks gestation.
• Epilepsy —The term “epilepsy” refers to any disorder characterized by recurrent seizures. During a seizure, you may lose consciousness, stare into space, have convulsions (abnormal jerking of the muscles), or experience abnormalities of sensation or emotion.
• Tourette’s syndrome
• Newborn encephalopathy—This is a syndrome of disturbed brain function that includes breathing difficulties, problems with reflexes, seizures, and other symptoms.
• Moebius syndrome, cytomegalovirus, herpes encephalitis—These are sometimes listed as associated conditions.
• Birth defects—Birth defects may also predispose a child to developing autism.
• ADD/ADHD - 31% of children with autism also meet diagnostic criteria for ADHD
• Maternal dysbiosis - During childbirth, beneficial bacteria are passed from mother to child. These bacteria are the building blocks of both the digestive and the immune system. A link has been observed between an imbalance in gut flora in mothers and the presence of autism in children. It is known as Gut and Psychology Syndrome, or GAPS.

There has also been a lot of press attention claiming links between vaccines and autism, as well as growing concern about high fructose corn syrup (HFCS) and its possible causal role. Fetal and early childhood mercury exposure have also been linked to autism.

• Autism and Vaccines
• Autism and High Fructose Corn Syrup (HFCS)
• Autism and Mercury Exposure

References:

Autism spectrum disorders (pervasive developmental disorders). National Institute of Mental Health (NIMH) website. Available at: http://www.nimh.nih.gov/health/topics/autism-spectrum-disorders-pervasive-developmental-disorders/index.shtml . Updated April 2008. Accessed September 11, 2008.

Autism Society of America. Autism 101 course. Autism Society of America website. Available at: http://www.autism-society.org/site/PageServer?pagename=about_course . Accessed June 15, 2010.

Behrman RE, et al. Nelson Textbook of Pediatrics. 18th ed. Philadelphia: Saunders, 2007.

DynaMed Editorial Team. Autistic disorder. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php . Updated September 13, 2010. Accessed September 14, 2010.

Dufault, Renee, et al. "A Macroepigenetic approach to identify factors responsible for the autism epidemic in the United States". Clinical Epigenetics 4, no. 6 (10 April 2012).

Goetz CG. Goetz’s Textbook of Clinical Neurology.3rd ed. Philadelphia, PA: Saunders; 2007.

Jacobson JL, Jacobson AM. Psychiatric Secrets. 2nd ed. Philadelphia, PA: Hanley & Belfus, 2001.

National Center on Birth Defects and Environmental Disabilities. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/ncbddd/ . Accessed June 23, 2008.

Neonatal encephalopathy. Newborn Services Clinical Guideline website. Available at: http://www.adhb.govt.nz/newborn/guidelines/Neurology/NE.htm . Updated November 2004. Accessed June 16, 2010.

Rapin I. An 8-year-old boy with autism. JAMA. 2001;285:1749-1757.

Stern TA, et al. Massachusetts General Hospital Comprehensive Clinical Psychiatry. 1st ed. Philadelphia, PA: Mosby Elsevier; 2008.

Parker SK, Schwartz B, Todd J, Pickering LK. Thimerosal-containing vaccines and autistic spectrum disorder: a critical review of published original data. Pediatrics.2004;114(3):793-804.

Wilson K, Mills E, Ross C, McGowan J, Jadad A. Association of autistic spectrum disorder and the measles, mumps, and rubella vaccine: a systematic review of current epidemiological evidence. Arch Pediatr Adolesc Med.2003;157(7):628-634.