Why do antidepressant meds cause constipation

Question

In other words, how exactly do they contribute to constipation

Answer 1

Antidepressant drugs work by regulating the Autonomic Nervous System.

The autonomic nervous system is divided in the the Sympathetic ("fight or flight") impulses and the Parasympathetic ("feed or breed").

In other words, emotions of depression and anxiety are within the sympathetic.

Feelings of hunger, going to the bathroom and sexual urges are parasympathetic impulses.

For some reason, medication that works on one part of the sympathetic nervous system may have an unintended effect on the parasympathetic.

For example, an antidepressant may have side effects of dry mouth, constipation or changes in sexual function.

I used to take an old style antidepressant called Desipramine. The side effects were extreme dry mouth and constipation. Later on, I took Paxil and it caused me to have delayed ejaculation.

That's probably an oversimplification, but it's one way of looking at it that makes sense, I think.