New research provides the first evidence that depression can be treated by only targeting an individual's style of thinking through repeated mental exercises in an approach called cognitive bias modification.

The study suggests an innovative psychological treatment called 'concreteness training' can reduce depression in just two months and could work as a self-help therapy for depression in primary care.

Led by the University of Exeter and funded by the Medical Research Council, the research shows how this new treatment could help some of the 3.5 million people in the UK living with depression.

People suffering from depression have a tendency towards unhelpful abstract thinking and over-general negative thoughts, such as viewing a single mistake as evidence that they are useless at everything. Concreteness training (CNT) is a novel and unique treatment approach that attempts to directly target this tendency. Repeated practice of CNT exercises can help people to shift their thinking style.

CNT teaches people how to be more specific when reflecting on problems. This can help them to keep difficulties in perspective, improve problem-solving and reduce worry, brooding, and depressed mood. This study provided the first formal test of this treatment for depression in the NHS.

121 individuals who were currently experiencing an episode of depression were recruited from GP practices. They took part in the clinical trial and were randomly allocated into three groups. A third received their usual treatment from their GP, plus CNT, while some were offered relaxation training in addition to their usual treatment and the remainder simply continued their usual treatment. All participants were assessed by the research team after two months and then three and six months later to see what progress they had made.

The CNT involved the participants undertaking a daily exercise in which they focused on a recent event that they had found mildly to moderately upsetting. They did this initially with a therapist and then alone using an audio CD that provided guided instructions. They worked through standardised steps and a series of exercises to focus on the specific details of that event and to identify how they might have influenced the outcome.

CNT significantly reduced symptoms of depression and anxiety, on average reducing symptoms from severe depression to mild depression during the first two months and maintaining this effect over the following three and six months. On average, those individuals who simply continued with their usual treatment remained severely depressed.

Although concreteness training and relaxation training both significantly reduced depression and anxiety, only concreteness training reduced the negative thinking typically found in depression. Moreover, for those participants who practised it enough to ensure it became a habit, CNT reduced symptoms of depression more than relaxation training.

Professor Edward Watkins of the University of Exeter said: "This is the first demonstration that just targeting thinking style can be an effective means of tackling depression. Concreteness training can be delivered with minimal face-to-face contact with a therapist and training could be accessed online, through CDs or through smartphone apps. This has the advantage of making it a relatively cheap form of treatment that could be accessed by large numbers of people. This is a major priority in depression treatment and research, because of the high prevalence and global burden of depression, for which we need widely available cost-effective interventions."

The researchers are now calling for larger effectiveness clinical trials so that the feasibility of CNT as part of the NHS's treatment for depression can be assessed.

Published in the journal Psychological Medicine, this study was carried out by a team from the Mood Disorders Centre, which is a partnership between the NHS and the University of Exeter and the Peninsula College of Medicine and Dentistry, a joint entity of the Universities of Exeter and Plymouth and the NHS in the South West.