There is also a corresponding decline in alcohol consumption.

One angle that hasn't been researched enough is the link to anti-anxiety and anti-depression medication. These has been a significant rise in the prescription of both to young adults: https://www.medicalnewstoday.com/articles/anxiety-prescripti...

And on these medications there are often severe interactions with alcohol and drugs which would be enough to frighten off most people. Some e.g. bupropion even reduce addictive tendencies entirely.