Now a tenth-grader, Hector had been experiencing severe depression since he was in seventh grade. Everyone feels down or depressed every now and then, but Hector felt this way most of the time. He had a hard time making friends, he was not interested in his schoolwork, and he spent most of his time hanging out in his room alone. He had even thought about suicide. At first, his parents believed that this was just a phase he was going through, but then they became really concerned. What was happening to their son, who had been generally upbeat and friendly until a few years earlier? At the insistence of his parents and teachers, Hector started seeing a psychiatrist who tried to help him talk about what he was feeling. Based on her meetings with Hector, she decided to prescribe a type of medication known as an antidepressant. This medication increases the amount of a brain neurotransmitter  called serotonin (ser-ah-TO-nin), which is associated with feelings of well-being and control. The medicine, a selective serotonin reuptake inhibitor (SSRI), works by preventing (inhibiting) neurons from reabsorbing (reuptaking) the chemical messenger serotonin once it is released into the brain. As a result, there is more serotonin available, and this sometimes helps alleviate the symptoms of depression. If Hector’s depression were being caused by too little serotonin, the medication likely would help him.