Machine learning-based screening model for Tic disorders comorbid with attention-deficit/hyperactivity disorder in children and SHAP value interpretation: a retrospective observational study

Tic disorders (TD) are common neurodevelopmental conditions in children and adolescents, characterized primarily by motor and vocal tics, with heterogeneous symptom presentations and significant fluctuations. Concurrently, attention-deficit/hyperactivity disorder (ADHD) is a highly prevalent comorbidity of TD, often exacerbating academic and emotional difficulties. However, due to the potential masking of ADHD symptoms by TD manifestations and insufficient awareness of comorbidities, ADHD diagnosis is frequently delayed. This study aimed to develop a machine learning-based classification model to identify children with TD who have a higher model-predicted probability of ADHD comorbidity, thereby potentially aiding diagnostic accuracy and treatment planning. The research was conducted by the Pediatrics Department of Guang'anmen Hospital, China Academy of Chinese Medical Sciences, from October 2023 to October 2024. A retrospective cohort of 1,364 children with TD was included, comprising 889 with TD alone and 475 with TD comorbid with ADHD. The dataset was divided into a training set and an independent test set using a stratified 7:3 split, with the random seed fixed at 42 to ensure the balance of baseline characteristics between the two groups. 10-fold cross-validation was used for hyperparameter tuning and preliminary performance evaluation within the training set, and the final model performance was verified on the independent test set. Twenty-eight clinical features were collected, encompassing general information, family factors, academic performance, medical history, emotional status, and sleep quality. Core variables were selected using Lasso regression, and five distinct machine learning models were constructed. Feature importance was interpreted using SHAP analysis. Ultimately, seven key features were identified for algorithm development: learning initiative, guardian type, academic performance, allergic rhinitis, irritability, adenoid hypertrophy, and sleep quality. The random forest algorithm emerged as the optimal model, achieving an AUC of 0.780 (95%CI: 0.742-0.818), accuracy of 0.793, recall of 0.793, and F1-score of 0.753 on the test set; the Brier score was 0.18, indicating good calibration of the model. SHAP analysis elucidated the contributions of specific features to the model's prediction of TD with ADHD, with learning initiative (mean |SHAP| = 0.07) and guardian type (0.05) identified as the most influential predictors, followed by academic performance (0.04), allergic rhinitis (0.03), irritability (0.03), adenoid hypertrophy (0.02), and sleep quality (0.02). These findings may provide preliminary references for future screening research and support further investigation into early identification of comorbidity, pending independent validation. However, external validation is required before any clinical implementation. This is a single-center retrospective study without external validation, and the generalization ability of the model needs to be further verified.