“…Comparability of the pre-post cohorts was difficult to assess in 10 studies (Boyd & Stuart, 2005;Eisen & Amiel, 2007;Habich & Letizia, 2015;Jadav et al, 2009;LeMay et al, 2009;LeMay et al, 2010;Newstead et al, 2013;Porter et al, 2015;Ramira et al, 2016;Taylor et al, 2013) because baseline characteristics were inadequately reported, inequality in group diagnoses, age or causation of pain and/or the small numbers of participants recruited. Ten studies reported consecutive participant selection (Boyd & Stuart, 2005;Hawkes et al, 2008;Iyer et al, 2011;Jadav et al, 2009;Kaplan et al, 2008;Porter et al, 2015;Ramira et al, 2016;Scott et al, 2013;Somers et al, 2001;Williams et al, 2012) while in the remaining studies the selection process was unclear, or numbers too small to be representative of the population.…”