In a recent study, Dr. Lisa A. Croen and colleagues suggest that their findings reveal preliminary evidence that prenatal exposure to selective serotonin reuptake inhibitors (SSRIs), a type of antidepressant, may increase the risk of autism spectrum disorders (ASD). A significant body of research has shown that ASD is not merely a genetic disorder. Environmental factors appear to play a crucial role in the development of ASD as well. Therefore, more research efforts are needed to identify environmental factors that may be involved in the development of ASD. For this reason, Dr. Croen and colleagues set out to investigate associations between prenatal exposure to antidepressants and ASD.
Participants were identified via the Kaiser Permanente Medical Care Program in Northern California. A total of 298 children with ASD and 1,507 children with typical development were included in the study. Pharmacy records were used to determine maternal antidepressant usage during the year prior to delivery (i.e., the 3 months prior to conception and throughout the gestational period). Antidepressants were classified into three groups: SSRIs, dual-action antidepressants, and tri-cyclic antidepressants.
Dr. Croen and colleagues designed their study to account for a potential confounding variable, that is, an alternate factor that might explain a relationship found between prenatal exposure to antidepressants and ASD. As you know, just because two factors are found to be statistically related does not necessarily mean that one causes the other. Alternative explanations must be identified and ruled out. In this case, an association found between ASD and maternal antidepressant usage may actually be explained by the underlying psychiatric condition that was being treated. To control for underlying conditions, Dr. Croen and colleagues used patient medical records to identify the existence of maternal psychiatric conditions within the sample of participants.
Prenatal exposure to antidepressants was identified in 20 participants with ASD and 50 participants with typical development, 6.7 percent and 3.3 percent respectively. The results showed that risk of ASD doubled in participants who experienced prenatal exposure to SSRIs during the year prior to delivery. Furthermore, findings revealed that risk of ASD tripled in participants who experienced prenatal exposure to SSRIs during the first trimester of pregnancy. These findings remained significant after controlling for maternal history of psychiatric conditions.
Dr. Croen and colleagues’ findings indicate that prenatal exposure to SSRIs may be an environmental risk factor for ASD. However, since SSRIs could only contribute to a small portion of ASD cases, the authors conclude that SSRIs are probably not a major risk factor for ASD. Furthermore, the authors conclude that while there may be some risk involved in the use of SSRIs during pregnancy, such risk must be weighed against the harm of leaving a maternal psychiatric condition untreated.
Croen, L. A., Grether, J. K., Yoshida, C. K., Odouli, R., & Hendrick, V. (in press). Antidepressant use during pregnancy and childhood autism spectrum disorders. Archives of General Psychiatry. doi: 10.1001/archgenpsychiatry.2011.73