Christoph Henking and Ben Baumberg Geiger found that while there has been a steep rise in the share of young Britons reporting a mental illness, the share of people who say a mental health problem limits their day-to-day functioning has barely budged.

…when asked if they would consider someone experiencing typical fluctuations in mood (described as broad happiness but occasional moments of worry, frustration or loss of confidence) as having a mental illness, more than half of young Americans say yes, up from just a fifth 15 years ago. Older people’s views show no such change.

Here is more from John Burn-Murdoch at the FT.  I would second his numerous caveats, and you should not consider this at all conclusive.  But the alternative perspective is not conclusive either.