In my case: pretty bad brain fog (especially when trying to bring the copper down), bad mood, sleep and digestive issues, no energy whatsoever, and depression. It depends on whether you are actively trying to bring it down or not (you could call it detox, but this word has gotten a bad press, so I would rather not use it).
I do suffer from overload and have been tested. It's common to suffer the same symptoms as someone who has a deficiency when trying to bring those levels down.