“there may be a trade-off here: extra years of life versus happy years of life” — This is an…
Neil Thin

You are right that better mental health is often correlated with better physical health, but the trade-off I’m talking about is at the policy level: between treatments for the two. It could be that diverting more resources to mental health is actually beneficial for longevity, and so we get a double whammy by doing so and life expectancy rises by even more. But my point that we are looking at an incomplete picture still stands.