This 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 associations between childhood family income and later psychiatric disorders, substance misuse and violent crime. The consistency, strength and causal nature of these associations has been questioned by many scientists.
Professor Seena Fazel, Department of Psychiatry, University of Oxford, said:
'This study highlights the importance of high quality research designs in investigating links between childhood factors and later outcomes. The finding of no causal link between childhood family income and adult psychiatric disorders is potentially important as it suggests that simple interventions such as increasing family income on its own are unlikely to work – although this comes with the caveat that this work has been conducted in Finland, and replicates a previous family-based research study in Sweden.'
University researcher, Amir Sariaslan, University of Helsinki, explains:
'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.'
The researchers expected that the siblings who had been exposed to lower family income levels would have higher rates of the studied outcomes. 'This was not the case. We found that the siblings did not differ in their outcome rates regardless of the family income levels that they had been exposed to', said Professor Heikki Hiilamo, University of Helsinki.
The study concludes that interventions that primarily focus on improving parental earnings will unlikely lead to reductions in the rates of psychiatric disorders, substance misuse and violent crime arrests in their offspring. Whereas low family income may potentially be helpful in identifying families at risk, any specific interventions should target causal risk factors and be tested in high quality trials.
To read the full study (open access), No causal associations between childhood family income and subsequent psychiatric disorders, substance misuse and violent crime arrests: a nationwide Finnish study of >650,000 individuals and their siblings.
To read the full press release.