BACKGROUND: Although mental health concerns are known to occur commonly for those with inflammatory bowel diseases (IBD), the nature of this comorbid relationship has not been systematically reviewed to date. A review in 2007 identified 5 controversies regarding anxiety/depression rates and various comparators between and within IBD. We aimed to systematically analyze and critique the current evidence regarding this comorbidity, providing an update to the 5 controversies. METHODS: Ebscohost Medline, CINAHL, Embase, and PsychINFO were searched between 2005 and 2014 using systematic review methodology. Controlled quantitative studies examining either symptoms or diagnoses of anxiety and depression in IBD were included in the review, with study quality assessed using a scale developed a priori to evaluate observational research. RESULTS: (1) IBD versus healthy controls (pooled mean proportions) (n = 13 studies): anxiety 19.1% versus 9.6%, depression 21.2% versus 13.4%; (2) IBD inactive versus IBD active disease (n = 26): anxiety 28.2% versus 66.4%, depression 19.9% versus 34.7%; (3) ulcerative colitis versus Crohn's disease (n = 28): anxiety 31% versus 37%, depression 22% versus 24.4%; (4) IBD versus other chronic medical conditions (n = 17): anxiety 41.9% versus 48.2%, depression 14.5% versus 28.4%; (5) onset of anxiety/depression before or after IBD onset (n = 2): adults more likely to develop anxiety/depression before IBD onset, but a substantial proportion develops depression after onset; an increased risk for children of developing anxiety/depression after IBD onset. CONCLUSIONS: The high rates of anxiety and depression for those with IBD, particularly when disease is active, warrant a systemic approach to screening and treatment.