Can major depressive disorder, generalized anxiety disorder, obsessive compulsive disorder be cured?

All at once or: All at once, or one at a time? Those are 3 major disorders and there are many types of each of them. So the answer is yes, and no. It depends on which disorder and how much of a physiological component there is in each illness. You can not cure diabetes, but you can learn to control it. That is true of many psychological disorders as well.