Early predictors of behavioural problems in pre-schoolers - a longitudinal study of constitutional and environmental main and interaction effects.
The early environment is important for child development and wellbeing. Gene-by-environment studies investigating the impact of the serotonin transporter gene-linked polymorphic region (5-HTTLPR) and the Brain Derived Neurotrophic Factor (BDNF) Val66Met polymorphisms by life events on mental health and behaviour problems have been inconclusive. Methodological differences regarding sample sizes, study population, definitions of adversities and measures of mental health problems obstacle their comparability. Furthermore, very few studies included children. The aim of this study was to examine the associations between a broad range of risk factors covering pregnancy and birth, genetic polymorphism, experience of multiple life events and psychosocial environment, and child behaviour at age 3, using a comparably large, representative, population-based sample.



A total of 1,106 children, and their mothers, were followed from pregnancy to age 3. Information on pregnancy and birth-related factors was retrieved from the Medical Birth Register. Questionnaires on depressive symptoms, child behaviour and child experiences of life events were filled in by the mothers. Child saliva samples were used for genotyping the 5-HTTLPR and BDNF Val66Met polymorphisms. Multiple logistic regression was used to investigate the association between psychological scales and genetic polymorphisms.



Symptoms of postpartum depression increased the risk of both internalizing and externalizing problems. Experience of multiple life events was also a predictor of behavioural problems across the scales. No gene-by-environment or gene-by-gene-by-environment interactions were found. Children of immigrants had an increased risk of internalizing problems and parental unemployment was significantly associated with both internalizing and externalizing type of problems.



This study shows the importance of the psychosocial environment for psychosocial health in preschool children, and adds to the literature of null-findings of gene-by-environment effects of 5-HTTLPR and BDNF in children.
Division of Child and Adolescent Psychiatry, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, SE-581 85, Linköping, Sweden. sara.agnafors@liu.se.
Sara
S
Agnafors
Division of Obstetrics and Gynaecology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, SE-581 85, Linköping, Sweden.
Gunilla
G
Sydsjö
Department of Neuroscience, Uppsala University, SE-751 24, Uppsala, Sweden.
Erika
E
Comasco
Division of Obstetrics and Gynaecology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, SE-581 85, Linköping, Sweden.
Marie
M
Bladh
Department of Neuroscience, Uppsala University, SE-751 24, Uppsala, Sweden.
Lars
L
Oreland
Division of Child and Adolescent Psychiatry, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, SE-581 85, Linköping, Sweden.
Carl Göran
CG
Svedin
D019208:Brain-Derived Neurotrophic Factor / Q000235:genetics; D002653:Child Behavior Disorders / Q000175:diagnosis / Q000209:etiology*; D002675:Child, Preschool; D005260:Female; D059647:Gene-Environment Interaction; D005819:Genetic Markers; D020022:Genetic Predisposition to Disease; D006801:Humans; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D015999:Multivariate Analysis; D011110:Polymorphism, Genetic; D012307:Risk Factors; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics; D012931:Social Environment
D019208:Brain-Derived Neurotrophic Factor; D005819:Genetic Markers; C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins; C579455:BDNF protein, human
Behaviour; Gene-by-environment; Longitudinal; SESBiC-study; Socio-environment