I take 200 mg lamictal, to treat the depressive side of bipolar. When it was upped to 300mg, I became very depressed. I think that what you are thinking is possible. I take 300mg seroquel. I get paranoid if I take less, and if I have to take more, I'm knocked out. Was the depression a flat feeling? because with a lot of medications, being on too high a dose can cause that.