Medical marijuana and adhd?

Does it work better than Ritalin and methelphenidate?
And what strains help?

It depends on your brain chemistry and how your brain interacts with various cannabinoids - purple haze from one batch will be different from purple haze from another batch; even from the same grower. I would suggest a sativa, something like bubblegum or strawberry cough; or a haze strain.. I find that the more pure indicas won't relax my mind very much.

What about bluedream?

Any strain is worth a try, especially in the hunt to improve your life. Blue Dream (Blueberry x Hazes), I think it might be a little too euphoric and body-relaxing; not invigorating enough to the mind to clear it up. Totally worth a shot though.

Here's a cool older RIU thread on ADHD strains:
https://www.rollitup.org/t/adhd-marijuana-strains.164452/