On my walks and runs here in Australia this last week or two, I've noticed a lot more people out and about walking, running and cycling - and the local park's been busier. Unfortunately they're all keeping their distance, so the usual social benefit of not sitting in your car or looking at your phone isn't there. Still, overall they are improving their physical health.
About a million people have lost their jobs (including me - I had to shut my business), and another million will follow shortly. Another few million are now working from home. So some people have all day free, and others are now more productive without the distraction of the open plan office, and they don't have the commute. This gives people more spare time.
Some jobs are so destructive to the person's mental health they are better-off lost, so that some people's mental health will improve unemployed, but most will I think be worse off. But those who are now more productive and not commuting will see an improvement in their mental health.
More people working from home will mean emptier offices. As well, large crowded shopping centres will become less attractive, and smaller more local shops more so. This, by the by, is going to hurt the commercial real estate market badly. But local businesses will do better - it'll take time because of the likely depression we're facing, but they'll come back up.
The panic-buying has given people full pantries and fridges, and restaurants and food courts have closed, so that people will be eating more meals cooked from fresh(ish) ingredients at home, improving their physical health.
The sight of empty shelves has led many people to start trying to grow some of their own food. Obviously due to space and skill limitations this will just be a token amount, nonetheless being a bit more aware by experience what's involved in natural processes of growth and decay, and the trouble taken to produce food, may improve people's sense of connection to natural processes and appreciation of what they're eating.
As they say in Yorkshire, "it's an ill wind that blows no good."