Depression and serotonin: It's more complex than old models

Here's why SSRI antidepressants may not work well for everybody:

(T)here are multiple types of serotonin neurons that can be independently regulated.

This fits well with findings from other groups that there are two types of serotonin receptor in the amygdala, a brain region linked to emotion and anxiety: 5-HT2A receptors that inhibit anxiety, and 5-HT2C receptors that promote it.

Together, the findings might mean that while high levels of serotonin in some brain regions like the prefrontal cortex can lead to improved mood, high serotonin in other regions could have negative effects. ...

However, in the short-term some people taking SSRIs report feeling increased anxiety.

This is "almost certainly due to the activation of one of these groups of sero

tonin neurons", says (Christopher Lowry of the University of Boulder in Colorado).