Cognitive–behavioural therapy can help patients cope with the challenges of living with mental and physical conditions. We have found that it consistently improves quality of life and reduces anxiety and pain symptoms for people living with many different conditions across the 19 ICD-11 categories for which we have systematic review evidence. CBT has been tested in many different populations and contexts, and all these reviews report effects that are consistent with our general effects. High- and low-intensity CBT appear to be equally effective. The biggest area of uncertainty is around whether sociological constructs, such as ethnicity, religion, culture, country or language, could moderate the effectiveness of CBT or whether it will be equally effective across these constructs. We suggest that CBT will be effective for the conditions represented in the ICD-11 codes we have represented in the overview. However, we are unclear if the general effect can be applied to conditions that are not represented at all in the overview.