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Aim: Psychotropic medication can contribute to arrhythmia and identifying individuals at risk is crucial. This Swedish study compared the corrected QT (QTc) intervals of adolescents on psychotropic medication with unmedicated controls, when supine and after rising rapidly.

Methods: The study was carried out at Östersund County Hospital in March 2022 and February to March 2023. It comprised 16 cases, aged 10–17 years and 28 controls. QTc intervals were measured with electrocardiography and calculated using Bazett's and Fridericia's formulas. Univariate and multiple linear regressions were used to assess differences in QTc intervals between the cases and controls and across sex, age and body mass index.

Results: The mean QTc interval when supine, calculated with Bazett's formula, was longer for the adolescents on psychotropic medication than the controls (p = 0.046). The same was true for the mean QTc interval after rising rapidly from the supine position, calculated with both Bazett's formula (p = 0.009) and Fridericia's formula (p = 0.007). Mean QTc intervals varied by sex and age groups. Psychotropic medication prolonged QTc intervals, particularly in girls.

Conclusion: Longer QTc intervals were found in adolescents on psychotropic medication, particularly after rising rapidly from the supine position.