[electricviolet]

Do you have any specific citations?

This is an area where it's very difficult to show cause and effect (since you can't exactly do a randomized controlled trial) so I would be skeptical about drawing conclusions that lowered relationship quality is caused by having more partners.

[Mizza]

This was linked elsewhere in this thread: https://www.theatlantic.com/health/archive/2018/10/sexual-pa...

Non-causal and uses marital happiness as a proxy for actual happiness though.