From the no shit sherlock school of research. Being poor is exhausting and debilitating. It's amazing the difference even small amounts of money can have on someone's mental health.
So of course, having enough money to be able to put a small amount of it aside is going to make you feel a lot better than being worried that you might not be able to afford food this week.
Poverty costs the UK £78Bn a year. Maybe we should use some of that to lift people out of poverty