"The number of psychiatric referrals has dropped significantly since we started," says the project's co-ordinator, Eve Marie Haydock.
Penumbra runs three school-based groups in the Borders: voluntary peer groups in Secondary 6 at Eyemouth High School and Selkirk High, personal and social education classes for S5 at Eyemouth, and a pioneering Friday lunchtime drop-in session with a counsellor at Eyemouth.
"We want young people to think about mental health issues positively and so far the response has been very good. We begin by looking at stereotypes of mental health and expose common myths, such as only girls get anorexia or once you're suicidal you're suicidal for life," explains Miss Haydock.
"We explore differences between mental health problems and mental illness. You could have a mental health problem because you're being abused, but that doesn't mean you're mentally ill.
"We look at issues which affect young people, such as drugs and alcohol, sex, relationships, getting to university or finding a job, and then look at how best to cope with them.
"It's important to show that it's a series of events which leads to depression and that you don't just suddenly wake up one morning feeling depressed or suicidal.
"The young people identify issues which they want to look at and we get them to research them. Mental health affects us all at some time and our aim is to tackle the social stigma surrounding the issues. Our work is preventative."
Penumbra's work has been a big success at Eyemouth High School, says Mike Ainslie, the principal teacher of guidance. "Last year the S6 peer group put on a drama about teenagers in a real-life situation dealing with hassles at home, in schoo, with jobs and relationships. They performed it for the whole school and taped it. The group's improvement in self-confidence was palpable and the whole project has had a positive effect.
"This year the S5 pupils are looking at mental and emotional health as part of the Higher Still PSE curriculum, examining areas of their own choice covering self-harm, exam pressure and drugs. It's a great way of introducing a subject which has been avoided in the past. It's challenging and it has brought pupils to guidance who have found some of the sessions difficult, but they have always gone back in.
"Our Friday lunchtime drop-in centre is run by a member of Penumbra. I think it is a significant development and its use is growing. Issues raised in the PSE classes sometimes lead pupils there to discuss them.
"My experience is that it is more anxiety than depression that is apparent across schools. We are asking young people to take huge decisions, and fear of failure is a main anxiety. The Penumbra project is a really positive model to develop. It is geared to young people's needs."
Neither Eyemouth nor Selkirk High's involvement in the project was crisis-led. Don Ledingham, depute rector at Selkirk, sees it more as "a recognition that mental health is an issue for young people" and regards low self-esteem as "a major problem".
"The S6 peer group approach is invaluable, because when it comes to issues which directly affect young people's lives, they'll listen more to peers than adults. These pupils, a hard core of 12, stay behind for about two hours a week. They're working on a video at the moment which they'll produce, direct and appear in.
"The students see they're being given the opportunity to have a genuine impact on school life without management interference. That fits with our ethos of pupil independence and building a community," he says.
Penumbra hopes to expand the project in the Borders this year.