Using natural experiments and animal models to study causal hypotheses in relation to child mental health problems

There is enormous interest in identifying causes of child psychopathology but considerable difficulty in knowing which risks are genuinely causal and in showing how they work. Why is it such a problem and how might we go about testing causal hypotheses? In this chapter we first discuss the threats that clinicians and researchers face in making causal inferences from traditional observational designs, explain why natural experiments are useful and what they are. The focus will be on the growing range of different types of natural experiment, with the emphasis on principles and strategy, assumptions and limitations. We then adopt a similar approach to animal models designed to study environmental and genetic risks with an emphasis on the concepts, principles and experimental strategies.