Cognitive impairment and clinical correlates in Chinese adolescents with major depressive disorder: a case-control study using the THINC-it tool

Cognitive impairment is increasingly recognized as an important clinical feature of major depressive disorder (MDD), but evidence in adolescents remains limited. The THINC-integrated tool is a brief digital cognitive assessment battery that may be useful for evaluating cognitive dysfunction in psychiatric settings. This study examined THINC-it performance and its clinical correlates in Chinese adolescents with MDD. This cross-sectional case-control study included 94 adolescents with MDD and 100 healthy controls. Analyses used the application-generated THINC-it index scores recorded in the source dataset. Group differences were examined using Mann-Whitney U tests with Bonferroni correction and median regression adjusted for age, sex, and educational level. Spearman correlations were used to evaluate associations of depressive and anxiety symptoms, HAMD factors, and demographic and clinical variables with cognitive performance. Adolescents with MDD had significantly lower scores than healthy controls across all five THINC-it domains after Bonferroni correction. Adjusted median regression confirmed lower CRT, DSST, TMT, and PDQ-5-D scores in the MDD group, whereas the confidence interval for N-back included zero. Both HAMD and HAMA total scores showed modest negative correlations with CRT after correction (HAMD: ρ = -0.290, adjusted P = 0.023; HAMA: ρ = -0.325, adjusted P = 0.007). The two dependent correlations did not differ significantly (Williams test, P = 0.745). No HAMD factor or additional demographic or clinical correlate remained significant after false-discovery-rate correction. Chinese adolescents with MDD showed broadly lower THINC-it index scores, particularly for subjective cognition, reaction speed, and processing speed. Depressive and anxiety symptom severity were each modestly associated with lower CRT performance, without evidence that one association was stronger than the other. These findings support further evaluation of THINC-it in adolescents but do not establish its clinical utility or adolescent-specific validity.