I was surprised to run into performance issues with this game, occasional frame rate drops. I'm running an FX-6300, AMD R9 270, and 8GB RAM. All settings turned on except ambient occlusion.

Is there a setting I can turn off to improve performance?

It seems everyone who does have an amd card get those performance issues.
So, waiting for a patch or driver update is the only option right now.

I have the same problem. Geforce 960 4GB, latest drivers, Win10 16 GB RAM. In fullscreen and windowed modes.

Same issue only seems to happen when you blow a head or limb off and it stays in view, as soon as you turn away its fine.

I also have an AMD card and today when playing the Hive of the Mantids, I regularly got single digit framerates in the "nest" segments, where mites, drones and the big ones are.