A class of drugs called selective serotonin reuptake inhibitors (SSRI's) are commonly used to treat autism in children as young as two. SSRI's are better known as antidepressants by their trade names--Prozac, Zoloft, Celexia, etc. Serotonin is a neural transmitter in the brain involved in a variety of functions and some studies have implicated low serotonin levels in the brains of children with autism. Serotonin is measured peripherally in the blood or urine and no one has proved that peripheral measures of serotonin correspond to serotonin levels in the brain. A recent study concludes that there is not clear evidence that the SSRI's help children with autism. And I believe that when you look at the group statistics that is true. In our clinic many of the children with autism are prescribed SSRI's at some point. In some children I see no improvement. But in others, usually the younger children with poor muscle tone I see significant improvement so I think a trial is warranted.