Depression is common in people with long-term physical conditions and those seen in medical settings. The actual prevalence varies according to the setting, type and severity of disease, the individual’s perception of their condition and premorbid risk factors (e.g. childhood adversity). Depression has a bi-directional causal relationship with physical disease, so each can be a risk factor for the other. Depression and anxiety symptoms co-occur more often than as separate conditions and are often undetected or diagnosed by primary and secondary healthcare staff. People who experience depression and physical illness understand depression as part of their whole life experience and not just as being simply related to their physical health. Depression, and to a lesser extent anxiety, in the context of physical disease are associated with a range of poor outcomes, including poorer physical health outcomes and quality of life; increased hospitalisations, investigations and healthcare costs; and higher mortality.