Ouellet-Morin I, Dionne G, Pérusse D, Lupien SJ, Arseneault L, Barr RG, Tremblay RE, Boivin M. Daytime cortisol secretion in 6-month-old twins: genetic and environmental contributions as a function of early familial adversity. Biol Psychiatry. 2009 Mar 01;65(5):409–16. doi: 10.1016/j.biopsych.2008.10.003. PMID: 19013558.