The mediating role of intolerance of uncertainty on the relationships between perfectionism dimensions and psychological adjustment/maladjustment among mothers

- IU suppressed the relationships between PS and adjustment/maladjustment.
- The suppression effects of IU were found only when CM was not partialled out.
- IU mediated the relationships between CM and adjustment/maladjustment.
- Mediation effects of IU were found regardless of whether PS were partialled out.
- Common effects of PS and CM explained 12.3% of the variance in IU.

The present study investigated a possible mediating effect of intolerance of uncertainty (IU) on the relationship between perfectionism and psychological adjustment/maladjustment as well as the unique and common effects of perfectionism dimensions-personal standards (PS) and concern over mistakes (CM)-on these constructs. Five hundred mothers participated an online survey, completing measures of perfectionism (PS and CM), IU, and psychological adjustment/maladjustment (life satisfaction, depression, and rearing stress). We found that both PS and CM were positively correlated with IU. Mediation analyses indicated that IU mediated the relationship between CM and psychological adjustment/maladjustment regardless of whether PS were partialled out. In contrast, IU had a suppression effect on the relationship between PS and psychological adjustment/maladjustment, but only when CM was not partialled out. Commonality regression analysis revealed that the unique effect of PS on IU (< 0.1%) was much smaller than the common effects of PS and CM on IU (12.3%). In addition, CM had stronger unique effects on all variables than did PS. These findings highlight the importance of investigating both the unique and common effects of perfectionism dimensions on outcome variables. Our findings further our understanding of the mechanisms underlying the relationships between perfectionism dimensions and psychological adjustment/maladjustment.