Seems like the study is largely inconclusive because creativity is difficult to measure.

I will say from my personal experience that I am far more creative when I am unmedicated versus when I am medicated. I've come up with great patentable ideas while unmedicated, but I am incapable of actually drafting up the patent applications unless I take my meds.

For me, taking ADHD meds is analogous to decreasing the RAM in my brain. I juggle fewer ideas and am able to concentrate on just one thing and actually produce something.