Share Childhood family income has been shown to be associated with later psychiatric disorders, substance misuse and violent crime, but the consistency, strength and causal nature of these associations has been questioned by many scientists. A recent study of the entire population of Finland born between 1986 and 1996, comprising of over 650,000 individuals, including nearly 427,000 siblings within the sample, has re-examined these associations. “For each $15 000 increase in family income at age 15 years, the risks of the outcomes were reduced by between 9 % in severe mental illness and 23 % in violent crime arrests. However, these associations were fully attenuated in the sibling-comparison models”, university researcher Amir Sariaslan from University of Helsinki explains.