Parents of children with autism usually have a few unanswered questions such as "How did my child develop autism?" "My child was absolutely fine and had even started to pick up a few words. What happened all of sudden?" "Is autism acquired?" "Could it have been prevented?" "Is it genetic?" "Can my other children also have autism?"
Medical science does not have answers for many of these questions, and although the "why" may never be known, what is becoming clearer with ongoing research is, "What is the fundamental problem in the brains of the children with Autism".
In autism, though the brain structure looks normal, there are functional abnormalities in speciﬁc regions of brain. This information, about the functioning of brain areas can be obtained from functional neuroimaging techniques like PET-CT scan and functional MRI scan of the brain. These imaging studies permit the study of the abnormal pattern of cortical activation in autism. These studies indicate that certain areas of the brain show reduced functioning like mesial temporal lobe (innermost part of the brain responsible for learning, understanding, memory, social interaction and abstract thinking), frontal lobe (the front part of the brain responsible for emotions and aggression) and cerebellum (responsible for balance, coordination, muscle tone and speech). Hence the dysfunction of these areas are responsible for problems seen in autism.
Positron Emission Tomography – Computed Tomography Scans showing areas of brain with reduced function
Research has also helped us to know that there isn’t one cause of autism but multiple risk factors that increase the risk of a child developing autism. Most cases of autism seem to be caused by a combination of autism risk genes and environmental factors influencing the early brain development. Over the last five years, scientists have identified a number of rare gene changes or mutations which have been associated with autism. Other factors related to children with autism and their parents that may contribute to increase the risk of Autism have also been identified. Along with these certain environmental factors have also been included in the risk factors for Autism.
Below mentioned are a few probable causes of autism:
Patient and family related factors:
Environmental factors play a role in increasing risk of Autism. With urbanization and industrialization we are exposed to chemical pollutants in air, water, soil and therefore even the food we eat. With advent of technology we are exposed to more and more electromagnetic radiations. These elements are presumed to contribute to increased risk of Autism.
1. Gastrointestinal flora and gastrointestinal status in children with autism-comparisons to typical children and correlation with autism severity. Adams JB, Johansen LJ, Powell LD, Quig D, Rubin RA BMC Gastroenterol. 2011 Mar 16; 11:22.
2. Normal gut microbiota modulates brain development and behavior. Heijtz, R. D., Wang, S., Anuar, F., Qian, Y., Björkholm, B., Samuelsson, A., … Pettersson, S. (2011). Proceedings of the National Academy of Sciences of the United States of America, 108(7), 3047–3052.
3. Impaired Carbohydrate Digestion and Transport and Mucosal Dysbiosis in the Intestines of Children with Autism and Gastrointestinal Disturbances. Williams, B. L., Hornig, M., Buie, T., Bauman, M. L., Cho Paik, M., Wick, I., … Lipkin, W. I. (2011). PLoS ONE, 6(9), e24585.
4. Biological plausibility of the gut-brain axis in autism. Vasquez A. Ann N Y Acad Sci. 2017 Nov;1408(1):5-6
5. Galuska L, Szakáll Jr S, Emri M, Oláh R, Varga J, Garai I, Kollár J, Pataki I, Trón L. PET and SPECT scans in autistic children. Orvosihetilap. 2002 May;143(21 Suppl 3):1302-4.
6. Chugani DC, Muzik O, Behen M, Rothermel R, Janisse JJ, Lee J, Chugani HT. Developmental changes in brain serotonin synthesis capacity in autistic and nonautistic children. Annals of neurology. 1999 Mar 1;45(3):287-95.
7. Schifter T, Hoffman JM, Hatten JR HP, Hanson MW, Coleman RE, DeLong GR. Neuroimaging in infantile autism. Journal of Child Neurology. 1994 Apr;9(2):155-61.
8. Mountz JM, Tolbert LC, Lill DW, Katholi CR, Liu HG. Functional deficits in autistic disorder: characterization by technetium-99m-HMPAO and SPECT. Journal of Nuclear Medicine. 1995 Jul 1;36(7):1156-62.
9. Zürcher NR, Bhanot A, McDougle CJ, Hooker JM. A systematic review of molecular imaging (PET and SPECT) in autism spectrum disorder: current state and future research opportunities. NeurosciBiobehav Rev. 2015 May;52:56-73.
10. Wang C, Geng H, Liu W, Zhang G. Prenatal, perinatal, and postnatal factors associated with autism: A meta-analysis. Medicine (Baltimore). 2017 May;96(18):e6696
11. Modabbernia A, Velthorst E, Reichenberg A. Environmental risk factors for autism: an evidence-based review of systematic reviews and meta-analyses. Mol Autism. 2017 Mar 17;8:13
12. Wakefield AJ, Murch SH, Anthony A, Linnell J, Casson DM, Malik M, Berelowitz M, Dhillon AP, Thomson MA, Harvey P, Valentine A. RETRACTED: Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children.
13. Plotkin S, Gerber JS, Offit PA. Vaccines and autism: a tale of shifting hypotheses. Clinical Infectious Diseases. 2009 Feb 15;48(4):456-61.