The creator of “One Tree Hill” has been accused of sexual harassment by numerous cast members and crew — who claim to have been “manipulated psychologically and emotionally” by him, to the point where some even needed to seek treatment for post-traumatic stress.

Former showrunner Mark Schwahn allegedly engaged in the inappropriate behavior while on the set of the teen drama series, which aired on the WB from 2003 to 2006 and then the CW from 2006 to 2012.

One of the show’s writers, Audrey Wauchope, took to Twitter over the weekend to detail his alleged actions, without actually mentioning him by name.

“He’s a man in a position of power who was allowed to run a television show for years where this behavior continuously went on,” she tweeted. “Sometimes we wouldn’t luck out and he’d just squeeze his disgusting body in between us and put his arms around us, grinning. He pet hair. He massaged shoulders. I know he did more but not to me so they’re not my stories to share.”

On Monday, 18 women who worked on “One Tree Hill” with Wauchope — including stars Sophia Bush, Hilarie Burton and Bethany Joy Lenz — came forward and joined her in accusing Schwahn of sexual misconduct.

They claimed in a letter, which was sent to Variety, that some of the stuff the 51-year-old did was so bad, people were forced to seek treatment for PTSD, as a result.

“Many of us were, to varying degrees, manipulated psychologically and emotionally,” the letter said. “More than one of us is still in treatment for post-traumatic stress. Many of us were put in uncomfortable positions and had to swiftly learn to fight back, sometimes physically, because it was made clear to us that the supervisors in the room were not the protectors they were supposed to be. Many of us were spoken to in ways that ran the spectrum from deeply upsetting, to traumatizing, to downright illegal. And a few of us were put in positions where we felt physically unsafe. More than one woman on our show had her career trajectory threatened.”

On Twitter, Wauchope described how she first learned about Schwahn’s sexually deviant ways upon arriving in the “One Tree Hill” writers room.

“When I was 29 my writing partner @RachelSpecter and I were hired as staff writers,” she explained. “To say we were excited was an understatement. To say we left that job demoralized and confused is also an understatement. One of the 1st things we were told was that the show runner hired female writers on the basis of their looks. That’s why you’re here — he wants to f–k you.”

Wauchope continued, “Rachel had been actress previous to writing and was told that he used to talk about her in the room before we were hired. So that’s a safe room to enter as staff writers. Imagine what that does to ones psyche. Imagine feeling for the rest of your career that you’re possibly an imposter – that maybe just maybe you’re only here because you’re a body, not a mind. It creeps into your thoughts and keeps you up at night and makes you wonder.”

The former writer, who now works on “Crazy Ex-Girlfriend,” recalled how Schwahn would regularly flaunt naked pictures of a women he was sleeping with while on set.

“Men on staff were shown naked photos of on an actress he was having an affair with,” Wauchope tweeted. “Naked photos she didn’t know were being passed around. Naked photos they didn’t want to see. This is such a violation, both to the actress and to the men forced to look and participate.”

According to cast and crew, Schwahn was ordered to attend sexual harassment training by studio lawyers — but he never actually went.

“I’m furious and sad and everything else for the women who have sat on that couch next to that man,” Wauchope said. “And I’m furious and sad and everything else that years later I don’t feel safe to be able to do anything real about this and that it seems to be happening all over this town.”

In addition to being the creator of “One Tree Hill,” Schwahn also served as a screenwriter, director and producer of the series — which revolved around the lives of young men and women in North Carolina.

He is currently working on the E! network show, “The Royals.”

“We are monitoring the information carefully,” Universal Cable Productions, Lionsgate Television and E! said in response to the Schwahn allegations.

“E!, Universal Cable Productions and Lionsgate Television are committed to providing a safe working environment in which everyone is treated respectfully and professionally.”

Schwahn is just the latest in a long list of Hollywood heavyweights who have been hit with sexual harassment allegations in recent weeks.

Big name filmmakers such as Harvey Weinstein and Brett Ratner have been publicly named by their alleged victims, along with a number of movie stars — including Kevin Spacey and Richard Dreyfuss. TV showrunners and even a DC Comics editor have also been accused.

“There are trickle down psychological effects to all this bulls–t and the town is littered with the collateral damage of abusers who have been given free reign,” Wauchope said. “If you’re sitting on one of these staffs please know whatever you are feeling is real.”

Variety posted the letter that Schwahn’s accusers sent them in full on its website Monday night. It was signed by Danneel Harris, Michaela McManus, Kate Voegele, Daphne Zuniga, India DeBeaufort, Bevin Prince, Jana Kramer, Shantel Van Santen, Allison Munn and members of the crew, in addition to Wauchope, Specter, Bush, Burton, and Joy Lenz.

“All of the female cast members of One Tree Hill have chosen this forum to stand together in support of Audrey Wauchope and one another,” the letter said. “To use terminology that has become familiar as the systemic reality of sexual harassment and assault has come more and more to light, Mark Schwahn’s behavior over the duration of the filming of One Tree Hill was something of an ‘open secret.'”

“The through line in all of this was, and still is, our unwavering support of and faith in one another,” the letter added. “We confided in each other. We set up safe spaces to talk about his behavior and how to handle it. To warn new women who joined our ranks. We understood that a lot of it was orchestrated in ways that kept it out of sight for the studio back home. We also understood that no one was fully unaware. The lack of action that has been routine, the turning of the other cheek, is intolerable. We collectively want to echo the calls of women everywhere that vehemently demand change, in all industries. Many of us were told, during filming, that coming forward to talk about this culture would result in our show being canceled and hundreds of lovely, qualified, hard-working, and talented people losing their jobs. This is not an appropriate amount of pressure to put on young girls. Many of us since have stayed silent publicly but had very open channels of communication in our friend group and in our industry, because we want Tree Hill to remain the place “where everything’s better and everything’s safe” for our fans; some of whom have said that the show quite literally saved their lives. But the reality is, no space is safe when it has an underlying and infectious cancer. We have worked at taking our power back, making the conventions our own, and relishing in the good memories. But there is more work to be done. We are all deeply grateful for Audrey’s courage. For one another. And for every male cast mate and crew member who has reached out to our group of women to offer their support these last few days. They echo the greater rallying cry that must lead us to change: Believe Women. We are all in this together.”