Impact of Behavioral Activation on Depression and Quality of Life in Patients with Colon Cancer

Colon cancer is common. At diagnosis, about 20% have metastatic disease. The prognosis is determined by the stage of the tumour and the degree of spread, but also by the patient's physical health and other diseases. However, it is not known how the patient's mental health are affected and how common anxiety and depression symptoms are at diagnosis. Depression is known to be one of the most common causes of ill health in the world. It also has been shown that patients with depression and cancer also have a poorer survival rate compared to cancer patients without depression However, previous studies have shown that so-called brief Behavioural activation as therapy for these symptoms has a positive impact on the patient's well-being, but it has not been studied whether it also has a positive impact on the patient's mental health in cancer, and whether it can have a prognostically beneficial effect. The goal of this randomized study is to increase knowledge about, to detect and treat anxiety and depression symptoms in patients with colon cancer, with so-called brief behavioural activation, which can lead to improved care, and possibly improve the patients' prognosis in the form of reduced risk of cancer recurrence and improved survival. All participants will continue their care as usual (CAU), and half of the participants will be randomized to receive a five-session telephone-based BA-treatment spread over two months as an add-on to CAU. All participants will answer a questionnaire in the beginning of the study, 4 weeks after diagnosis, after 9 weeks, and after 3-, 6- and 12 months. The main questions that the trial aims to answer are if the BA-treatment has an effect in the short and long term on: * Depressive symptoms * Anxiety symptoms * Self-rated activation * Self efficacy * Mental wellbeing * Quality of life * Cancer recurrence and survival