Intestinal parasites may be associated with later behavioral problems in internationally adopted children

Aim At arrival in new home country, internationally adopted children often have intestinal parasites. International adoptees also exhibit more behavioral problems than their biological peers. We examined whether intestinal parasite infections in international adoptees on arrival in Finland are associated with their later behavioral and emotional problems. Methods Data for this study were sourced from the Finnish Adoption Study (FinAdo) based on parental questionnaires for all internationally adopted children under 18 years (n = 1450) who arrived in Finland from 1985 to 2007. A total of 1293 families provided sufficient information on the adoptee’s background, parasitic status on arrival, and behavioral symptoms at the median time of 5 years after arrival (mean age = 7.8 years). Behavioral and emotional disorders were evaluated with the Child Behavior Checklist (CBCL). Statistical analyses were conducted using linear regression. Results Of the 1293 families, parents of 206 adoptive children reported intestinal parasites in their adopted children on arrival. Parasite-infected children had subsequently higher CBCL problem scores than the children without parasites (p < 0.001). The association between intestinal parasites and later behavioral problems was stronger than that between intestinal parasites and any other factors measured in this study, except disability. Limitations The control group was naturally provided by the adopted children without parasite infections, but we could not compare the adopted children to non-adopted children without a defined parasite infection. We were unable to specify the effects associated with a specific parasite type. It was not possible either to include multiple environmental factors that could have been associated with behavioral problems in the models, which indicated only modest explanatory values. Conclusions In this study, intestinal parasite infections in early childhood may be associated with children’s later psychological wellbeing, even in children who move to a country with a low prevalence of parasites. Our findings may support further developments pertaining to the gut-brain theory.

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Dear Editor-in-Chief, I wish to submit the digital version of our manuscript entitled "Intestinal parasites associated with later behavioral problems in internationally adopted children." I hope you will find this research article interesting enough to be considered for publication in PLOS One.
Many recent studies have shown that intestinal parasites are common among internationally adopted children at the time of arrival in their new home country. Internationally adopted children also often display behavioral symptoms after arrival and later in their life. In this study, we assessed whether intestinal parasitic infections in early childhood are somehow associated with psychiatric symptoms later in the lives of the infected children. To the best of our knowledge, this research study is the first one to discover such an association even when the studied internationally adopted children move to the new country with a low prevalence of intestinal parasites and parasitic infections. The reason behind this association is not known. We suggest that these results may be attributed to intestinal parasites modulating intestinal microbiota and thereby impacting the children's developing brains through the microbiota-gut-brain axis.
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I look forward to hearing from you. Intestinal parasites associated with later behavioral 4 problems in internationally adopted children       The child's gender, age at adoption, age at evaluation, and country of birth 102 were reported by the parents. The type and number of placements before adoption were 103 classified into three categories for statistical analysis. The place of origin was categorized 104 by continent and region. Parents were also asked about any medical diagnoses their 105 children received from Finnish medical evaluations soon after arrival or later.

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Growth values of adopted children at arrival were reported in the parental 107 questionnaire. For the analysis growth values were expressed as z-scores, which were 108 compared against the growth charts of the World Health Organization (36). Weight-for- 109 age, height-for-age, and head circumference-for-age were used separately for both 110 genders. The z-scores ranged from -6 SD to +3 SD for weight, from -6 SD to +2.5 SD for 111 height, and from -5 SD to +3 SD for head circumference. Children with missing growth 112 values were excluded from the fourth step of the linear regression analysis. z-scores below 113 -2 SD in each category were considered to indicate delayed growth.  include conflict with others, such as rule-breaking or aggressive behavior (37). Each item 138 was rated as 0 (not true), 1 (somewhat or sometimes true), and 2 (very true or often true).

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The higher the child's scores in the CBCL, the greater the extent of his/her behavioral 140 problems.

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In this study we used two CBCL questionnaires: the CBCL for ages 1.5 to 5 142 years with 100 questions and that for ages 6 to 18 years with 113 questions (8). These

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Of the 1293 children screened, 206 had at least one intestinal parasite on 163 arrival in Finland (Fig 1), with Giardia lamblia being the most prevalent. Of the 206   Step 1, n = 1293 Step 2, n = 1285 Step 3, n = 1259 Step 4, n = 1069 Externalizin g problems impacts the developing brain through gut-brain axis.

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The use of antibiotics is also an alternative explanatory mechanism between  externalizing, and total score) is commonly applied in other research (7). In a former meta-281 analysis, the behavior problems of internationally adopted children were measured using 282 the CBCL, and the related measures showed only small differences between the 283 outcomes of the adopted children and non-adopted, parent-reared children (7). In this 284 study, the behavior of the internationally adopted children was evaluated using the CBCL 285 questionnaire at the time of evaluation, approximately 5 years after adoption. This finding 286 also underscores the importance brain development in the early years regardless of the 287 influence mechanism of the intestinal parasites.

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This study uncovered associations between an earlier intestinal parasite 289 infection and higher CBCL problem scores in all three CBCL categories (externalizing 290 problems, internalizing problems and CBCL total scores). The stronger association 291 observed in the older children may be due to their longer exposures to parasite infections.

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The association between the CBCL symptoms and the parasite infection in the children 293 adopted from South America may be due to the differences in the local parasites or the 294 different risk factors, such as being exposed to drugs in utero (4).

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This study was partly retrospective, as the health of the adopted children upon 296 their arrival in Finland was ascertained from their parents' responses to questions. The 297 time delay from the arrival date to these responses (approximately 5 years) may have 298 resulted in a bias. In general, however, the adoptive parents answered the questions 299 precisely and had good knowledge of the health and medical issues of their adopted 300 children because they had undergone substantial training before the adoption. This study 301 also tried to ascertain whether the studied children were anemic or had iron deficiency on 302 arrival, but doing so was not possible as their iron status was not registered.

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Earlier international studies using standardized measures such as the CBCL 304 to evaluate children coming from different continents suggest that no significant 305 differences exist in the extent or types levels of symptoms (47). Thus, the differences in 306 "normality" in behavior between various countries are rather small and difficult to evaluate.

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Similar to other studies, we used the CBCL as a continuous measure for the two border 308 groups and the total score (7). However, we were unable to determine specific cut-off 309 points for clinically relevant behavioral problems from these scores. However, such 310 measures have been shown to predict clinical outcomes. disability. This suggests that internationally adopted children should be screened for 322 intestinal parasites, and intestinal parasitism should be appropriately treated soon after 323 arrival, especially among these at-risk populations, as the children are typically undergoing 324 rapid growth and brain development at that age.