Reacción a "The incidence of autism is similar in boys and girls, although boys are diagnosed earlier"

Traditionally, it has been assumed that autism spectrum disorder (ASD) is up to four times more common in boys than in girls. Multiple genetic and environmental factors have been suggested as possible causes for these differences. 

In a study recently published in The BMJ, researchers used national records to analyse autism diagnosis rates in 2.7 million people born in Sweden between 1985 and 2020, who were followed from birth to a maximum of 37 years of age. This study shows that boys are more likely to be diagnosed with autism during childhood (maintaining the ratio established in previous studies), while girls are diagnosed later during adolescence, reaching parity with boys by the age of 20. There are probably several reasons behind this late diagnosis in girls; on the one hand, their clinical manifestations may be more moderate or perhaps more easily overlooked, and on the other hand, we cannot rule out the existence of a gender bias in the diagnostic criteria for ASD, traditionally based on boys, which may have contributed to a lower diagnosis in girls.  

The importance and significance of this study lie not only in the enormous size of the population sample, which includes millions of people (albeit limited to Sweden), but also in its analysis of the effect of three different time scales: age at diagnosis, calendar period (year of diagnosis) and birth cohort. It should be noted that this is an observational study that did not consider other neurodevelopmental disorders associated with autism, such as attention deficit hyperactivity disorder and intellectual disability, nor did it take into account related genetic and environmental factors, such as parental age or complications during pregnancy.