As the Christie Brinkley-Peter Cook divorce proceedings get ever messier, a court-appointed expert witness, Dr. Stephen Herman, explained Tuesday just why Cook fell into the arms of 18-year-old Diana Bianchi. In his testimony before the court, the good doctor diagnosed Cook with narcissism, saying the affliction had led the poor man to lead a "triple life"—one with Brinkley, one with Bianchi, and one with some pricey Internet porn.

In 2006, Cook was caught having an affair with the then 18-year-old Hamptons high schooler Bianchi, which sort of put a damper (as teen sex often will) on his 10-year-marriage to the woman best known as a former American Sweetheart/Mrs. Billy Joel/your junior-high beat-off material.

Thank God we finally have the medical knowledge to explain such behavior.

In layman's terms, narcissism is a term used to describe any run-of-the-mill, self-obsessed asshole; in psychiatric parlance, it's a serious, oft incurable, personality disorder. This disorder, Herman explained to the court, means Cook "needs constant reassurance that he is a terrific guy; handsome, accomplished.... Where most people need some quiet feeding with their egos, Mr. Cook has an insatiable appetite." And sometimes, it seems, the only way to satisfy such an appetite is with the flesh of a high school student.

Cook's $3,000-a-month penchant for online porn and webcam masturbation are just further symptoms of this debilitating disorder, it seems. "It's not all that unusual for men to view Internet porn," Dr. Herman said, but Cook's use of it falls "outside the bell curve," especially the live webcam masturbating stuff.

Unfortunately, when husbands seek out such nubile balms for their narcissism, their wives don't always understand. Silly women. Through the sort of blinding insight that comes only after years of study and practical experience, Dr. Herman was able to also diagnosis Brinkley. She is angry, "full of fury," in fact. He said that psychotherapy could help her with her anger management.

Sadly, though, couch time might never be enough to cure Cook's narcissism. Until there's a cure ... there's Internet porn.