Local mental health services provide varying levels of intervention and support within a community setting, aiming to avoid residential care up until the point at which it is considered to be absolutely necessary and appropriate. Mental health treatment was shaped significantly by the birth of the NHS in 1948, which became the main health care provider in England. The slow shift from the detention of those with mental disorders to prevention and treatment (which began in the 1920s) continued under the newly formed NHS, as a further shift from institutionalisation to community-based care began.