What causes Serotonin Syndrome?

Serotonin syndrome is caused by an excess of serotonin in the central nervous system. This condition can occur when there is an increase in serotonin levels due to the use of certain medications, particularly those that enhance serotonergic activity, such as selective serotonin reuptake inhibitors (SSRIs), monoamine oxidase inhibitors (MAOIs), and certain recreational drugs. When serotonin accumulates excessively, it leads to a range of symptoms including agitation, confusion, rapid heart rate, excessive sweating, and in severe cases, can lead to seizures or even death.

The other options focus on low serotonin levels or specific drug interactions. Low serotonin levels would lead to symptoms of depression and anxiety, not serotonin syndrome. The combination of different MAOIs could potentially lead to severe interactions, but it is the excess serotonin that primarily causes the syndrome. Sudden withdrawal from SSRIs may cause withdrawal symptoms or a relapse of depression but does not typically cause serotonin syndrome; rather, it can lead to serotonin rebound, which is different. Thus, the correct answer highlights the fundamental cause of serotonin syndrome as an excess of serotonin in the brain.