3. Dilated Pupils
Among many other things, an increase in serotonin can result in dilation of the pupils. This is once again due to the many different complex interactions that occur throughout the body and are modulated by hormones. While we might think that taking lots of a hormone that makes us feel good would simply make us feel really good, the truth is that serotonin and any other hormone actually has interactions with a huge number of other body processes.
Dilated pupils are a sign that we are interested in a person or a thing. They increase in size in order to allow more light in, particularly in situations where we feel safe and secure. This is normally caused by an increase in serotonin which causes the tiny muscles around the eye to relax. But when you produce too much serotonin in serotonin syndrome, the result can be that the pupils appear unnaturally large and don’t change shape. Many people experience things also seeming ‘brighter’ as a result.