A couple of long term studies

Ed Yong post Self-control in childhood predicts health and wealth in adulthood describes a long term study by Terrie Moffitt and colloborators.
There are interesting comments and links to other research Don’t!
The secret of self-control,
From an earlier report in Nature News (about a different study, also started in 1972, by Moffitt and others)
Lighter sentence for murderer with 'bad genes':
"A 2002 study led by Terrie Moffitt, a geneticist at the Institute of Psychiatry, King's College, London, had found low levels of MAOA expression to be associated with aggressiveness and criminal conduct of young boys raised in abusive environments1......
One problem is that the effects of the MAOA gene are known to vary between different ethnic groups, Moffit says. A 2006 study in the United States found that former victims of child abuse with high levels of MAOA were less likely to commit violent crimes — but only if they were white. The effect was not evident in non-white children2.

"If the defendant has any African ancestry, this could bring up a question of how well the genotype of that particular gene could relate to his personal behaviour," Moffitt says."
In THE GENOME CHANGES EVERYTHING Matt Ridley describes among other things Terrie Moffit's studies on MAOA.