Hi Amy3boys. I have been taking just 100 mg of Lamictal for about 7 years now. No brain fog that I'm aware of. I don't think I've ever had any brain fog on this dose, but it's possible you just need to adjust to the new dose. I did experience some cognitive dulling at doses of 200 and 300 mg further back in the past. If the brain fog does have anything to do with depression, maybe with a little time that will ease, too. All the best!