system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What’s the difference between the various SSRIs?

Why do they have different effects? What do each of them do differently?
gpt
Assuming you have a basic understanding of how SSRIs work (?). All SSRIs have the same mechanism of action. 

- Some SSRIs are more selective than others. That is, some SSRIs target serotonin receptors very specifically while others are a bit (just a bit) less selective. In comparison, less selective SSRIs will bind to NET and DAT, which impact norepinephrine and dopamine availability, respectively. SNRI drugs like Cymbalta are designed to target both serotonin and norepinephrine receptors. 

- There are differences in how SSRIs are metabolized by the body (which has dosing implications for older adults and people with reduced liver and kidney functions), the half-life of the drug in the body, and how the drug may interact with the metabolism of other drugs. 

- There are some differences in the side effects reported for different SSRIs, with some more commonly causing stomach upset, lethargy, and weight loss.