Pondering the potential scarring of children

There was recently a post on Child_Lit (can you tell that I'm catching up on my reading today?) that brought up a point that I, for one, have always wondered. A person on the site wondered if children's would be permanently scarred for life by authors like Edward Gorey. The debate, as far as I have read it, has remained civil but one person thought to drop this particular note:

When people mention this permanent scarring (as they frequently do, and not only in relation to Gorey), do they ever provide any evidence, I wonder? That there is an association between reading certain books and long-term mental damage is a frequently-heard empirical claim that ought, in theory, to be as susceptible to proof or disproof as the association - causal link, yet! - between smoking and lung cancer. Has anyone ever succeeded, or even tried, to prove it with any degree of rigour - or does it remain in the unscholarly realm of the gut reaction?

It seems to me that this question lies at the root of the censorship debate. If children aren't just disturbed by something they read but BRANDED FOR LIFE BY THE HORROR OF A WORK OF LITERATURE then where's the evidence? Have any of you memories of reading something disturbing as a child and, aside from the odd nightmare, think your lives could have been so much better if you had never dared to pick up that dreadful book? Honestly, I wonder.