That's an impossible claim to backup. A traditional unemployment rate may result in a 2.5x increase in mortality rate, but this isn't a normal period of unemployment -- congress just injected an unimaginably large amount of money into the economy with the deliberate goal of keeping the unemployed afloat until things can re-open.
You can't really look at a past study of unemployment effects and expect it to be anything like what we're about to experience; we literally have no idea.
You're correct that we have no idea, but it's likely to be worse. Some communities won't come back from this.
The economy cannot be paused without massive stimulus to keep it afloat (and no, the current stimulus isn't keeping it afloat). Some companies are entering bankruptcy as we speak. They aren't coming back.
You can't really look at a past study of unemployment effects and expect it to be anything like what we're about to experience; we literally have no idea.