Pharmalot.com - Rats On Antidepressants Showed Signs Of Autism

PHARMALOT.COM  // October 27th, 2011 

http://www.pharmalot.com/2011/10/rats-on-antidepressants-showed-signs-of-autism/

Yet another study suggests the possibility of a link between antidepressant use and autism. This time, rats given Celexa just before and after birth showed what researchers describe as substantial brain abnormalities and behaviors. Celexa is an SSRI, or serotonin selective reuptake inhibitor, a popular class of antidepressants that includes Prozac, Zoloft, Paxil and Lexapro.

The rodents became “excessively fearful when faced with new situations and failed to play normally with other rats, which is the sort of behavior that is reminiscent of what is known as novelty avoidance and social impairments often seen in autism,” according to the National Institutes of Health, which funded the study. The abnormalities, however, were more pronounced in male than female rats, and the researchers note autism affects boys up to four times more often than girls.

This is the second time in recent months that a study has suggested a link between antidepressants and autism. Last July, a study reviewed medical records of more than 1,800 children, including 298 who have autism, and found the risk of having a child with autism spectrum disorder was about twice as high among women who took SSRIs in the year before giving birth. And there was a three-fold risk associated with SSRI treatment during the first trimester. (see here).

In the most recent study, which was published in the Proceedings of the National Academy of Sciences, male and female rat pups were given the drug before and after birth, and their brains and behavior were examined as they grew (you can read it here).

“The male rat pups abnormally froze when they heard unfamiliar tones and resisted exploring their environment” when encountering unfamiliar objects or scents, according to an NIH statement. What’s more, the behaviors continued into adulthood and the little male rats also shunned normal “juvenile play behavior,” which the researchers noted resembled behavior seen in autistic children.

Specifically, the researchers reported that a key brain serotonin circuit showed “dramatic reductions in density of neuronal fibers.” As a result, they found evidence of “stunted development in the circuit coursed through much of the cortex and other regions important for thinking and emotion, such as the hippocampus,” according to the NIH. There was also damage to a protective sheath around axons, which are extensions of neurons, that was three times worse in little male rats than little female rats.

“Our findings underscore the importance of balanced serotonin levels – not too high or low - for proper brain maturation,” says Rick Lin, one of the study authors and a professor of neurobiology and anatomical sciences at the University of Mississippi Medical Center, in the statement.

There are limitations, though to latest findings. Notably, the results should not prompt anyone to assume SSRIs have the same effect on humans as they did on the rodents. “Importantly, our present findings reveal that exposure to SSRIs can alter the course of development of the rodent fetal nervous system, including an impact on neural network function and behavior,” the researchers write. “Whether such actions occur in humans is unknown. Further investigation is certainly warranted, considering that the prescription rate of SSRIs to pregnant females is on the rise, nearly doubling between 1995 and 2004.”

Nonetheless, the appearance of yet another study is likely to fuel fresh debate about SSRIs. As we have noted before, the suggested association pairs two lingering controversies - the various side effects associated with SSRIs with the origins of autism. In recent years, SSRIs have been linked to suicidal thoughts in youngsters and birth defects (see this and this). There has also been a long-standing debate over research linking the MMR vaccine and autism that was called fraudulent, which is part of a larger controversy over vaccine safety, in general, that has not really abated