What can siblings and cousins tell us about the role of early life family income in the aetiologies of violent crime, substance misuse and psychiatric morbidity?

In our recent paper,[1] we examined associations between family income during childhood and adolescence on subsequent risks of developing psychiatric disorders, having substance misuse problems and being arrested for a violent crime. In fact, the point estimates for the sibling-comparison estimates were all close to 1, indicating no difference between the siblings regardless of their family income exposure, and the confidence intervals were narrow, indicating a high level of precision of the estimates. [Extracted from the article]