title: ORCHIDS: an observational randomized controlled trial on childhood differential susceptibility.
abstract: BACKGROUND
  A central tenet in developmental psychopathology is that childhood rearing experiences have a major impact on children's development. Recently, candidate genes have been identified that may cause children to be differentially susceptible to these experiences (i.e., susceptibility genes). However, our understanding of the differential impact of parenting is limited at best. Specifically, more experimental research is needed. The ORCHIDS study will investigate gene-(gene-)environment interactions to obtain more insight into a) moderating effects of polymorphisms on the link between parenting and child behavior, and b) behavioral mechanisms that underlie these gene-(gene-)environment interactions in an experimental design.
  
  
  METHODS
  The ORCHIDS study is a randomized controlled trial, in which the environment will be manipulated with an intervention (i.e., Incredible Years parent training). In a screening, families with children aged 4-8 who show mild to (sub)clinical behavior problems will be targeted through community records via two Dutch regional healthcare organizations. Assessments in both the intervention and control condition will be conducted at baseline (i.e., pretest), after 6 months (i.e., posttest), and after 10 months (i.e., follow-up).
  
  
  CONCLUSIONS
  This study protocol describes the design of a randomized controlled trial that investigates gene-(gene-)environment interactions in the development of child behavior. Two hypotheses will be tested. First, we expect that children in the intervention condition who carry one or more susceptibility genes will show significantly lower levels of problem behavior and higher levels of prosocial behavior after their parent(s) received the Incredible Years training, compared to children without these genes, or children in the control group. Second, we expect that children carrying one or more susceptibility genes will show a heightened sensitivity to changes in parenting behaviors, and will manifest higher emotional synchronization in dyadic interchanges with their parents. This may lead to either more prosocial behavior or antisocial behavior depending on their parents' behavior.
  
  
  BACKGROUND
  Dutch Trial Register (NTR3594).
authors.affiliation: Department of Developmental Psychology, Utrecht Centre for Child and Adolescent Studies, Utrecht University, PO Box 80,140 Utrecht, 3508 TC The Netherlands.
authors.forename: Rabia R
authors.initials: RR
authors.lastname: Chhangur
authors.forename: Joyce
authors.initials: J
authors.lastname: Weeland
authors.forename: Geertjan
authors.initials: G
authors.lastname: Overbeek
authors.forename: Walterchj
authors.initials: W
authors.lastname: Matthys
authors.forename: Bram
authors.initials: B
authors.lastname: Orobio de Castro
mesh_terms: D002648:Child; D002653:Child Behavior Disorders / Q000235:genetics*; D002675:Child, Preschool; D005500:Follow-Up Studies; D059647:Gene-Environment Interaction; D020022:Genetic Predisposition to Disease; D006801:Humans; D009426:Netherlands; D010287:Parent-Child Relations; D016487:Parenting / Q000523:psychology*; D010290:Parents / Q000193:education* / Q000523:psychology; D011110:Polymorphism, Genetic; D012107:Research Design