Khaled Sharrouf, right, and two boys reported to be his sons, in a photo posted to Sharrouf’s now-closed Twitter account. (Twitter)

A few weeks ago, a burly, bearded 33-year-old Australian, Khaled Sharrouf, posted a photo on Twitter of a boy, age about 7, holding a severed human head in a Syrian town controlled by the Islamic State extremist group.

“That’s my boy!” a caption on the photo said.

The photo of the child, who is likely one of Sharrouf’s sons, was front-page news in Australia and Britain, where it triggered widespread revulsion.

It also highlighted a little-noticed aspect of the conflict in Iraq and Syria: The Islamic State seems to be attracting — scattered among its recruits — violent young men from the West, many suffering from mental disorders, psychologists say.

A steady stream of young Muslim men have left Britain and Australia to fight for the movement, which has declared a caliphate in territory it has seized straddling the Syria-Iraq border.

Australia’s attorney general, George Brandis, estimates that 60 Australians are fighting in the conflict, giving the country one of the largest shares of combatants from outside the Middle East, based on its population. Many, like Sharrouf, lived on the fringes of Muslim society here, a minority population in a predominantly Christian country. Some, like Sharrouf, are deeply disturbed.

In his home town of Sydney, Sharrouf drifted into petty teenage crime accelerated by depression. His mental illnesses were tallied in court records stemming from a terrorism charge he pleaded guilty to five years ago. After he was released from jail in 2009, he was given a state pension because of his psychological condition.

In Syria and Iraq, where Sharrouf appears to be living with his Australian wife and five children, he openly enjoys the notoriety of being one of Australia’s most prominent terrorists. He poses with executed Iraqi soldiers. A warrant has been issued for his arrest, but authorities acknowledge that there is little chance of apprehending him in rebel-held areas.

In one photograph, which appeared on Twitter in early August, he posed for the Islamic State version of a family portrait. Sharrouf and three preteen boys, presumably his sons, stand in front of the black Islamic State flag wearing camouflage and holding weapons. The youngest, who looks to be about 4, grasps a stockless Kalashnikov assault rifle.

The Twitter account, which has since been shut down, included another, more shocking photo. The oldest of the three boys is pictured holding a man’s head by its hair — using both hands to support the weight.

Posing obediently for the camera, he is dressed like a regular suburban child: a blue polo shirt, matching plastic watch and checked trousers. Apart from the severed head, the only sign that he is in a war zone is a green utility belt strung across his right shoulder.

The photo was taken in the Syrian city of Raqqah, the Islamic State’s declared capital, and posted by an account controlled by Sharrouf, according to the Australian, a newspaper, which ran a digitally altered version of the photo on its front page. Intelligence analysts in Australia say that it is genuine.

U.S. Defense Secretary Chuck Hagel was in Sydney to see Australian officials when the photo appeared Aug. 12. “It’s pretty graphic evidence of the real threat that ISIL represents,” he told reporters, using one of two common acronyms for the Islamic State. The other is ISIS.

Fitting the profile

The group’s leadership is regarded by intelligence analysts as organized and astute. But some of its foot soldiers were abject failures in their home countries. Frederic Bemak, a psychology professor at George Mason University and longtime researcher into war victims and participants, said men with psychological problems are learning that actions condemned as abhorrent elsewhere are seen as heroic in the Islamic State.

He said that “99.9 percent of societies would say it is really, really sick for a father to be photographing his son with a severed head and that’s certainly a sign of mental illness. The difficulty is that it becomes treated as positive behavior in ISIS.”

There is no way of knowing how many Islamic State fighters have had mental health issues. But their movement continues a trend seen earlier in the Balkans, Chechnya and Afghanistan: a deadly militancy that inevitably attracts its share of unstable misfits. Sharrouf’s well-documented medical and criminal history provides a rare insight into one type of Westerner who joins the violent Islamist organization.

Born in Australia in 1981 to Lebanese parents, Sharrouf grew up in Western Sydney, a working-class region with a big Muslim population. He was beaten by his father, was kicked out of school for bad behavior and appeared regularly in children’s court.

Around the time he turned 18, Sharrouf started using amphetamines, LSD and ecstasy, according to records from his 2009 court case. He began to hear voices and was diagnosed with depression by a local doctor, his medical records state. Two years later, the diagnosis was upgraded to a depressive anxiety order. Schizophrenia was added a year later.

He worked part time on construction sites and was frequently in trouble with the law. At times he struggled to grasp reality. He told his parents that he was being followed, and he believed people could read his mind and control his thoughts, according to court records.

Questionable health history

In 2005, he was interviewed by a court-appointed psychiatrist, Stephen Allnutt, and described becoming paranoid after starting to use LSD.

Sharrouf thought people were after him, perhaps even members of his own family, Allnutt recorded in his medical notes, which were introduced in court. Sharrouf thought everyone was lying to him, and he had trouble sleeping.

His treatment was haphazard. Sharrouf used antidepressants on and off, including Risperdal, Luvox, Zyprexa and Avanza, according to court records. He sometimes didn’t know what he was taking or why.

Sharrouf told Allnutt that after he realized he had a problem, he began to socialize with other Muslim men and regularly pray at a mosque. “He found that every time he felt paranoid, the thought of God would relax him,” Allnutt wrote in his medical notes.

In 2009, Sharrouf pleaded guilty to participating in a failed 2005 Islamist plot to detonate bombs in Melbourne and Sydney. He told the court he believed at the time that it was his responsibility, as a devout Muslim, to kill infidels.

At Sharrouf’s sentencing hearing, psychiatrist Olav Nielssen testified that Sharrouf’s mental health had improved and that he was unlikely to return to terrorism. (Nielssen didn’t respond to requests for comment.) A judge sentenced Sharrouf to little more than time already served.

Australian authorities regard Sharrouf as dangerous but are more focused on identifying other Islamic State fighters who might try to slip back into Australia.

“At least Sharrouf has self-identified and provided authorities with almost unchallengeable evidence of his criminality,” said Brandis, the attorney general. “He is somebody who is going to be much easier to deal with than someone who has not revealed their identity.”