Statistical geneticists at HSPH develop statistical methods for understanding the genetic basis of human diseases and traits. These methods involve large-scale data sets from candidate-gene, genome-wide and resequencing studies, using both unrelated and related individuals. HSPH statistical geneticists collaborate with other investigators at HSPH and around the world on studies of cancer, heart disease, diabetes, respiratory disease, psychiatric disease, and health-related behaviors (e.g. smoking, diet). Review article comes in the form of systematic reviews and literature reviews and are a form of secondary literature. Systematic reviews determine an objective list of criteria, and find all previously published original research papers that meet the criteria. They then compare the results presented in these papers. Literature reviews, by contrast, provide a summary of what the authors believe are the best and most relevant prior publications. The concept of "review article" is separate from the concept of peer-reviewed literature. It is possible for a review to be peer-reviewed, and it is possible for a review to be non-peer-reviewed.