American Journal of Epidemiology Advance Access originally published online on September 12, 2006
American Journal of Epidemiology 2006 164(9):916-917; doi:10.1093/aje/kwj303
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Letter to the Editor |
RE: "FETAL GROWTH AND CHILDHOOD BEHAVIORAL PROBLEMS: RESULTS FROM THE ALSPAC COHORT"
1 Institute of Public Health, Department of Epidemiology, Aarhus University, Aarhus DK-8000, Denmark
2 Department of Pediatrics, Aarhus University Hospital-Skejby, Aarhus DK-8000, Denmark
3 Institute of Public Health, Department of Epidemiology, University of California Los Angeles, Los Angeles, CA 90095
(e-mail: co{at}soci.au.dk)
In a recent Journal paper, Wiles et al. (1
) studied the association of weight and length at birth with behavioral problems as measured by scores on the Strengths and Difficulties Questionnaire (SDQ) (2). They found that every standard deviation in birth length at term reduced the risk of being in the higher tertile of the parents' SDQ reports about their children.
SDQ scores in populations have an asymmetrical distribution with a large proportion of low scores. These scores are usually dichotomized in the analyses, but the cutoff level varies, which makes comparisons of results a challenge. The SDQ data from the ALSPAC study have been analyzed in several reports. In the first studies by O'Conner et al. (3–5), a high score was defined by two standard deviations above the mean for each gender; Ramchandani et al. (6) used a more conservative approach, with a focus on the upper 10 percent; whereas Wiles et al. (1) used the upper tertile. The use of a 10 percent cutoff in a United Kingdom population may be the most obvious a priori choice because we have data on how this part of the distribution relates to psychopathology (7). The higher third percentile on the SDQ will include a large fraction of children with normal behavior. We therefore encourage the authors to present the association between birth length and SDQ score with a cutoff above an upper 10 percent.
Wiles et al.'s result (1) may reflect a causal association between behavioral problems and fetal growth restriction, but genetic confounding is another possibility because length at birth is influenced by both genetic and environmental factors. The association found could reflect a genetic link between behavioral problems and stature, as we have seen for intelligence quota (8).
In the Danish Aarhus Birth Cohort, data on maternal height were collected during pregnancy (9). When the children born in 1990–1992 were 10–12 years of age, mothers were asked to report on their own attention/hyperactivity behavior at the time they were of school age (complete follow-up rate: 52 percent). We used the score for the five SDQ items referring to their own time in school and found that being tall was associated with a lower risk of having a high score (figure 1; test for trend for both conventional cutoffs, p < 0.01). We acknowledge that the validity of this self-reported information on previous behavior can be questioned. We also accept that the association may reflect fetal programming of a mother's behavioral problems by her own fetal growth impairment that again may influence her postnatal growth. Still, there may be a common genetic link between height and behavioral problems. It would be interesting to see the results reported by Wiles et al. (1) adjusted for parental height.
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ACKNOWLEDGMENTS
Conflict of interest: none declared.
References
- Wiles NJ, Peters TJ, Heron J, et al. Fetal growth and childhood behavioral problems: results from the ALSPAC cohort. Am J Epidemiol 2006;163:829–37.
[Abstract/Free Full Text] - Goodman R. The Strengths and Difficulties Questionnaire: a research note. J Child Psychol Psychiatry 1997;38:581–6.[Web of Science][Medline]
- O'Connor TG, Heron J, Golding J, et al. Maternal antenatal anxiety and children's behavioural/emotional problems at 4 years: report from the Avon Longitudinal Study of Parents and Children. Br J Psychiatry 2002;180:502–8.
[Abstract/Free Full Text] - O'Connor TG, Heron J, Glover V. Antenatal anxiety predicts child behavioral/emotional problems independently of postnatal depression. J Am Acad Child Adolesc Psychiatry 2002;41:1470–7.[CrossRef][Web of Science][Medline]
- O'Connor TG, Heron J, Golding J, et al. Maternal antenatal anxiety and behavioural/emotional problems in children: a test of a programming hypothesis. J Child Psychol Psychiatry 2003;44:1025–36.[CrossRef][Web of Science][Medline]
- Ramchandani P, Stein A, Evans J, et al. Paternal depression in the postnatal period and child development: a prospective population study. Lancet 2005;365:2201–5.[CrossRef][Web of Science][Medline]
- Goodman R. Psychometric properties of the strengths and difficulties questionnaire. J Am Acad Child Adolesc Psychiatry 2001;40:1337–45.[CrossRef][Web of Science][Medline]
- Johnson FW. Biological factors and psychometric intelligence: a review. Genet Soc Gen Psychol Monogr 1991;117:313–57.[Web of Science][Medline]
- Kristensen J, Vestergaard M, Wisborg K, et al. Pre-pregnancy weight and the risk of stillbirth and neonatal death. BJOG 2005;112:403–8.[Web of Science][Medline]
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  N. J. Wiles, T. J. Peters, J. Heron, D. Gunnell, A. Emond, and G. Lewis THE AUTHORS REPLY Am. J. Epidemiol., November 1, 2006; 164(9): 917 - 917. [Full Text] [PDF]
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