Restriction of range effects in post–metabolic and bariatric surgery outcomes research: considerations for clinical decision making

Preoperative psychopathology does not consistently predict postoperative outcomes in patients who undergo metabolic and bariatric surgery (MBS). Individuals with elevated pre-MBS psychopathology may be less likely to undergo surgery, which may create a floor effect given the limited range of scores on measures of psychopathology included in postoperative analyses, thereby decreasing the power to detect clinically significant differences between groups. Our objective was to compare rates of clinically significant pre-MBS psychopathology across domains of functioning in patients who did and did not undergo MBS: surgical completers (SCs, n = 286) and nonsurgical completers (NSCs, n = 125). Academic medical center, United States. Participants (n = 411) were a racially diverse sample of MBS candidates who completed a preoperative psychosocial evaluation including measures of disordered eating, alcohol and tobacco use, pain catastrophizing, anxiety, and depressive symptomatology. Compared with SCs, NSCs had larger scale score variance on measures of psychopathology and were more likely to be Black; to report clinically significant scores on measures of binge eating, depression, anxiety, and pain catastrophizing; and to use tobacco. Results support the presence of a restriction-of-range effect but do not demonstrate a floor effect. These data suggest that current outcome data for MBS patients may not generalize to those who report clinically significant psychopathology at the pre-MBS psychosocial evaluation and may warrant caution when using the current literature to inform clinical decision making for this group. Findings also suggest a need for interventions that will better engage Black patients. •Pre-surgical pathology does not reliably predict post-bariatric surgery outcomes.•Clinically significant psychopathology is less prevalent among surgical completers.•Restricted range effects in bariatric outcomes research may impact decision-making.