High social jetlag in healthy youth: Differences in tryptophan levels, temporal pole-centered gray matter volume, and functional connectivity

Social jetlag (SJL), defined as a mismatch in midsleep timing between school or workdays and free days, has been associated with adverse mental health, cognitive, and brain outcomes in adults. However, its effects in young individuals remain insufficiently studied. We investigated the effects of SJL on these factors and on tryptophan metabolites, an amino acid implicated in sleep, fatigue, and social function, in young individuals. Based on SJL assessed using the Munich Chronotype Questionnaire, 89 healthy youths aged 6–17 years were classified into a high-SJL group (≥ 1 h; n = 25) or a low-SJL group (< 1 h; n = 64). Fatigue, chronotype, Trail Making Test (TMT) performance, urinary tryptophan and 5-hydroxyindoleacetic acid (5-HIAA) levels, gray matter volume (GMV), and resting-state functional connectivity (FC) were evaluated. Compared with the low-SJL group, the high-SJL group exhibited greater fatigue, a later chronotype, and higher urinary tryptophan levels. Moreover, the high-SJL group showed smaller GMV in several regions, including the temporal pole. Notably, the left temporal pole, a region implicated in socioemotional processing, showed reduced FC with the right pars triangularis in the high-SJL group. However, TMT performance and urinary 5-HIAA levels did not differ between groups. An SJL of ≥ 1 h was associated with temporal pole-centered neural vulnerability and elevated tryptophan levels in young individuals. These findings suggest that higher SJL may contribute to neural and molecular disadvantages related to socioemotional functioning during childhood and adolescence.