Why more boys than girls diagnosed with autism?

Do you know that many females actions result to autism in their children before they conceive? Here is an article on how autism can be prevented during pregnancy and why more males have the deficiency than females. Though, girls may be better at hiding their difficulties, there is strong evidence to suggest that there are more boys with autism spectrum disorders (ASDs) than girls.



Autism is a lifelong developmental disability that affects how a person communicates with, and relates to, other people. It also affects how they make sense of the world around them. It is a spectrum condition, which means that, while all people with autism share certain difficulties, their condition will affect them in different ways. Some people with autism are able to live relatively independent lives but others may have accompanying learning disabilities and need a lifetime of specialist support. People with autism may also experience over- or under-sensitivity to sounds, touch, tastes, smells, light or colours.



Asperger syndrome is a form of autism. People with Asperger syndrome are often of average or above average intelligence. They have fewer problems with speech but may still have difficulties with understanding and processing language. Brugha (2009) surveyed adults living in households throughout England, and found that 1.8% of males surveyed had an ASD, compared to 0.2% of females.

Hans Asperger originally believed that no girls were affected by the syndrome he described in 1944, although clinical evidence later caused him to revise this statement. In Kanner's 1943 study of a small group of children with autism there were four times as many boys as girls. In their much larger study of Asperger syndrome in mainstream schools in Sweden in 1993, Ehlers and Gillberg found the same male to female ratio of 4:1. The ratio of male to females who use NAS adult services is approximately 4:1, and in those that use NAS schools it is approximately 5:1.


Wing (1981) found that among people with high-functioning autism or Asperger syndrome there were as many as 15 times as many males as females. On the other hand, when she looked at people with learning difficulties as well as autism the ratio of boys to girls was closer to 2:1. This would suggest that, while females are less likely to develop autism, when they do they are more severely impaired.

Why are more boys than girls diagnosed with autism?

Attwood (2000),Ehlers and Gillberg (1993) and Wing (1981) have all speculated that many girls with Asperger syndrome are never referred for diagnosis, and so are simply missing from statistics. This might be because the diagnostic criteria for Asperger syndrome are based on the behavioural characteristics of boys, who are often more noticeably "different" or disruptive than girls with the same underlying deficits.

Girls with Asperger syndrome may be better at masking their difficulties in order to fit in with their peers, and in general have a more even profile of social skills. Gould and Ashton-Smith (2011) say that because females with ASDs may present differently from males, diagnostic questions should be altered to identify some females with ASDs who might otherwise be missed.

Autism as an exaggeration of normal differences between the sexes

Another hypothesis (Wing 1981) is based on evidence that, in the general population, females have better verbal skills, while males excel in visuo-spatial tasks. There may be a neurological basis for this, so that autism can be interpreted as exaggeration of "normal" sex differences. But environmental and social factors may also play a part in sex differences in ability, which means that no direct analogy can be drawn between the poorer verbal skills of boys and the higher incidence of autism in males.



In 1964 Bernard Rimland pointed out that, overall, males tend to be more susceptible to organic damage than girls, whether through hereditary disease, acquired infection or other conditions. Since it is now almost universally accepted that there is an organic cause for autism, it should not be surprising that boys are more vulnerable to it than girls.


A genetic explanation for the difference

In recent years researchers have put forward a genetic explanation for the differences. Skuse (2000) has suggested that the gene or genes for autism are located on the X chromosome. Girls inherit X chromosomes from both parents, but boys only inherit one, from their mothers. Skuse's hypothesis is that the X chromosome which girls inherit from their fathers contains an imprinted gene which "protects" the carrier from autism, thus making girls less likely to develop the condition than boys.

This theory has been used to support Asperger's view that autism and Asperger syndrome are at the extreme end of a spectrum of behaviours normally associated with "maleness". Such behaviours can be extremely useful in areas of life such as engineering and science, where attention to detail and single-mindedness may be more valuable than social skills, for example.


Lord and Schopler (1987) have outlined several possible mechanisms for the transmission of autism on the sex-linked X chromosome, and also for autosomal transmission (ie involving non-sex chromosomes. However, these are merely theoretical models and in fact researchers are still a long way from identifying a simple genetic cause for autism. It is likely that several genes on different chromosomes will be found to be associated with autism. This means that Skuse's theory, based on the X chromosome alone, may not represent the full picture. Various theories have been put forward for the excess of males with autism and Asperger syndrome, but the picture is far from complete and until we have a fuller understanding of the causes of autism, it is unlikely that a proper explanation can be reached.



Avoiding Autism During Pregnancy

We know that environmental factors – including exposure to certain toxic substances during pregnancy – can increase the risk of autism. It’s important to distinguish increased risk from cause. In most cases, autism results from multiple factors in addition to genetic predisposition. These can include a pregnant woman’s exposure to certain chemicals such as pesticides and phthalates (commonly found in plastics) and certain drugs such as terbutaline (used to stop premature labor), valproic acid (to control seizures) and some antipsychotics and mood stabilizers.


Importantly, in the case of medications, any possible increased risk of autism must be balanced against a woman’s medical needs. Remember, your health can likewise affect your pregnancy and the health of future children. We have much more to learn about the environmental factors that increase autism risk. And we can’t say that avoiding one particular exposure means reducing risk of ASD for a particular individual. However, we know that exposure to certain toxic substances is associated with increased risk for a number of developmental disorders. So we can recommend some practical, protective steps that women can take before or during pregnancy to these exposures.


Recommendations to consider if you’re pregnant or trying to conceive:

The American College of Obstetricians and Gynecologists, the Royal College of Obstetricians and Gynecologists and other authorities endorse the following recommendations:

1. Discuss medications with your healthcare provider. In particular, discuss risks associated with terbutaline, valproic acid (valproate), over-the-counter painkillers, prenatal vitamins, antipsychotics and mood stabilizers.


2. Ask your doctor about folic acid. Research suggests that folic acid supplements – taken before and during pregnancy – reduce the risk of autism.


3. Avoid cigarette smoke and alcohol. Both can have adverse effects on fetal development as well as long-term health of both mother and child.


4. Eat plenty of fresh produce, but wash it before eating. Eating plenty of fresh, unprocessed fruit and vegetables is highly recommended during pregnancy. Just be sure to wash thoroughly to reduce possible pesticide or microbial contamination.


5. Cut down on packaged foods. Some packaged foods – such as microwave/oven-ready meals – leach chemicals into food. These chemicals can include endocrine-disrupting chemicals such as BPA and phthalates. In particular, avoid plastics with the recycling codes #3, #4 and #7.


6. Eliminate or limit to once a week your consumption to oily fish and tuna. Oily fish can accumulate dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyls (PCB) in their fat tissues. Certain other fish such as tuna tend to accumulate mercury and lead.


7. Limit your use of personal care products (moisturizers, body wash, perfume, etc.) with strong scents and artificial ingredients. Visit this Parents.com webpage for some creative “safer swaps” such as fragrance-free products.

8. While pregnant or breastfeeding, reduce or avoid your exposure to fumes from new household furniture, fabrics, non-stick frying pans and cars; pesticides, fungicides, fresh paint or solvents.  Avoiding these products will reduce your exposure to potentially toxic chemicals such as perfluorinated compounds (PFCs).

9. Remember that “natural” doesn’t necessarily mean safe during pregnancy. This is particularly true of over-the-counter “alternative” medications and supplements. Few have been tested for safety during pregnancy.


10. Fill out an environmental exposure history questionnaire and bring it to your health care provider:



In our next edition, we will be discussing the facts and myths about autism. Kindly send your comments and suggestions to This email address is being protected from spambots. You need JavaScript enabled to view it.


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