It's not immediately obvious that the excess deaths are lockdown related deaths. There's also a growing overdose epidemic among that age group, for example.
It's well supported that the combination of lock down isolation[1] in addition to the free CERB money resulted in the spike of drug abuse / suicide deaths[2].
[1] https://www.aei.org/op-eds/the-coronavirus-is-killing-thousa...
[2] https://www.cbc.ca/news/politics/cerb-pandemic-opioid-addict...
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And I don't believe we have even begun to see the psychological / developmental effects of isolation and distance learning on young kids.