Autistic traits more common in girls if their grandmothers smoked during pregnancy

The health hazards of smoking are well known; heart disease, stroke, diabetes, cancer , the list goes on… Can we add Autism? A new study has found a link between grandmothers smoking during pregnancy and their granddaughters showing signs of Autism, or “Autistic traits”.

What is Autism?

Autism is a complex condition which affects how people see the world around them and interact with others.  There are actually a group of similar conditions of varying severity known as “Autism Spectrum Disorders” or ASD.  Autism is a form of ASD and is most commonly diagnosed in childhood.

There are several signs or “traits” people with ASD display.  These include difficulties in social situations with problems understanding and recognising other people’s emotions. They often prefer to spend time alone and may have trouble maintaining friendships. Communication is also difficult, they have problems expressing what they want to say and interpreting other people’s facial gestures. As children, they may lack the ability to play imaginative, make-believe games and will play the same games repeatedly. They can have obsessive interests in unusual subjects, such as train timetables or car number plates.  They may display repetitive behaviors such as flapping their hands.

The range of difficulties an individual experience varies widely, some people can function very independently. Others need specialist care and help with daily life. They may have other learning disabilities, or mental health problems including ADHD. At the other end of the spectrum, people with Asperger Syndrome, may be extremely intelligent (think Sheldon Cooper from the Big Bang Theory!*). Currently, we don’t know what causes ASD, but it is thought to be due to a combination of genetic and environmental factors.

About the Study

Researchers at the University of Bristol looked at data collected from 14,500 children who were participants in the in Children of the ’90s study.   They examined whether the children displayed autistic traits, such as poor communication skills, and if their grandmothers smoked whilst pregnant.  They found that girls were more likely to show these traits if their maternal grandmother had smoked during pregnancy. Interestingly, this was only the case if the girl’s own mothers had NOT smoked during their own pregnancy.  There was no association with grandsons, although the reasoning behind this sex difference is still not clear.  It should be noted that these girls only showed an increase in displaying some of the symptoms, or traits, of ASD, and the link with an actual Autism diagnosis was much weaker.

The Science Behind the Findings

So how can smoking whilst pregnant increase the chances of your granddaughter showing Autistic traits? Scientists are not 100% sure of the cause, but they have a theory. We already know smoking damages DNA, and this causes changes to our cells. The theory here is that smoking corrupts the DNA in cells called mitochondria, which are passed on to children via mothers’ eggs.  So, if a female is exposed to cigarette smoke whilst a fetus in the womb, her developing eggs are damaged by this corrupted DNA. These changes may then affect her own children. What is not clear, however, is why grandsons appear unaffected by these changes.

In Summary

It is impossible to tell whether the smoking habits of a grandmother was the only cause for these increased rates of Autistic traits. The study contained a large volume of information and there are many differences between the families which took part. For example, each family would have different diets, genetic make-up, parental alcohol intake, exercise levels, which could all play a role too. However, one thin is clear, this research is another reason to put those cigarettes away when pregnant. In the meantime, the jury is out.

For more information on Autism, and support click here.
For further advice on smoking in pregnancy click here.

Related article “Grandmothers can spot Autism”

*The creators of the Big Bang Theory have never confirmed that their character Sheldon Cooper has a diagnosis of Asperger Syndrome, nor is it mentioned in the show. However, it is a popular fan theory that Sheldon is “on the spectrum” and his character at times shows some of the common traits.’

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Any opinions above are the author’s alone and may not represent those of his/her affiliations. Any comment is based on the best available evidence at the time of writing.  All data is based on externally validated studies unless expressed otherwise. Novel data is representative of the sample surveyed. An online recommendation is no substitute for seeing your own doctor and should not be taken as medical advice.

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About hannaharnstein (13 Articles)
I am a psychiatry trainee working in the North East, but currently on maternity leave. Outside of medicine, other than writing I enjoy all things geek, baking and reading.

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