apparent effects we estimated. We considered early-life exposures measured prior to measurement of conduct problems in an attempt to address issues of reverse causation. It is possible that some of these exposures, for example maternal substance use, persisted beyond the early life-course. Because of this, any inference on specific effects of early-life exposure on later outcomes must be cautious. Our sample was aged mainly 16 years at the time they completed our questionnaire. Problem cannabis use phenotypes might not have emerged fully by this point of the life-course and we might have identified risk factors for cannabis problems apparent relatively early in the life-course rather than cannabis problems in general.
