A mental health helpline funded by the Duke and Duchess of Cambridge has become embroiled in controversy after it exposed millions of private conversations.

The UK’s only 24/7 mental health messaging support line, Shout, was revealed to have given access to “entire conversations” from people as young as 13 to third-party researchers, raising ethical and privacy concerns.

The British helpline, funded with a $5.7 million investment from Prince William and Kate Middleton’s Royal Foundation, has been found to have exposed more than 10.8 million messages from 271,445 private conversations between February 2018 and April 2020 for study purposes.

The concerns follow a US investigation that revealed a data-sharing partnership between an American mental health charity text line and a for-profit company.

Shout’s data provided to an Imperial College London research project included “full conversations” about people’s problems.

The study says conversations provided by Shout were of varying length and contained raw textual information of people seeking help.

According to Shout and researchers, personally identifiable information including names, phone numbers and addresses were anonymous, researchers were “trained in security and ethical considerations”, and conversations were only readable on a secure server.

Kate Middleton visits Shout headquarters in January. Photo: Getty

“Outliers”, including extremely short or long conversations ranging from texters who did not engage to those who were considered high-risk scenarios were not part of the study, according to researchers.

However, the approval to share user data goes against previous statements by the charity, which said: “individual conversations cannot and will not ever be shared”.

As reported by The Guardian, a March 2020 version of Shout’s frequently asked question section on its website answered privacy concerns with this promise.

But by late 2021, the FAQ section was updated and the promise on individual conversations had been removed.

In December, the Imperial College London study was published. The study received ethical approval from Imperial College London.

Shout currently responds to questions about storing personal details by saying it “analyses anonymised data from conversations to improve the service and to better understand the mental health of texters”.

“We sometimes share some of this anonymised data with carefully selected and screened academic partners for research purposes,” it states.

The UK’s data protection watchdog, the Information Commissioner’s Office, is reportedly assessing whether Shout and its parent company Mental Health Innovations mishandled user data.

Shout, rebranded from Heads Together in 2019, is a volunteer-driven campaign led by the Duke and Duchess of Cambridge which aims to provide immediate support to UK residents who need it.

The Duchess of Cambridge visited the support service in January for a live demonstration of how the platform worked.