A selective serotonin reuptake inhibitor is a class of drugs used to treat anxiety, clinical depression, and some personality disorders. In many areas of the world, selective serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed drug for depression. They can also be used to treat certain sexual dysfunctions in men. The way in which a selective serotonin reuptake inhibitor affects depression is by changing the level of a neurotransmitter called serotonin in the brain, which can greatly improve a person's overall mood and the way he interacts with the world.
Like most psychotropic drugs, a selective serotonin reuptake inhibitor can only be obtained through a doctor's written prescription. Ideally, treatment for depression will include other types of therapy besides medication, to give the patient the greatest chance for a full recovery. Medication, of course, is still an integral part of it. A selective serotonin reuptake inhibitor treats depression by increasing the measured levels of serotonin in the brain.
Messages are communicated in the brain when they pass between two nerve cells through a synapse. This synapse is a small space between the cells, and neurotransmitters like serotonin are the chemicals that carry the message from one cell to the other. A small amount of the neurotransmitter compounds are lost in this process, and this is normal. The rest go back the cell that they came from; this process is called reuptake. A selective serotonin reuptake inhibitor treats depression by inhibiting the reuptake process, allowing the nerve cell to be stimulated again and again by the serotonin relaying the message.
While this is generally an effective treatment for depression and other disorders, it is not known exactly why it works. While inhibiting the reuptake of neurotransmitters seems to work, it is not reuptake itself that causes depression, otherwise everyone would suffer from it. One way to think of it is this: when our bodies react to an allergen, we often take an antihistamine drug to block these symptoms, but the symptoms are not caused by a lack of antihistamine in our bodies, per se. So it is that a selective serotonin reuptake inhibitor does not by itself solve the root cause of depression, but rather builds a bridge over it.
Even with the benefits provided by SSRIs, there can be some serious side effects. Many people, for example, will not want to take these drugs for an extended period of time, in part because the body develops a resistance to them eventually. Also, in coming off of these drugs, some people experience a set of symptoms known as SSRI discontinuation syndrome. Within days of decreasing one's dosage, flu-like symptoms can sometimes appear, and may be severe. When left untreated, these symptoms will go away in a matter of weeks, but can of course be very distressing in the meantime.