New Studies Downplay Genetic Causes of Autism: Antidepressant Medications and Other Environmental Factors May Play Greater Roles

It has long been postulated that autism and related disorders are predominantly caused by genetic factors. However, over the past 30 years, the number of children with autism has increased from about 4 in 10,000 to about 40 in 10,000, causing researchers to question whether parental genetic makeup can explain most or all new cases. Now, important new data suggests that environmental factors, including drug exposure before or during pregnancy, may account for the majority of so-called “autism spectrum” disorders.

Two new studies reported in the Archives of General Psychiatry this week stress the importance of non-genetic causes of autism. In the first, Stanford University researchers conducted a large study of twins and found that in the group of study subjects who had been diagnosed with autism-related disorders, those conditions could not be explained by genetic factors in 58% (a majority) of the cases, leading the authors to conclude that non-genetic causes “may have been seriously underestimated in previous studies and the influence of genetic factors on the susceptibility to develop autism, overestimated.” Hallmayer, J., et. al., “Genetic Heritability and Shared Environmental Factors among Twin Pairs with Autism,” Arch Gen Psychiatry, published online July 4, 2011.

Among the non-genetic influences suggested as possible environmental causes of autism-related disorders postulated by the Stanford team include parental age, low birth weight, multiple births, and maternal infections during pregnancy, and other pre and post-natal conditions.

In the second study, researchers from UCLA, Kaiser Permanente, and the Environmental Health Investigations Branch of the California Department of Public Health, found that the risk of having a child with autism spectrum disorder was about twice as high among women who took antidepressant medications belonging to a class of drugs known as Selective Serotonin Reuptake Inhibitors or “SSRIs” in the year before delivery. According to the new data, the autism risk was four times higher in women who took SSRIs during their first trimester of pregnancy. SSRIs include such well-known brands as Prozac, Zoloft, Paxil and Celexa.

SSRI drugs have previously been suspected of causing a number of birth defects, including an increased risk of cardiovascular anomalies, brain and skeletal defects such as anencephaly, craniosynostosis, and omphalocele, as well as limb reduction defects. In another recent study, researchers in Finland found that Prozac (fluoxetine ) use was associated with an increased risk of isolated ventricular septal defects (one or more holes in the wall that separates the right and left ventricles of the heart). In addition, Paxil (paroxetine) was associated with right ventricular outflow tract defects, another serious congenital heart problem. Malm, H., et. al., “Selective Serotonin Reuptake Inhibitors and Risk for Major Congenital Anomalies,” Obstetrics & Gynecology: July 2011 – Volume 118 – Issue 1 – pp 111-120.

Whether or not SSRI medications may increase the risk of autism-spectrum disorders or other serious disorders is of critical importance to mothers and prescribing doctors who must weigh the risks and benefits of various treatments for depression, which is itself a significant and potentially life-threatening condition. The authors of the California study on SSRI use noted that while the increased risk of autism they observed was “modest,” nevertheless “the potential risk associated with exposure must be balanced with the risk to the mother or fetus of untreated mental health disorders.”

It has been estimated that approximately 10% of pregnant women experience depression, and up to 20% exhibit symptoms of depression. Increasing numbers of women have been prescribed newer classes of antidepressants, including SSRIs, and reported data shows up to 3%–6% of pregnant women are using these drugs.

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Again, if you or a loved one has given birth to a child with a birth defect that you feel may be the result of taking an antidepressant during pregnancy, you should contact our lawyers immediately by clicking the link below or calling toll free 1-(949) 557-5800. You may be entitled to compensation for your injuries and we can help.