Great link TBM.
Commenting mostly to follow the thread and I don't have any real hard data, just anecdotes and a crazy level of passion.
I reckon gardening is awesome for a whole heap of reasons, so much so that I am in the long and unnecessarily complicated process of getting a not for profit seeds supply for low income earners off the ground. (Would only be able to be for Aussie folks due to legal stuff, and wont be happening for a while yet. The paperwork is a nightmare and it is starting to get pretty expensive, but I am plodding away at it. Should be up by this time next year.)
I reckon that gardening(and specifically giving folks seeds, who may have never seriously considered it, or "can't afford it".) is good for social reasons, like creating a bond in the community, increasing neighbourhood co-operation, sparking interest in self sustainability, and improving diet, teaching work ethic, providing a sense of achievement and self-pride, keeping folks minds active, and teaching them new ways to think by having to adapt to changes in growing conditions.
And, they may even get a feed out of it which is great for the economy and decreases the pressure on the welfare system.
I am not saying that gardening is the cure 100% for everything(though I reckon long term it really might be).
But, for example, I reckon if you got 1000 racists, or physically or mentally abusive folks, or depressed folks, or mentally ill folks, or just lonely folks, and gave them some seeds and said here you go bro, do what ever you want with them. You might get 10% of those folks, actually plant them. Only 10%, but that's cool.
That's 100 folks.
Out of those 100 folks who plant them maybe 10% successfully stick with it and grow them, learning about patience, having some down time from the stresses of life and having a positive outcome.
That's only 10.
I firmly believe that out of those folks that do feel better about themselves, do feel a sense of pride with their outcomes, do enjoy themselves and take it with them as a coping mechanism for life, you would have to see a lower level of racism and anger, a lower level of frustration and abusive behavior, and a lower sense of isolation and loneliness, or at least more calm hours in the day than destructive hours, in at least 10% of those successful folks.
That is 1 dude, coping mildly better.
Not all folks, and not a 100% fix, but a mild but measurable difference in social and economic dysfunction.
I know that would only be a help to every 1 dysfunctional dude in every 1000, and probably only a minor help, at having a slightly less dysfunctional day.
But to me that seems like a great outcome when you take into account the cost which is bugger all, and the potential for positive flow on effects though out the community which is huge.
Our Australian government throws millions of $ at much more ineffective programs every day of the year, all year round.
Imagine the societal impact of $1m in seeds shared with the public.
Even $1000 would help a couple folks I reckon, and the thing about gardening is it is for life, it is a lifelong skill, that has its own built in "participation award program".
Everyone that participates in gardening gets free food!
Can't say that about programs.
None of them have a physical, tangible, participation reward program, and that is why none of them really work that effectively long term, and they all have huge ongoing costs, and a massive relapse rates upon completion of the programs.
The other thing about gardening, is that it is easy to teach, much easier than trying to teach tolerance, or calmness or sanity, meaning every mild "success story" from gardening is easily relayed and shared to others, along with the physical proof of success(the vegetables) and initial motivation for giving it a go, the free seeds the "success story" grew.
I reckon gardening is bloody AWESOME!!!