A study conducted by researchers at the University of Bristol in the UK has found a correlation between a child’s Autism Spectrum Disorder (ASD) diagnosis and their maternal grandmother’s smoking habits.
The correlation was observed in a group of 14,500 children born in the 1990s. The risk of a child being diagnosed with ASD is increased by 53 percent if their maternal grandmother smoked.
Furthermore, the impact of the maternal grandmother’s smoking on the grandchild is stronger in girls. The study found that girls are 67 percent more likely to present symptoms of autism, such as poor social communication skills and repetitive behavior, than boys are.
Autism spectrum disorder is a developmental disorder that can impair an individual’s ability to communicate and interact with others. It is a commonly diagnosed disorder, with more than 200,000 cases per year in the US alone. ASD is a chronic disorder with treatable symptoms but is unable to be cured. The number of diagnoses has been increasing over recent years, which can be attributed to improved detection and epigenetic factors such as smoking.
Because of its prevalence, a slew of inaccurate potential causes of autism have been brought forth. Most notably, proponents of the anti-vaccine movement have pointed fingers at child immunizations. If the correlation observed in this study between smoking and autism is found to be true causation, more research will be conducted into how smoking effects both nuclear and mitochondrial DNA in developing embryos.
Professor Marcus Pembrey, an author on the paper published in Scientific Reports, cites two broad possible mechanisms by which grand-maternal smoking can lead to autism in a child. Pembrey states, “There is DNA damage that is transmitted to the grandchildren or there is some adaptive response to the smoking that leaves the grandchild more vulnerable to ASD.”
The DNA damage that Pembrey is talking about is primarily in the mitochondria. Mitochondrial DNA is passed from mother to child, so mutations caused by smoking can directly impact the child. He further states, “The initial mitochondrial DNA mutations often have no overt effect in the mother herself, but the impact can increase when transmitted to her own children.”
This study has heavy implications. Alycia Halladay, the chief science officer at the Autism Science Foundation, stated, “To date, research into the causes of autism has been limited to studying maternal or paternal exposures during pregnancy.” With the results of this study, correlation between autism and smoking are made beyond the immediate generation. Smoking could not only impact your children, but also your grandchildren. Dr. Dheeraj Raj, another author of the paper, states, “We still do not know why many children develop autism and behaviors linked to it. The associations we observe raise intriguing issues on possible transgenerational influences in autism.”
The authors of the study admit that the discrepancy between ASD diagnosis and gender cannot be explained at the moment. Further research must be done to elucidate the developmental differences that smoking has on each gender, as well as the mechanism by which smoking leads to intergenerational genetic disorders.
Source: Golding, J. et al. Grandmaternal smoking in pregnancy and grandchild’s autistic traits and diagnosed autism. Sci. Rep. 7, 46179