2010: not enough evidence, and any available evidence was low quality.
http://www.cochrane.org/CD006507/BEHAV_meditation-therapies-...It seems like it could be useful, so it's a shame either Cochrane haven't repeated their analysis or that other researchers aren't doing good quality research on meditation.
And you can make money off it. You give it a brand and sell DVDs. That brand then gets assessed, and promoted. Other people who come along and rip off the brand are not being recommended.
Current English advice for ADHD is here: https://www.nice.org.uk/guidance/cg72