New research finds that using antidepressants during pregnancy nearly doubles the risk of autism.
The findings stem from a study by Anick Bérard, Ph.D., of the Universite de Montreal, an internationally known expert in the field of pharmaceutical safety during pregnancy.
Berard said the researchers were surprised by how much the autism risk increased.
“Because we have studied antidepressants for such a long time now, we were expecting to find an association — but not such a huge association between the most used class of antidepressants during pregnancy, which is the SSRIs,” she said, referring to selective serotonin reuptake inhibitors.
Bérard came to her conclusions after reviewing data covering 145,456 pregnancies. “The variety of causes of autism remain unclear, but studies have shown that both genetics and environment can play a role,” she explained.
“Our study has established that taking antidepressants during the second or third trimester of pregnancy almost doubles the risk that the child will be diagnosed with autism by age seven, especially if the mother takes selective serotonin reuptake inhibitors, often known by its acronym SSRIs.”
The study findings are published in the peer-reviewed journal JAMA Pediatrics.
Bérard and her colleagues worked with data from the Quebec Pregnancy Cohort and studied 145,456 children between the time of their conception up to age ten.
Researchers reviewed a comprehensive data set that contained detail about the mother’s use of antidepressants and the child’s eventual diagnosis of autism. Important additional details were included in the data enabling the team to tease out the specific impact of the antidepressant drugs.
For example, some people are genetically predisposed to autism (i.e., a family history of it.) Maternal age, and depression are known to be associated with the development of autism, as are certain socioeconomic factors such as being exposed to poverty, and the team was able to take all of these into consideration.
“We defined exposure to antidepressants as the mother having had one or more prescription for antidepressants filled during the second or third trimester of the pregnancy. This period was chosen as the infant’s critical brain development occurs during this time,” Bérard said.
“Amongst all the children in the study, we then identified which children had been diagnosed with a form of autism by looking at hospital records indicating diagnosed childhood autism, atypical autism, Asperger’s syndrome, or a pervasive developmental disorder. Finally, we looked for a statistical association between the two groups, and found a very significant one: an 87 percent increased risk.”
Researchers found a similar result when they only considered children who had been diagnosed by specialists such as psychiatrists and neurologists.
Experts believe the findings are important as six to 10 percent of pregnant women are currently being treated for depression with antidepressants.
In the current study, 1,054 children were diagnosed with autism (0.72 percent of the children in the study), on average at 4.5 years of age.
Notably, the prevalence of autism amongst children has increased from four in 10,000 children in 1966 to 100 in 10,000 today. While that increase can be attributed to both better detection and widening criteria for diagnosis, researchers believe that environmental factors are also playing a part.
“It is biologically plausible that antidepressants are causing autism if used at the time of brain development in the womb, as serotonin is involved in numerous pre- and postnatal developmental processes, including cell division, the migration of neurons, cell differentiation and synaptogenesis — the creation of links between brain cells,” Bérard said.
“Some classes of antidepressants work by inhibiting serotonin (SSRIs and some other antidepressant classes), which will have a negative impact on the ability of the brain to fully develop and adapt in-utero.”
Knowledge of the potential impact of antidepressant medications is an important consideration as the World Health Organization indicates that by the year 2020, depression will be the second leading cause of disability throughout the world, after heart disease. This leads the researchers to believe that antidepressants will likely remain widely prescribed, including during pregnancy.
“Our work contributes to a better understanding of the long-term neurodevelopmental effects of antidepressants on children when they are used during gestation. Uncovering the outcomes of these drugs is a public health priority, given their widespread use,” Bérard said.