An aspect of IBD care that is often overlooked is mental health treatment. Common mental health problems, such as anxiety and depression are very common in IBD, with a meta-analysis estimating prevalence as high as 25.2% for depression and 32.1% for anxiety. The prevalence of anxiety and depression increases when individuals with active disease are considered, with rates as high as 57.6% for anxiety and 38.9% for depression. Comorbid depression and anxiety in IBD is associated with greater symptom severity, even when statistically controlling for disease activity; more frequent and expensive emergency department visits and inpatient stays, higher costs relating to IBD-related surgery, medication and personal expenditure; noncompliance with medical treatment and finally, increased likelihood of experiencing flares. However, very few studies attempt to unpick the precise mechanism of these bidirectional relationships. Indeed, depression and anxiety may have direct effects on physical health through inflammatory or psychoneuroimmunological pathways. Very few studies investigate the longitudinal brain-gut relationship with regards to objective measures of inflammation. Additionally, the indirect effects of mental health are often overlooked. Depression and anxiety are routinely associated with health behaviours, such as diet, physical activity, sleep, and tobacco/alcohol use.These health behaviours are important factors, given their impact on physical health outcomes. Therefore, a thorough investigation is required to ascertain the precise mechanisms that underpin the bidirectional relationship between depression/anxiety and inflammation/physical health, as this will enable practitioners and researchers to establish non-invasive, behavioural treatment targets for this patient group. AIM The broad aim of this project is to explore whether anxiety/depression has a direct or indirect (via health behaviours) on i) inflammation levels ii) clinical activity and iii) healthcare usage at follow-up, in a population of IBD patients. A secondary aim of the project will be to explore whether changes in disease activity, as measured by self-report measures and faecal calprotectin, explains changes in anxiety and depression symptoms at follow up.