I found this really interesting. You all may too!
after I went on an SSRI ‚Äì Zoloft ‚Äì my horizontal nail ridges disappeared, and my nails got really smooth. When I was - I guess - low in serotonin and having all sorts of mood cycling, which is also related to my hormonal ( just to run, menstrual cycle) issues, my nail ridges got pretty bad. Zoloft also helped to regulate my period, so I suspect it somehow helps my brain produce more progesterone