Environmental catastophes. The terminal stupidity of domestic and foreign policy. Nuclear melt-downs -- remember Three Mile Island? Wars, wars, wars. The thermonuclear suicide of the human species. These adults discussed the topics as if they were discussing private matters that no one else around them seemed willing to mention, and I can recall the shift in mood, the hushed voices, that always preceded these frightening conversations.
Decades later, I have become such an adult.