Bruce Willis' daughter Tallulah uses 2004 red carpet video with her father to shed light on autism diagnosis

Bruce Willis' daughter Tallulah has publicly shared her autism diagnosis for the first time.

The 30-year-old actress, who is the youngest daughter of Demi Moore and Bruce Willis, posted a video on Instagram on 15 March from when she was a child attending an event with her father.

In the clip, taken during the LA premiere of The Whole Ten Yards in 2004, Willis was holding his daughter while he answered questions on the red carpet.

As he was being interviewed, she occupied herself by rubbing his shaven head with her hand and playing with his ears.

She captioned the post saying: "Tell me you're autistic without telling me you're autistic," adding a crying-laughing emoji.

Asked in the comments section of the post if she was diagnosed with ASD, or autism spectrum disorder, as a child, she replied, "Actually this is the first time I've ever publicly shared my diagnosis. Found out this summer and it's changed my life."

ASD is a neurological and developmental disorder that affects how people interact with others, communicate, learn, and behave, according to the National Institute for Mental Health.

Tallulah received plenty of support in the comment section and was widely praised for being candid about her diagnosis.

She took the opportunity to reply to several comments on the post, including one from her sister, Scout LaRue Willis, who commented: "She's stimming." Tallulah responded: "Dude the ear curl. I wish we had stronger audio."

Stimming, or self-stimulating behaviour, involves simple, repetitive movements aimed at soothing yourself, according to the National Autistic Society.

It's not the first time Tallulah Willis has been open about her health in recent years.

She has also shared her struggles with an eating disorder, an ADHD and borderline personality disorder diagnosis, and depression.

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Tallulah has also given regular health updates on behalf of her father since he was diagnosed with frontotemporal dementia (FTD) last year.

His family had earlier revealed he was suffering from aphasia, a condition affecting speech and language.

"What's going on with my dad - he has a really aggressive cognitive disease, a form of dementia that's very rare," Tallulah said in November.

She added they were being open about the condition because "it's who we are as a family".