The Inventory of Interpersonal Problems (IIP): Sensitivity to change

Although the Inventory of Interpersonal Problems (IIP) is a standard instrument in both, psychotherapy research and quality control of psychotherapy, it's sensitivity to change has yet to be firmly established. The authors investigated the sensitivity to change of the IIP using a study design based on the assumption that psychoanalytic psychotherapy leads to significant improvement in interpersonal problems. To assess whether this type of change can be measured with the IIP, they did a pre/post comparison of IIP scores in 63 patients with depression. The authors evaluated therapeutic change by comparing means (t-test) and also by calculating standardized effect size (ES), the reliable change index and a measure of clinical significance (internal sensitivity to change). They also compared the IIP results with those of construct-near tests (external sensitivity to change). The IIP showed a satisfactory sensitivity to change, with highly significant differences on the t-test on all scales, an ES of 1.44 for the IIP total score and a large or medium ES (above 0.80 and 0.50, respectively) on most individual scales. Hence the IIP appears to be an appropriate instrument for assessing the effectiveness of psychotherapy.