Beyond the Group Mean: Individual Response Heterogeneity in Social Appearance Anxiety, Anxiety and Interpersonal...

Background/Objectives: The psychological consequences of elective aesthetic surgery are usually evaluated by comparing group means, an approach that is insensitive to change that differs in direction across individuals. This prospective controlled study examined both group-level and individual-level psychological change following aesthetic surgery. Methods: Forty adults undergoing elective aesthetic procedures and thirty-nine comparison participants completed the Social Appearance Anxiety Scale (SAAS), an anxiety inventory, and the Interpersonal Relationships Dimensions Scale (IRDS) at baseline and three months later. Analyses comprised mixed-design repeated-measures ANOVA, linear mixed-effects models, Aligned Rank Transform ANOVA, two one-sided equivalence tests, Bayes factors, variance-of-change comparisons, three-month stability coefficients, and Reliable Change Index classification. Results: At baseline the surgical group reported higher anxiety (d = 0.61) and a distinct interpersonal profile, with markedly higher approval dependence (d = 1.64) and lower empathy (d = -1.46) and emotional awareness (d = -0.58). No time × group interaction was significant under any analytic framework (all FDR-adjusted p > 0.67). Equivalence testing established that differential effects larger than d = 0.64 could be excluded for five of seven outcomes, while Bayes factors provided only moderate support for the null (BF₀₁ = 2.05-4.28). Individual-level analyses told a different story. The variance of change was 2.3 to 51.8 times larger in the surgical group (all FDR p < 0.05), three-month stability was substantially lower in the surgical group on six of seven outcomes, and 72.5% of surgical patients showed reliable change on at least one outcome compared with 12.8% of controls (p < 0.001), with reliable improvement (25.0%) and reliable deterioration (30.0%) occurring in broadly comparable proportions. Conclusions: The surgical group showed substantially greater variability in individual psychological trajectories than the comparison group despite the absence of differential group-mean change. These exploratory findings are compatible with possible individual response heterogeneity but should not be interpreted as evidence that aesthetic surgery itself caused psychological improvement or deterioration. Future research should examine whether preoperative characteristics can help identify patients who may be more likely to experience unfavorable psychological trajectories.