Results of search (PRISMA flow diagram)

<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0050691#pone.0050691-Moher1" target="_blank">[43]</a><b>.</b> N refers to the number of studies. Among the studies that measured the outcomes of interest, some could fall into more than 1 category. Note that a total of 144 studies were excluded because models were not dynamic.