A 14-year-old British girl died from an act of self-harm while suffering from the "negative effects of online content", a coroner said Friday in a case that shone a spotlight on social media companies.

Molly Russell was "exposed to material that may have influenced her in a negative way and, in addition, what had started as a depression had become a more serious depressive illness," Andrew Walker ruled at North London Coroner's Court.

The teenager "died from an act of self-harm while suffering depression", he said, but added it would not be "safe" to conclude it was suicide.

Some of the content she viewed was "particularly graphic" and "normalized her condition," said Walker.

Russell, from Harrow in northwest London, died in November 2017, leading her family to set up a campaign highlighting the dangers of social media.

"There are too many others similarly affected right now," her father Ian Russell said after the ruling.

"At this point, I just want to say however dark it seems, there is always hope.

"I hope that this will be an important step in bringing about much-needed change," he added.

The week-long hearing became heated when the family's lawyer, Oliver Sanders, took an Instagram executive to task.

A visibly angry Sanders asked Elizabeth Lagone, the head of health and wellbeing at Meta, Instagram's parent company, why the platform allowed children to use it when it was "allowing people to put potentially harmful content on it".

"You are not a parent, you are just a business in America. You have no right to do that. The children who are opening these accounts don't have the capacity to consent to this," he said.

Lagone apologized after being shown footage, viewed by Russell, that "violated our policies".

Of the 16,300 posts Russell saved, shared, or liked on Instagram in the six-month period before her death, 2,100 related to depression, self-harm, or suicide, the inquest heard.

Children's charity NSPCC said the ruling "must be a turning point".

"Tech companies must be held accountable when they don't make children's safety a priority," tweeted the charity.

"This must be a turning point," it added, stressing that any delay to a government bill dealing with online safety "would be inconceivable to parents".