BAGHDAD -- Marwa Hussein watched as gunmen stormed into her home and executed her parents. Afterward, her uncle brought her to the Alwiya Orphanage, a high-walled compound nestled in central Baghdad with a concrete yard for a playground. That was more than two years ago, and for 13-year-old Marwa, shy and thin with walnut-colored eyes and long brown hair, the memory of her parents' last moments is always with her.

"They were killed," she said, her voice trailing away as she sat on her narrow bed with pink sheets. Tears started to slide down her face. As social worker Maysoon Tahsin comforted her, other orphans in the room, where 12 girls sleep, watched solemnly.

Iraq's conflict is exacting an immense and largely unnoticed psychological toll on children and youth that will have long-term consequences, said social workers, psychiatrists, teachers and aid workers in interviews across Baghdad and in neighboring Jordan.

"With our limited resources, the societal impact is going to be very bad," said Haider Abdul Muhsin, one of the country's few child psychiatrists. "This generation will become a very violent generation, much worse than during Saddam Hussein's regime."

Since the U.S.-led invasion in 2003, 4 million Iraqis have fled their homes, half of them children, according to the United Nations Children's Fund. Many are being killed inside their sanctuaries -- at playgrounds, on soccer fields and in schools. Criminals are routinely kidnapping children for ransom as lawlessness goes unchecked. Violence has orphaned tens of thousands.

Marwa copes by taking care of her sisters Aliyah, 9, and Sura, 7, Tahsin said. Marwa helps them with their homework and bathes them. On the playground, she keeps careful watch.

"She's trying to substitute for the role of their mother," said Tahsin, who has been a social worker for 15 years. "But even as she tries to fill this gap, she is in deep need for emotional support as well."