Food and Behaviour Research

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Association between immigrant background and ADHD: a nationwide population-based case-control study.

Lehti V, Chudal R, Suominen A, Gissler M, Sourander A. (2016) J Child Psychol Psychiatry.  May 2. doi: 10.1111/jcpp.12570. [Epub ahead of print] 

Web URL: View this and related abstracts via PubMed here.

Abstract:

BACKGROUND:

Information about psychiatric disorders among those with immigrant parents is important for early detection and service development. The aim of this study is to examine the association between parental immigration and the diagnosis of attention-deficit hyperactivity disorder (ADHD) in offspring in Finland.

METHODS:

This matched case-control study was based on a national birth cohort. The sample included all singletons who were born in Finland in 1991-2005 and diagnosed with ADHD by the year 2011 (n = 10,409) and their matched controls (n = 39,124). Nationwide registers were used to identify participants and to gather information on the parents' country of birth and native language. Conditional logistic regression analyses were conducted using maternal and paternal migration status and region of birth as well as time since maternal migration as exposure factors.

RESULTS:

The likelihood of being diagnosed with ADHD was significantly increased among children of two immigrant parents [adjusted odds ratio (aOR) 4.7, 95% CI 3.4-6.6] and children of an immigrant father (aOR 1.9, 95% CI 1.6-2.2).

The likelihood of receiving an ADHD diagnosis was equal among children whose mother was a recent immigrant when she gave birth and those whose mother had stayed in Finland at least for a year before birth.

The association between parental migration and ADHD diagnosis was strongest among fathers born in sub-Saharan Africa or Latin America and among mothers born in sub-Saharan Africa or North Africa and Middle East. Children, whose parents were born in countries with low Human Development Index (HDI), were more often diagnosed with ADHD.

CONCLUSIONS:

The increased likelihood of ADHD diagnosis among children of immigrants indicates increased exposure to environmental risk factors, differences in the use of health services, or challenges in diagnosing immigrants' children.

© 2016 Association for Child and Adolescent Mental Health.

FAB RESEARCH COMMENT:

Many studies show increased rate of psychiatric disorders in the children of 'immigrant' parents.

Clearly, there are numerous possible factors that could help to explain these findings, but one that has been attracting increasing attention (not least because it would be relatively simple and cheap to modify compared with most others) is the potential role of Vitamin D in brain development and function. Obviously this would be particularly relevant with respect to darker-skinned immigrants living in countries with limited exposure to bright sunshine, as in the current study.

In animals, even transient Vitamin D deficiency during pregnancy leads to permanent changes in brain structure and function in the offspring, affecting perception, movement, behaviour and cognition. Furthermore, these changes in brain and nervous system reactivity are consistent with those associated with many psychiatric conditions, including autism, ADHD and schizophrenia.

Increasing evidence now links low maternal Vitamin D status in humans to these and other developmental and mental health conditions. Large scale trials of supplementation during pregancy - with long-term follow-up - are obviously needed to provide definitive evidence that Vitamin D plays a causal role in neuropsychiatric disorders in humans.  However, given the many physical health benefits of adequate Vitamin D in early life, there are already good grounds for mandatory supplementation or fortification in most developed countries.

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