Previous research has found evidence of academic benefits to longer school years. This paper investigates one of the many potential costs of increased school year length, documenting a dramatic decrease in youth suicide in months when school is not in session. A detailed analysis does not find that other potential explanations such as economic conditions, weather or seasonal affective disorder patterns can explain the decrease. This evidence suggests that youth may face increased stress and decreased mental health when school is in session. (C) 2011 Elsevier Ltd. All rights reserved.