It's clear exercise has health benefits both physical and mental -- but what if we could actually prove it was more important to your mental health than your economic status?

According to a study carried out by researchers at Yale and Oxford, we may have done just that.

In the study, published in The Lancet, scientists collected data about the physical behavior and mental mood of over 1.2 million Americans.

Participants were asked to answer the following question: "How many times have you felt mentally unwell in the past 30 days, for example, due to stress, depression, or emotional problems?"

The participants were also asked about their income and physical activities. They were able to choose from 75 types of physical activity -- from lawn-mowing, childcare, and housework to weight lifting, cycling and running.

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