Dozens of US states are suing Meta and its Instagram platform, saying they've fuelled a youth mental health crisis.

33 states have filed a lawsuit in federal court in California, claiming Meta has repeatedly misled the public about its platforms' danger.

Meta says it's disappointed by the lawsuit.

Auckland University health researcher, Samantha Marsh, says there's strong evidence to support the claims.

"Social media in particular has a really negative impact on youth mental health- so that's things like depression and anxiety."

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