Anti-depressants have been around for a while. There are a few different kinds, and all of them affect brain function. The most modern set of these drugs are called SSRIs. This stands for Selective Serotonin Reuptake Inhibitors. Although it’s not entirely clear how they work, (in spite of lots of research) they make a substance called serotonin more available in the brain. This substance (used to help transmit messages in the brain) is one of those substances that make us feel more settled and in control of our lives.