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Parental income during childhood associated with subsequent schizophrenia risk

Christian Hakulinen

Children who grow up in low-income conditions have a greater risk for schizophrenia, and upward income mobility was associated with a lower risk for schizophrenia compared with downward mobility, according to a study of a Danish cohort published in JAMA Psychiatry.

“We found that the longer a person spent living in low-income conditions during childhood, the higher the subsequent risk for schizophrenia,” Christian Hakulinen, PhD, of the department of psychology and logopedics at the University of Helsinki in Finland, told Healio Psychiatry. “Second, we found that regardless of parental income level at birth, upward income mobility between birth and age 15 was generally associated with a lower risk for schizophrenia.”

Previous research investigating potential links between parental socioeconomic position and child’s schizophrenia risk has reported inconsistent findings. Further, this risk’s association with parental socioeconomic mobility had yet to be investigated, according to the researchers.

Hakulinen and colleagues conducted a national cohort study of all individuals born in Denmark between January 1980 and December 2000. They followed these individuals from age 15 until schizophrenia diagnosis, emigration, death or until Dec. 31, 2016, whichever came first. They determined parental income at birth year and at ages 5, 10 and 15 years.

Of more than 1 million participants, 7,544 were diagnosed with schizophrenia during 11.6 million person-years of follow-up.

The researchers reported an inverse association between parental income during childhood and subsequent risk for schizophrenia, with cohort members from families in the lowest income quintile more likely to be diagnosed with the disorder (HR = 2.86; 95% CI, 2.65-3.08). The association remained after adjusting for parental mental illness, degree of urbanization, parental educational attainment level and the number of changes in child-parent separation status. They also noted that upward income mobility between birth and age 15 years, regardless of parental income level at birth, resulted in a general association with a lower risk for developing schizophrenia. For instance, participants whose families rose from income quintile 1 to 5 between birth and age 15 years, the risk was substantially reduced (HR = 1.61; 95% CI, 1.32-1.97). Conversely, downward income mobility predicted higher risks.

“We were surprised when we saw that the trend in our results was so clear as previous studies have showed mixed findings, and our findings highlight the importance of early family socioeconomic environment in the development of schizophrenia,” Hakulinen said.

In a related editorial, Richard G. Frank, PhD, the Margaret T. Morris Professor of Health Economics at Harvard University, highlighted a direction for further research.

“Natural experiments that examine contexts in which various types of income supports and child supports are available to similar risk populations can begin a program of inquiry that can yield important insights into key policy design parameters,” Frank wrote. “That job in the United States would be facilitated if we followed the Danish example and increased investments that permit administrative data to be linked and used to take on such questions.” – by Joe Gramigna

Disclosures: The authors report no relevant financial disclosures.