From USA Today:
As many as one out of four veterans of Afghanistan and Iraq treated at Veterans Affairs hospitals in the past 16 months were diagnosed with mental disorders, a number that has been steadily rising, according to a report in today's New England Journal of Medicine.
Records show that 20% of eligible ex-soldiers came to VA hospitals seeking medical treatment between October 2003 and February 2005. Overall, 26% of them were diagnosed with mental disorders, say Han Kang and Kenneth Hyams of the VA.
Post-traumatic stress disorder (PTSD) was most common, diagnosed in 10% of patients, followed by drug or alcohol abuse (9%). Seven percent were diagnosed with depression; 6% had anxiety disorders, such as phobias and panic. Many ex-soldiers had multiple disorders, Kang says.
For more on how the military is handling this problem (patchily and with somewhat understandable ambivalence) see this recent report by PBS's Frontline.