[1] Maastricht Univ, Dept Neuropsychiat & Psychol, S Limburg Mental Hlth Res & Teaching Network, EURON, NL-6200 MD Maastricht, Netherlands
[2] Open Univ, Dept Clin Psychol, Heerlen, Netherlands
[3] Catholic Univ Louvain, Dept Human Genet, Univ Hosp Gasthuisberg, B-3000 Louvain, Belgium
[4] Assoc Sci Res Multiple Births, Ghent, Belgium
[5] Inst Psychiat, Div Psychol Med, London, England