Why did Weiner do it?

His pattern of behavior is intriguing to mental health professionals and experts on sexual behavior, who — while they emphasize they cannot offer an authoritative diagnosis without examining him — discussed a variety of possible explanations for such conduct.

Some suggested the indiscretions might be an addiction with neurological roots. Others theorized that Mr. Weiner, a Democratic candidate for mayor of New York, could be meeting sexual needs unsatisfied in a marriage. And still others said he might be driven by a combination of a mood disorder and feelings of inadequacy to seek reassurance about his masculinity from women he had never met…

“It’s almost as if a little child were playing at being a politician and trying to hide something,” Dr. Friedman said. “The level of denial is so great, and it’s so incompatible with major responsibility, that the psychological puzzle is not only to find out why he’s doing the particular behavior, but why somebody would be functioning at such an uneven level.”…

“There’s a different type of narcissism that’s based on self-esteem problems, in which the person then defensively covers up by saying: ‘Aren’t I wonderful? Look at my wonderful organ. Isn’t it beautiful?’ ” he said.