Marcel,
Here is a description of the Blues scale from playpianonow.com: "The Blues Scale is a six-note non-diatonic scale consisting of the root, minor third, fourth, minor fifth, fifth, and minor seventh degrees of the major scale. In the key of C the blues scale consists of the notes C, E flat, F, G flat, G, B flat, and C (again).
If you are taking anti-depression medication because of depression, it's the depression the causes you to be unable to concentrate, not the medication.
Dr. Quack