(Image source: Babble )

BY TRACY PFEIFFER

ANCHOR CHRISTINA HARTMAN

You're watching multisource health video news analysis from Newsy. 

Experts say -- two new studies -- published at the same time -- could change everything doctors thought they knew about what causes autism.

First -- a look at twins.

“Now one of the largest studies of twins with autism and related disorders shifts the focus to the womb itself, suggesting that the mother’s age and her health may play a larger role than previously thought, and while the study doesn’t solve the mystery of what causes autism, it shows that faulty genes and outside factors may be at work.” (NBC)

Researchers used twins -- because of what they can tell us about genetics.

If autism and related disorders were mostly genetic -- identical twins would almost always both have the condition.

Fraternal twins - who should have the same genetic similarities as other types of siblings - would have the same chance of dual diagnoses as the general population - about 5 percent.

But the San Francisco Chronicle reports...

“...researchers found that only about 60 to 70 percent of the identical twins had dual autism diagnoses - lower than expected - and 20 to 30 percent of the fraternal twins had dual diagnoses - much higher than anticipated.”

Basically -- that means something else - most likely environmental - is a major cause of the disorder.

TIME quotes a senior author of the paper as saying...

"The fact that both groups have elevated rates suggests that something is making the two groups of twins similar to each other... Whether it occurs in utero, during childbirth or soon thereafter, we can't differentiate. But it suggests that something environmental is causing the twins to be alike."

And that open-ended conclusion -- leads nicely into the next study, which found children whose mothers took anti-depressants like Prozac or Zoloft -- also called SSRIs -- before or during pregnancy were almost twice as likely to be diagnosed with autism spectrum disorder.

ABC reports what researchers found after reviewing the medical records of 16,000 children and their mothers.

Dr. TIMOTHY JOHNSON: “Two hundred and ninety-eight of the kids had been diagnosed with autism spectrum disorder. The authors found that 6.7 percent of those children’s mothers had taken a class of drugs called SSRI anti-depressants in the year before they had their babies. By contrast, 3.3 percent of mothers with non-ASD children had taken the same drugs.”

A writer for Care2 says - although the new data is definitely cause for re-thinking ASD, it doesn’t mean mom is to blame.

“...the line is very [thin] between pointing out what women did or did not do during pregnancy, and the long-discredited phenomenon of ‘mother blaming’ as a cause for autism. ...We need to keep this in mind as we try to figure out ways to ensure the best health and outcomes possible for mothers and... for children who are autistic, for whatever reasons or causes.”

Medical experts stress the research is preliminary-- adding-- no one should stop taking anti-depressants or other medications without first consulting their doctor.

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Transcript by Newsy.