"While digital devices promise to keep us connected, they frequently do the opposite," Kate, the wife of heir Prince William wrote in a joint essay with Professor Robert Waldinger from Harvard Medical School.
Kate, who has three children - Prince George, 12, Princess Charlotte, 10, and seven-year-old Prince Louis - said the challenge was "particularly acute" for babies and young children born into a world immersed in digital technology.
In an interview with Eugene Levy for the actor's travel show that aired last week, her husband William said none of their children were allowed phones.
"We're raising a generation that may be more 'connected' than any in history while simultaneously being more isolated, more lonely, and less equipped to form the warm, meaningful relationships that research tells us are the foundation of a healthy life," Kate, 43, said in her essay.
She cited findings from Harvard's adult development study, the world's longest-running on the subject, which showed the best predictor of a happy and healthy life was the quality of an individual's connections with other people.
"If you could invest in just one thing to help you and your family thrive, invest in the relationships you have with each other," she said.
"Look the people you care about in the eye and be fully there - because that is where love begins.
"For babies and children who are raised in attentive and loving environments are better able to develop the social and emotional skills that will allow them to grow into adults capable of building loving partnerships, families, communities. This is our children's greatest inheritance."
The essay was published by Kate's Royal Foundation Centre for Early Childhood, which she launched in 2021, before a visit on Thursday to an Oxford charity which supports families with young children.
