Please note that this post refers frankly to biological functions and reproductive development.
Wait. What?! What does that title have to do with media and AS? Trust me.
Melatonin is a hormone that the human body generates in darkness. It regulates a variety of biological functions, including circadian rhythms, and seems to be involved in immune function. A growing body of research seems to show that melatonin is also involved in the reproductive system--both its maturation and its functioning.
A current issue of concern for doctors in the US is the fact that the number of girls entering puberty prematurely has increased steadily over the last century. However, the cause(s) remain uncertain. What is known is that early sexual development (defined either as the beginning of of breast tissue development by age of 7 or menarche occurring before the age of 12) increases the likelihood of a girl engaging in risky behaviors (by choice or otherwise) and, more disturbingly, raises her risk of developing breast cancer later in life.
A recent metastudy (drawing on data from 35 individual studies) noted that the light emitted from television screens is of a type that inhibits melatonin production.
While some research also suggests a link between melatonin levels and autism spectrum disorders, I believe a causal relationship in that regard to be tenuous at best, especially in light of the data linking the light from televisions to drops in melatonin production. Since children on the spectrum are often more drawn and attached to screen time than other children, a correlation between ASDs and low melatonin levels is not surprising.
However, girls on the spectrum, due to social immaturity, are often drawn towards or easily duped into intimate relationships at an early age. They can tell that it's a way to gain popularity or manipulate the opposite sex, but lack the skills to engage in or navigate romantic relationships in a safe and healthy manner. They often can also be easily convinced to confuse physical and emotional intimacy. The early onset of puberty, however, compounds these risks by making such girls physically attractive at an earlier age and spurring prematurely the production of hormones that make them wish to seek sexual relationships. In short, early onset of adolescence is especially dangerous for girls with AS.
While I highly doubt that television watching is the primary cause of the rising incidence of early puberty in girls, it is one of many potential causes...a potential cause with an increasing body of evidence behind it, and a potential cause that is not receiving much attention among the general populace. It's also a potential cause that is relatively easy for parents to control (certainly easier than diet or exposure to estrogen mimics, for instance).
In any case, limiting screen time, especially in the evening, can't hurt.