There is no question more fundamental for observational epidemiology than that of causal inference. When, for practical or ethical reasons, experiments are impossible, how may we gain insight into the causal relationship between exposures and outcomes? This is the key question that Quinn et al1 seek to answer: does maternal smoking during pregnancy (SDP) cause offspring serious mental illness (SMI)?
Kendler KS. Causal Inference in Psychiatric Epidemiology. JAMA Psychiatry. Published online May 03, 2017. doi:10.1001/jamapsychiatry.2017.0502