The charity was previously known as Rethink and the appointment follows a rebrand as part of a larger profile-raising strategy.
The rebrand includes a new logo, visual identity and will include a new advertising campaign, featuring the slogan: "Changing attitudes, Changing Lives". The new campaign will use digital media and print to drive awareness of the charity's work.
The charity was founded nearly 40 years ago to "give a voice to people affected by mental illness, their families, carers and friends." It also lobbies for change to policy and practice at both a national and local level.
Mark Davies at Rethink Mental Illness, said: "The7stars has fantastic experience in the charity space, and in the mental health support space, its credentials are fantastic.
"It's important to us that we work with people that understand our mission as a charity, and the importance of awareness and sensitivity around mental health issues. And of course, the7stars’ strategic thinking wowed us throughout the appointment process."
Creative is handled by social marketing consultancy Audience, part of the M&C Saatchi Group. The account moves from Edinburgh-based Feather Brooksbank.
Liam Mullins, head of press at the7stars, said: "Rethink Mental Illness is a hugely important charity – it has been around for more than four decades and doesn't just support people experiencing mental illness and their families, but also lobbies for real change in the issues that matter.
"We have some creative and brilliantly targeted work underway for them and we can't wait to see the results."
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