I've had a problem with mental fatigue and fog for a long time, mostly due to fibromyalgia. Treatment for fibro has helped, but I still have the mental fatigue a lot. I started redimind 2 months ago. Nothing for about a week, taking one a day, in the morning. Then one day, about an hour after taking it, the fatigue lifted and I could think clearly. My typing has gotten much better, the fatigue makes it pretty bad, and I used to type for a living. It seems to last 5 or 6 hours. I'm really impressed!