Farrell's son James, now 20, was diagnosed in 2007 with the rare neurogenetic disorder characterized by developmental delays, lack of speech, seizures and impaired balance.
Colin Farrell is sharing how he's honoring his 20-year-old son, James amid his lifelong battle with Angelman syndrome.
In a rare new interview with People, Farrell got candid about James' condition and his diagnosis.
James, now 20, was diagnosed with Angelman syndrome in 2007 -- a rare neurogenetic disorder characterized by developmental delays, lack of speech, seizures and impaired balance. Angelman Syndrome is often misdiagnosed as autism or cerebral palsy, and that's exactly what happened with James.
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View Story"It was at the time -- it probably still is, but in less measure -- it was a common misdiagnosis, because it shared a lot of the same presentations, a lot of the same characteristics," Farrell told the outlet.
It wasn't until his son was about two-and-a-half that the Academy Award-nominee, who shares James with his ex, model Kim Bordenave, said a pediatric neurologist noticed a telltale sign of the syndrome -- sudden outbreaks of laughter.
"The doctor saw that James was laughing a lot in the office," Farrell recalled. "This pediatric neurologist just took a look at James and said to James' mom, 'Has he been tested for Angelman syndrome?' And Kim said, 'What's that?'"
"Very few people knew about it at the time," he continued. "The doctor said, 'Well, let me just do a genetic test, a blood test. We can just do a genetic mapping,' and it came back positive."
"One of the biggest issues and one of the most significant moments you can experience as a child who has developmental disability or delay is getting a diagnosis, 'cause then if you get a diagnosis you can zero in," Farrell explained.
"There are usually people you can find, whether it's a community just emotionally to lean into, so you feel less alone in your struggles, or medical professionals, and physical therapists, and people who can have a specific system with which they can present to your child, present to you, and then help your child reach their potential."
While the Banshees of Inisherin actor has largely leaned into that support system over the years to aide in James' care, this interview marks the first time he's really opening up about his son's condition and the way he wants the world to see him as he approaches his 21st birthday.
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View Story"I want the world to be kind to James," the actor told outlet.
I want the world to treat him with kindness and respect."
That also happens to be the age where James will age out of many of the support systems provided for families with kids who have special needs.
"Once your child turns 21, they're kind of on their own," Farrell said. "All the safeguards that are put in place, special ed classes, that all goes away, so you're left with a young adult who should be an integrated part of our modern society and more often than not is left behind."
That's part of the reason Farrell decided to launch his foundation -- the Colin Farrell Foundation -- to provide support for adult children who have intellectual disabilities through advocacy, education and innovative programs.
"This is the first time I've spoken about it, and obviously the only reason I'm speaking is I can't ask James if he wants to do this," he maintained of his son, who is nonverbal.
The actor then clarified that he can ask, and does "speak to James as if he's 20 and has perfect fluency with the English language and age-appropriate cognitive ability."
"But I can't discern a particular answer from him as to whether he's comfortable with all this or not," he explained, "so I have to make a call based on knowing James's spirit and what kind of young man he is and the goodness that he has in his heart."
James, Farrell said, "has worked so hard all his life, so hard. Repetition, repetition, balance, his jerky gait. When he started feeding himself for the first time, his face looks like a Jackson Pollock by the end of it."
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View StoryHe continued, getting emotional at multiple points throughout the interview, "But he gets it in, he feeds himself beautifully. I'm proud of him every day, because I just think he's magic."
As for the foundation, Farrell, who is also a dad to younger son Henry, 14, whom he shares with his Ondine co-star Alicja Bachleda-Curús, said it's something he's wanted to start for years.
"[The foundation] is providing greater opportunities for families who have a child with special needs, to receive the support that they deserve, basically the assistance in all areas of life," Farrell explained.
James and those like him have "earned the right to have a greater degree of individuality and autonomy in life, and a greater degree of community," he added.
Farrell is also choosing to believe that James is in support of getting his photograph taken in the garden -- which is not his favorite thing to do. "if us doing this could help families and other young adults who live with special needs, he would say, 'Dad, what are you talking about? Why are you even asking me? It's a no-brainer.'"
"So that's why we're doing it," he added. "This is all because of James -- it's all in his honor."