If you read the article, what does it mean “better mental health”? It means nothing, the “researchers” just came up with some made up metric that justifies their -probable- initial intended outcome according to their political ideology.
I couldn’t care less of the “mood” of people receiving my taxpayer money to stay home without finding a job. If I’m forced (by threat of violence from the state, mind you) to work more hours to give my money to these people, the minimum I expect, is for the metrics to show that my money, served to speed up these people finding a new job and stop living on my money.
All other metrics are irrelevant.