Martha Plimpton is "not ashamed" of her ADHD.

The 54-year-old actress received her diagnosis of the condition in her early 50s and has now said getting it was a "huge relief" instead of a worry as it helped explain her behaviour.

Appearing at the premiere of Task in New York City while wearing a necklace that read 'ADHD', she told Page Six: "I'm actually a late diagnosis ADHD, like millions of others.

"It was actually a huge relief to be diagnosed. So many little things fell into place and made sense that hadn't made sense before.

"I'm not ashamed and (I'm) finally free. I'm glad to be sharing my ADHD-ness with the world."

According to the US National Institute of Mental Health, attention-deficit hyperactivity disorder is defined as a developmental condition with symptoms of inattention, hyperactivity and impulsivity.

It is described as "chronic and debilitating" and one that can affect many aspects of daily life.

Martha is returning to television in Task, in which she plays an FBI supervisor alongside Mark Ruffalo, 57. Speaking about her role, she said: "She's a special agent in charge, and she's a woman, so she's worked really hard to get where she is.

"So that means she's had to deal with some bulls***.

"She's a woman who I think knows how to cut through the c*** and take care of business."

Along with being candid about her ADHD, the actress has long been an advocate for abortion rights.

Despite the 2022 overturning of the Roe v Wade ruling, she said she remained determined to continue speaking out about the issue.

She has said: "I never lose hope, that's what they want.

"It's absolutely possible to avail oneself of the tools and mechanisms to self-manage one's own abortion. "I think it's really important to spread the message that mifepristone and misoprostol are still legal in this country, they're still accessible, and they're a perfectly safe and reliable way of terminating a pregnancy."

The US Supreme Court overturned Roe v Wade in June 2022, ending the federal constitutional right to abortion and allowing individual states to set their own laws on the procedure.

Martha's Task series will air on HBO and HBO Max from 7 September.