The chilling new documentaryThree Identical Strangerstakes moviegoers on one wild ride.

What starts out as the heartwarming tale of three fun-loving, 19-year-old New Yorkers who learn they’re identical triplets separated at birth takes several crazy turns.

The film veers into disturbing territory when the brothers and their adoptive families learn that the triplets – and other multiples – were split up as part of a secret social experiment.

“I think it’s impossible to overstate the impact that it had on them,” says director Tim Wardle.

Based on Bernard’s advice, the late renowned psychiatrist Dr. Peter Neubauer of the Manhattan Child Development Center (which has since merged with the Jewish Board of Family and Children’s Services) and his team of researchers set out to study the children, visiting each of them, taking copious notes, giving them psychological tests and even filming them doing everything from riding bikes to jumping on their pogo sticks.

Studying the children was “an opportunity,” Natasha Josefowitz, Neubauer’s research assistant, says in the film, who adds that in the late 1950s “this was not something that seemed to be bad.”

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In a statement to PEOPLE, the board says, “We do not endorse the Neubauer study, and we deeply regret that it took place. We recognize the great courage of the individuals who participated in the film, and we are appreciative that this film has created an opportunity for a public discourse about the study.”

What the brothers and their adoptive parents didn’t know is that the researchers watched their identical siblings do the very same things — and that some of the biological parents in the study had suffered from mental illness.

While David Kellman says he believes his mother “may have had minor issues,” he and his biological brothers all suffered from some kind of emotional distress growing up.

“We were all under psychiatric care as teenagers,” says Shafran.

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They believe that’s because of the trauma from being split apart at such a young age.

What Wardle and the brothers learned from a small, heavily redacted portion of the study that was released to them (it is under seal until 2066) underscored their belief.

“One of the most shocking things was that these psychiatrists are sitting around, saying, ‘Oh, it’s really strange, the children all seem to have these problems,’” says Wardle. “The obvious answer is that you’ve ripped them apart from their siblings.”

Having grown up in loving adoptive homes, Kellman and Shafran say they don’t need a study to know that while genetics plays a big role in shaping personality, so does being a loving parent or guardian. “Caring makes all the difference,” says Kellman.

Wardle hopes the film leaves viewers “thinking about the importance of family,” says Wardle. “Is family about being biologically related to someone, or is it about love?” he says. “Are we products of our genes? Do we have free will? What about the ethics of scientific experimentation?”

Adds Kellman: “This story needed to be told.”

Three Identical Strangersis playing in New York and Los Angles before opening wider on July 6.

For more on the triplets and the psychological experiment that changed their lives, pick up a copy of PEOPLE, on newsstands Friday.

source: people.com