The Impact of SSRIs on the Developing Brain
These days many depressed women contemplating pregnancy face the dilemma of whether to take antidepressant medications and risk harming the fetus or avoid the pills and suffer other consequences. Now, a growing body of knowledge offers them help with this decision though it still remains a tough call.
The most popular medications for depression, the selective serotonin reuptake inhibitors (SSRIs) such as Prozac, Zoloft, Paxil and others, work by preventing neurons (brain cells) from reabsorbing serotonin, a neurotransmitter involved in mood regulation. Keeping more of it around in the synapses (spaces between the neurons) increases feelings of well-being and decreases activation of other brain chemicals like those in the limbic system involved in sex, aggression and overeating.
Because of the powerful effect SSRIs have on brain functioning, researchers have been concerned about their effect on brain development. A recent study, discussed in Science News (June 5, 2010), revealed that “…children exposed to antidepressants in the womb are more likely to appear sad or withdrawn at age 3 than those whose moms didn’t take the drugs.” In other cited research, “…babies born with SSRIs in their systems had lower birth weights and were more likely to experience respiratory distress.”
Earlier animal studies linked antidepressant use in pregnant mice and rats with anxiety and depression in their offspring. On the positive side, some animals showed “improved decision-making and spatial-learning abilities.” In other animal experiments using SSRIs, additional effects of these antidepressants included “faulty brain organization and abnormalities” and an increased sensitivity to serotonin.
It makes sense that the brain would be affected by artificially altering exposure to serotonin prior to, or during, the development of the system that regulates it, whether through medication or the stress of depression. One theory holds that there is a critical period for the creation of the network of serotonin sites throughout the central nervous system. During this time, if there’s too much serotonin already in the system, fewer sites would be established, and if there’s too little, too many sites would be produced, both outcomes affecting a child’s ability to cope.
Some researchers have explored other variables in interpreting the results of these studies. Might the mother’s depressed mood also impact the baby’s serotonin system? Depressed women have difficulty with self-care. They are less likely to eat properly, exercise and get proper sleep, and are prone to risky behaviors like using drugs and alcohol, all of which can affect serotonin levels in the baby’s brain. In studies that followed mothers and their children’s adjustment for three years, researchers showed that a mother’s current anxiety level played a more important role in their children’s adjustment than her mood during pregnancy whether or not she used SSRIs.
Genetics also plays a part in brain development. The serotonin transporter gene (SLC6A4), implicated as a factor in susceptibility to depression and PTSD, has several variants. Findings in one study showed that children with two short copies of the gene (less efficient serotonin reuptake) whose mothers were depressed during pregnancy tended toward depression and anxiety at age three. Children with two long copies (more efficient reuptake) whose mothers were anxious during pregnancy showed increases in aggression at followup regardless of whether their mothers were on antidepressants.
What’s a depressed mother-to-be to do? Clearly the stress of maternal depression has its own documented negative effect on the baby-to-be. But taking SSRIs has potential for harm as well. Since SSRIs have been shown to be most effective for moderate to severe depression, perhaps milder depression can be treated in nonchemical ways. A woman needs to do her research, speak to her practitioner and consider her own individual circumstances in order to make an informed decision that minimizes the risks.