Several risk factors may have made the fictional Nina susceptible to psychosis if she had a genetic vulnerability, said Lamberti.
"Natalie Portman's character was involved in a highly stressful competition, she had conflicted relationships with her mother and with her understudy, and she was the object of sexual advances by her director," he said. "Any one of these issues alone would be stressful, but experiencing all of them at once could be emotionally devastating, particularly for a young woman who is somewhat naïve and sheltered."
Ecstasy, a powerful hallucinogen that Nina and Lily take in one libidinous scene, can also trigger a psychotic event.
Lamberti also suggests that the repeated vomiting and weight loss in the days leading up to her final performance may have caused an electrolyte disturbance that could have contributed to the psychosis.
The film took liberties with a host of anxiety disorders: anorexia, bulimia, cutting and obsessive compulsive disorder (OCD) -- most of which would not all appear together, say psychiatrists.
Nina is meticulous about preparing her slippers, lining up the make-up in the dressing room and washing her hands at each turn. Viewers see hints of anorexia as she stares at a simple pink grapefruit for breakfast and turns away the fatty cake her mother buys to celebrate getting the coveted role.
Nina also makes frequent bulimic trips to the bathroom to throw-up. Her scratching and cutting is hardest to watch - blood oozes from her fingers as she rips off old scabs.
Director Darren Aronofsky has a "wild imagination, according to Jonathan Abramowitz, associate chair of psychology at the University of North Carolina at Chapel Hill, who specializes in obsessive compulsive and anxiety disorders.
"It would be fairly rare to have a psychosis and an eating disorder," he said. "People in psychosis are not in touch with reality. With eating disorders and OCD, they are too in touch with reality."
Psychosis, particularly in schizophrenia, involves negative symptoms, as patients start "slipping away from contact with reality," said Abramowitz. "They don't care about social interactions and what they look like and speech starts to deteriorate. It's the polar opposite with anxiety disorders and OCD."
Those disorders abound in the dance profession, according to ballet psychologist Nadine Kaslow, who continues to perform and teach.
"The world of ballet is intensely competitive," she said. "They over-exercise and eat very little. Anorexia and bulimia are extremely common. It's not as rampant as it was 20 years ago when we saw people get sick and die. But there is still a lot of controversy over how thin you should be."
Cutting is occasionally seen and substance abuse, particularly with drugs that help the dancer lose weight or keep up energy, is widespread.
"It's all about perfection and you can never be perfect," said Kaslow. "But the demand for it is off the charts."
The exploration of bisexuality was also on point in the ballet world, where men are often gay and where women's physiques are more childlike.
"The ballet world gives you such a message to look like a child," she said. "They are pretty flat-chested and they look like kids. The notion of being sexual or being a woman -- it's not uncommon to struggle with that.