# Psychometric validation and determination of minimal clinically important differences for the strengths and difficulties questionnaire in adolescents with myopia

## TL;DR

This study validates the Strengths and Difficulties Questionnaire (SDQ) for assessing mental health in adolescents with myopia, determining a 2-point threshold for meaningful changes.

## Contribution

The study provides the first psychometric validation of the SDQ in adolescents with myopia and establishes a minimal clinically important difference (MCID) of 2 points.

## Key findings

- The SDQ showed acceptable internal consistency (Cronbach’s α = 0.71) and good test–retest reliability (ICC = 0.73).
- Construct validity was supported by strong correlations between problem-related subscales and difficulty scores (r = 0.51–0.72).
- The MCID for the SDQ in this population was determined to be between 2.00–2.38 points.

## Abstract

Myopic adolescents face multiple psychological challenges, including anxiety, depression, and social isolation, necessitating multidimensional assessment. One such assessment tool is the Strengths and Difficulties Questionnaire (SDQ), though it has not yet been validated in this specific population. This study aimed to evaluate the reliability, validity, responsiveness, and the minimal clinically important difference (MCID) of the SDQ in this specific population.

Following the consensus-based standards for the selection of health measurement instruments (COSMIN) guidelines, we conducted a psychometric evaluation combining cross-sectional and longitudinal designs among 307 adolescents with myopia (including newly diagnosed and follow-up cases). Baseline assessments evaluated feasibility, reliability (internal consistency and test–retest stability), and validity (construct and discriminant validity). Follow-up surveys after myopia correction were used to assess responsiveness and establish the MCID using anchor-based methods.

The SDQ demonstrated acceptable internal consistency (Cronbach’s α = 0.71) and good test–retest reliability (ICC = 0.73). Construct validity was supported by strong correlations between problem-related subscales (peer problems, hyperactivity/inattention, conduct problems, emotional problems) and difficulty scores (r = 0.51–0.72, p < 0.001), with moderate-to-strong correlations for total SDQ scores (r = 0.36–0.75, p < 0.001). Discriminant validity was confirmed by significant differences in prosocial behavior (p < 0.01). While responsiveness was modest [effect size (ES) = −0.26, standardized response mean (SRM) = −0.28], the MCID was determined to range between 2.00–2.38 points, with a threshold of 2 points recommended for group-level discrimination.

The SDQ is a reliable and valid tool for assessing psychological well-being in adolescents with myopia. The established MCID of 2 points enhances its clinical utility for screening and monitoring mental health changes in this population.