A new study has linked an increase in the risk of autism to antidepressant use during pregnancy:
Children whose mothers take Zoloft, Prozac, or similar antidepressants during pregnancy are twice as likely as other children to have a diagnosis of autism or a related disorder, according to a small new study, the first to examine the relationship between antidepressants and autism risk.
This class of antidepressants, known as selective serotonin reuptake inhibitors (SSRIs), may be especially risky early on in a pregnancy, the study suggests. Children who were exposed to the drugs during the first trimester were nearly four times as likely to develop an autism spectrum disorder (ASD) compared with unexposed children, according to the study, which appears in the Archives of General Psychiatry.
Rises in autism rates have paralleled the increase in antidepressant use. Additionally, abnormalities in serotonin levels and regulation have been associated with autism:
Roughly 12 percent of the mothers whose children had an ASD were diagnosed with depression or another mental disorder. Previous research has reported an increased risk of autism in the offspring of mothers with mental disorders, but the new study did not find such a relationship in mothers who did not also take SSRIs.
Slightly more than 2 percent of all autism cases among children born in the late 1990s could be attributed to SSRI exposure, Croen and her colleagues estimate. That percentage might be higher today, Croen says, because SSRI use during pregnancy has become more common. A large 2005 study found that 6.5 percent of pregnant women were taking the drugs.
Croen and her colleagues thought to investigate a possible SSRI-autism link for two reasons. First, the rise in autism rates over the past several decades...
Second, evidence from previous studies suggests that people with autism have abnormalities in their levels and regulation of serotonin, a brain chemical involved in mood and numerous other biological processes. SSRIs are thought to increase the availability of serotonin in the brain, and since the drugs pass through the placenta, they could conceivably influence the development of a baby's serotonin system.
In animal studies, changes in serotonin levels during pregnancy have been shown to have "downstream effects" on the development of the fetus and offspring, says Oberlander.
Another recent study found that the environment plays a bigger role than genetics in determining autism:
"This seems particularly important as the reports of an increasing incidence of autism would be more difficult to reconcile with an almost purely genetic cause," said Dr. David Beversdorf, an associate professor at the University of Missouri in Columbia. 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.
These environmental stressors seem to have the greatest impact while in utero.
"[They] are having an impact during the time that the brain is undergoing its greatest and fastest growth spurt and evolution and has cells at different levels of maturity and immaturity and, therefore, is potentially more sensitive to certain stressors," said Dr. Max Wiznitzer, associate professor of pediatric neurology at Case Western Reserve University School of Medicine in Cleveland. "That is why, in my opinion, the 'environment' is the womb."
Previously, antidepressants have been linked to heart disease, breast cancer, and suicides, while being found to be largely ineffective at treating depression.
Antidepressants have been found in drinking water in the United States and Britain. At least 271 million pounds of pharmaceuticals have been released into U.S. waters over the last 20 years, effecting no less than 41 million Americans.