which suggested a strong association between cannabis use and lung cancer in young adults. Additionally, the lifetime exposure of older individuals would be expected to be much lower as they would have been older than the typical age for onset of use when the ‘‘epidemic’’ of cannabis use began in the 1960s. Due to the low incidence of lung cancer in this age group, representing,10% of all lung cancers [23], cases diagnosed up to 5 yrs before interview were included. No information from deceased cases was sought. If survival after diagnosis was different for users compared with nonusers of cannabis, this may have influenced the results obtained. Cases were identified from both the
National Cancer Registry and from hospital outpatient and discharge databases to ensure case ascertainment was as complete as possible