Having not watched the video before reading his post, my "what the fuck" was due to thinking that was a quote from the video

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I would say between the age 10-19 the vast majority of people who commit suicide do not own the firearm they use, and it belongs to a parent/guardian.
For other age groups, I think waiting periods as well as suicide prevention material in gun shops and some training for gun shop employees would do a lot more toward preventing suicides then smart guns.
From
https://fivethirtyeight.com/features/gun-deaths/:
Under age 15, cause = suicide: 139 deaths.
Age 15-34, cause = suicide: 5,061 deaths.
I don't see anything for the 10-19 age group, so it's not real clear how many of those 5,061 are from the <19 category. But here's another way to break it down - the legal age to purchase a long gun is 18. Furthermore, I would wager that most homes with firearm + child aged 10-19 have trained the child in handling the firearm in case of an emergency, and that even with biometrics, at some point prior to 19 would have added the child to the "authorized" list of users anyway.
[youtube]XMg0FQS6Fqo[/youtube]
edit - to address a couple other things you bring up ([1]waiting periods, [2]suicide prevention material, [3]training for gun shop employees):
1. IF it's your first firearm, and you're not purchasing it as an urgent need for self defense due to a restraining order or something, I could maybe see waiting periods having an effect. However, while the actual act may come soon after a purchase, the path to being suicidal is not sudden nor impulsive. So I'm not sure how much effect a waiting period would actually have on suicide rates. It's a bandaid solution, reactive rather than preventative.
2. Sure, why not. Easy enough to do, might save a couple lives here and there, non-intrusive, etc. I'm ok with that.
3. Shouldn't be too hard to implement, but I'd be cautious on mandating it or how much leeway there'd be. I'd really rather not have a bunch of pseudo-counselors trying to analyze everyone.