Most doctors consider the Copper coil/interuterine device a non-hormonal form of contraception. That's why I chose it 7 years ago after many years of PMDD on oral birth control pills.

However, I just learned that Copper is known as a xenoestrogen: it binds to estrogen and prevents it being expelled. Copper also depletes zinc, B6 and folate (if I am remembering the info correctly) and can cause/impact PMS symptoms.

I stumbled on this information by chance on r/CopperIUD, so I wanted to signpost others to it. There are links to studies in some of the posts in that sub too.

My key takeaway is that biochemistry understands and acknowledges the impact of copper on our endocrine system, but medicine is largely unaware.

Edit: Personally, I can't say for certain if I'm experiencing negative effects of excess copper (it's not all bad, our bodies do need some copper, but we usually get enough from food). That's because my medical history is such a muddle: years ago I quit oral contraception at the same time as long-term SSRIs. I was angry, tearful and anxious on antidepressants/the pill and I'm the same 7 years on, med free with copper coil! So, maybe it's complex trauma, late-diagnosed ADHD, plain ol' sensitivity to hormone fluctuations, I don't know. But I'm going to have the IUD removed asap and see if it helps me now I'm perimenopausal too!