“…However, not all studies are positive (Boutros et al, 2002;Cohen et al, 2003;Hansen et al, 2004;Hausmann et al, 2004;Loo et al, 1999;Loo et al, 2003;Mosimann et al, 2004) and earlier studies were hampered by small sample sizes and other limitations. A recent meta-analysis argues that the improved design (dose, length of treatment) of recent studies (Avery et al, 2006;Fitzgerald et al, 2003Fitzgerald et al, , 2006 is associated with larger treatment effects than work before 2000 (Gross et al, 2007).…”