I've taken both as mood stabilisers at the same time. I'm just on lithium now and it's very effective. I gained a lot of weight on seroquel and it was/is hard to shift
. For me, seroquel helped with my depressive states and lithium with mania but the seroquel wasn't enough for the depression so I take a small dose of it now with lamictal and lithium. I prefer lithium. My mom takes seroquel too and she's gained a moderate amount of weight since starting it.