This isnt to let the drugs off the hook, this would be one possible explanation for long term effects, especially when very little is showing up on standard testing.
I think there could be more to look at though if we step outside the realm of hormones, not to say that hormones aren’t being taken for a ride.
Gut Microbiota Can Drive Neuroinflammation in Major Depressive Disorder
The role of dysregulation of the gut-microbiota-brain axis is evident in Major Depressive Disorder from animal and human studies, according to investigators. The authors concluded that “changes in these glial cells influence brain networks involved in memory, learning, emotions, and mood regulation, what could be behind the onset of depressive symptoms or anxiety.”