I've never read The Death of Grass, by John Christopher, which has just been re-issued. At the Guardian Book Blog, Sam Jordison, who did read it as a child, re-visits it, and finds it much, much scarier now that he's a grown up.
"As a boy, I read it primarily as an unusually dark, but highly unlikely imaginary game. Safe in my schoolroom, knowing that the cold war was winding down and blissfully unaware of the approaching recession of the early 1990s, Christopher's threats about A-bombs and food shortages seemed remote, even quaint. Now I have a family of my own and the cold winds of financial meltdown are beginning to bite, the desperation in The Death of Grass seems far closer."
I tended to avoid things that were disturbing as a child, but now, as an adult reading the slew of distopian, cataclysmically awful (plot, not writing) books that are so easy to find in the YA section, it's pretty easy to be anxious about the future.