Background: David Farrington (1944-2024) wrote extensively about the methodological rigour and utility of the longitudinal-experimental research design to advance knowledge about the development, explanation, prevention and treatment of antisocial behaviour and criminal offending over the life-course. Founded in 1935, the Cambridge-Somerville Youth Study (CSYS) is recognised as the first randomised controlled trial in criminology and the first longitudinal-experimental study in criminology.
Aims: To report on key scientific and policy contributions made by the CSYS in investigating the development and prevention of delinquency and criminal offending over the life-course.
Methods: Uses previously analysed observational and experimental data from follow-ups of study participants conducted in middle age (N = 494; mean = 47 years) and old age (N = 488; 84-92 years).
Results: Identified several parental socialisation practices and interactions during childhood (but not father absence) as strongly associated with serious criminal offending in middle age. Support for peer deviancy as a causal mechanism for iatrogenic effects among treatment groups, compared to pair-matched controls, during middle age drew policy attention to group-based prevention interventions.
Conclusions: The longitudinal-experimental design is a highly important yet under-utilised methodological approach in criminology. Future research should include revisiting the original plan for the design, addressing a key potential concern of the design and carrying out longer follow-ups at key stages of the life-course.