The degree to which early adverse experiences exert long term effects on development and how much early adversity may be overcome through subsequent experiences are important mental health questions. The clinical, research and policy perspectives on these questions lead to different answers. From a clinical perspective, change is always possible, and it is never too late. From a research perspective, there are data indicating that there are sensitive periods in brain development, which may constrain subsequent adaptability. From a policy perspective, there is a growing consensus that early intervention is cost effective from the standpoint of child development, neuroscience and economic research.