A range of risk factors from early life measured prior to conduct problems were considered. These were derived from a number of questionnaires administered to the young person's parents between enrolment (early in antenatal period) and 47 months after the birth (i.e. up until the first measure of conduct problems). The choice of variables was parsimonious and was guided by considerations around the best use of available information on the possible influences discussed above, data completeness and collinearity. Previous work in ALSPAC found family position to be associated with adolescent alcohol use 17. Other than sex and family position (coded as whether study child is first/second/third child or greater) early-life risk factors were considered in the following categories.
