Amanda Knox may be free from her Italian prison, but the stress and anxiety of her four-year ordeal in the Italian court system (and tabloid media) has certainly taken its toll on her physically.
Several media organizations like ABC News and The Daily Mail have recently noted Amanda's hair shows signs of thinning.
Extreme stress, poor health and physical trauma can cause hair loss - even in a 25 year old. In most cases, the hair loss is only temporary (known as 'telogen effluvium') - and I think that Amanda's hair will probably regain its previous luster once she's had a few months to recover. However, she could speed up the hair recovery process by getting started on the nutritional supplement Viviscal and a regimen of Low Level Laser Therapy.