Last week, it was the Green Lantern on the couch. Before that, Batman. And at the Kenwood Therapy Center, psychologist Walter Bera's clients also often talk about Wonder Woman.

They're all superheroes and they all have weaknesses that make helpful metaphors for the challenges we humdrum humans face.

"There's much more acceptance of our heroes talking about their difficulties," said Bera, who sees new hero depictions as more honest and less black-and-white than in decades past. "It's easier to identify with them. They're less godlike or perfect. Virtually everyone has things they're ashamed of or have difficulty with."

In "The Dark Knight," opening today, Batman struggles with the burden of being powerful -- the kind of angst seen recently with other blemished, big-screen superheroes. From the heartless womanizing of Iron Man and childhood trauma of the Hulk, to the disheveled heroism of Hancock and the fiery depths of Hellboy, today's big-screen heroes ward off powerful villains while also battling their own mortal vulnerabilities.

"The complex characters have become much more common sources of helping make sense of your own life," Bera said. "It's a healthy thing to be more honest and it provides a more complete accounting of the different themes in a person's life."

And so viewers watch with rapt attention as a simple Achilles' heel -- Kryptonite, in Superman's case -- morphs into more believable themes of how our heroes wrestle with hidden identity, political strife and personal ethics.

"It has become a very real part of these stories, where these characters have to overcome not just that obstacle that is thrown in front of them by the bad guy, but overcome the obstacles within," said Dan Jurgens, an Edina writer/artist with DC Comics who worked on "Superman" for about a decade.

"A hero who has to overcome personal character flaws tends to be more interesting than one who does not."

Dark streaks and character changes have always marked a character like Batman, even before the comic books transitioned to film, but keen readers trace a real change to 1986. In that year, the release of "The Dark Knight" and "Watchmen" (set for a film release spring 2009) upped the ante for darker superheroes.

"Batman was actually kind of close to cancellation in the '80s," said James Kakalios, professor of physics at the University of Minnesota and author of "The Physics of Superheroes."

But "The Dark Knight" by Frank Miller revived the character, who came out of retirement with a mean streak, Kakalios said. Kakalios is serving as "science consultant" for "Watchmen," which will push dark themes further than recent screen efforts as an R-rated superhero movie.

Jurgens said realistic heroes and sobering themes reflect current events but still allow for escapism to take our minds off our daily ills. And when screenwriters look at a character's multi-decade comic career, they try to choose the most interesting period.

"We certainly have an audience now that can sustain that complexity," Jurgens said. "There was a time in comic history when everything was explained, almost to a fault."

But the storytelling on film is likely to grow in complexity with the "humanizing of heroes," said Nick Post, owner of the Source comic shop in Falcon Heights.

"The so-called Achilles' heel is always evolving, and it's becoming more nuanced and complicated," Post said.

Which makes for more relatable and believable heroes who continue to seep into the mainstream, and even into Bera's therapy sessions.

"Superheroes," he said, "are the new mythology."

Tony Gonzalez • 612-673-7415