In 2016, Shailene Woodley was arrested while protesting against the Dakota Access pipeline at the Standing Rock reservation in North Dakota.

Now, in a candid new interview, the outspoken advocate for environmental issues and Native American rights has recalled her brief experience behind bars – and how her contact with the US penal system affected her mental health.

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The Big Little Lies star – who was detained and charged with criminal trespassing and engaging in a riot – remembers seeing two military tanks at the protest before her arrest.

“This is some Divergent shit,” she says, during an interview with Marie Claire (a nod to the dystopian trilogy film she starred in).

“The only time in my life that I saw a tank like that was on set in Atlanta.”

Approximately 40,000 people watched Woodley’s October arrest via a Facebook Live post (recorded by the actor’s mother). Fans saw police zip-tie Woodley’s hands behind her back, before she was read her rights and taken to Morton County jail.

It was there, says Woodley, that police stripped her and performed invasive searches.

“I was strip-searched. Like get naked, turn over, spread your butt cheeks, bend over,” she recalls.

“They were looking for drugs in my ass. When you’re in a jail cell and they shut that door, you realise no one can save you. If there’s a fire and they decide not to open the door, you’ll die. You are a caged animal.”

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After the arrest, Woodley says she turned off her phone for three months while experiencing what she has said were symptoms of post-traumatic stress disorder.

“There was so much trauma,” she explains.

“Mine was like, ‘What do I do now?’ Kind of like a little bit of depression.”

The Morton County Sheriff's Department responded to Woodley's comment in a statement to ABC News, saying: “As is standard procedure within detention facilities, all arrested individuals must undergo a visual assessment in which they are checked for any open wounds or sores, bruising, cuts or other health risks, as well as the possession of drugs.

“This is to ensure the safety of the other inmates in which they will be housed."

The statement added that “all female inmates are assessed by female law enforcement, and male inmates by male law enforcement.”

Woodley, who is currently working on a new film, Adrift, accepted a plea deal earlier this year in which she pleaded guilty in exchange for one-year probation.

Images: Morton County Sheriff