The team looked into the effectiveness of holding Cognitive Behavioural Therapy (CBT) sessions for adolescents in secondary schools with the aim of identifying those at high risk of depression, negative thinking and anxiety.

The Government is attempting to prevent children and adolescents developing depression by introducing various programmes in secondary schools to teach skills for well- being. Schools provide a convenient and accessible location for delivering depression prevention programmes.

The researcher’s trial followed the Resourceful Adolescent Programme, a universal depression prevention programme that has been shown to be effective in Australia and New Zealand.

It was delivered to young people between the ages of 12 and 16 at eight schools by trained and supervised graduates and consisted of nine modules and two booster sessions each lasting about 50 to 60 minutes.

The programme aims to develop skills such as emotion-regulation capacities, coping mechanisms and thinking styles, which are reported to protect against the development of depression.

But the Bath researchers found that schools were not the appropriate setting to the deliver the therapy and suggested that more research is undertaken before the initiative is rolled out as part of the National Curriculum.

Professor Paul Stallard who led the study said: "Our findings suggest a more cautious approach is required to the implementation of depression prevention programme in secondary schools.

"Although secondary schools provide a convenient focus for mental health interventions the suitability of this setting for depression focused interventions cannot be assumed.

"We know that therapies such as CBT are effective but it seems they do not work as well in this type of setting. This may be because schools are ultimately designed for academic learning and are not set up to teach psychological wellbeing."

Depression in adolescents is an important mental health disorder. By the age of 19 up to 20 per cent of adolescents will have experienced at least one clinically important depressive episode, which can affect development issues, interfere with education and increase the risk of suicide as well as major depressive disorder in adulthood.

Although depressive episodes may be persistent in adolescents, depression is poorly recognised and comparatively few people receive specialist treatment.

Initial recovery with or without treatment is often good, but recurrence is common, with up to 75 per cent of people experiencing another episode within five years.

The results of the study are published in the paper: Classroom based cognitive behavioural therapy in reducing symptom of depression in high risk adolescents in the British Medical Journal.