John's top 10 causes of eschatological anxiety first appeared in Dear Hank and John episode 29, Barbershop Genghis and went like this:

1. apocalyptic bird flu and/or flu caused by a different animal
2. solar flare
3. nuclear war that dramatically reduces the population of humans
4. disappearance of Earth's magnetic fields
5. weaponized hemorrhagic virus, like Ebola but weaponized
6. volcanic super-eruption
7. unexpected asteroid
8. artificial intelligence run amok, which I call the Terminator scenario
9. nanotechnology run amok, which I call the grey goo scenario
10. my personal death.

In the Vlogbrothers video "The Looking for Alaska movie, Davos, and Hufflepuff Shade: It's Question Tuesday" the list was ammended to the following:

1. My personal death.
2. Apocalyptic bird flu and/or flu caused by a different animal
3. Catastrophic climate change
4. Nuclear war
5. Disappearance of Earth's magnetic fields
6. Weaponized hemorrhagic virus
7. Volcanic super-eruption
8. Solar flare
9. Artificial intelligence run amok
10. Unexpected asteroid