I have heard this theory and believe it is legit; I know I make worse decisions when I've had a horrible, long, exhausting day, so it just seems logical that someone who is commuting two hours each way by bus, working irregular hours, not eating the healthiest foods or getting much exercise, etc., would as well.
I also think that what is a "good" and "bad" decision may vary depending on the context. E.g., I read about a re-do of the marshmallow study that evaluated brain waves, and IIRC, the brain waves of the poor kids when choosing to eat the marshmallow were the same as the brain waves of the wealthier kids when choosing to wait for two. IOW, if you live in a world of scarcity, you learn that if you don't eat the marshmallow now, someone else will, and you won't get any, so the logical solution is to eat the one now. Unfortunately, since the ability to delay gratification seems to be highly correlated with long-term success, I suspect those early life lessons just create another obstacle (mindset) these kids need to overcome.