Vitamin D deficiency (Vt.D) is common in adolescents and is influenced by some factors, including puberty. It impacted serotonin levels, thus increasing the risk of depression. This study was conducted to assess the association between vitamin D deficiency and depression and its effect on adolescent students. A cross-sectional study of 130 adolescent students aged 12-18 years, between November 2023 to February 2024. This study investigated serum Vt.D, serotonin levels, and hematological indices such as (RBC, Hb, MCV, and MCH, of adolescents, in addition, it was dependent on the Beck Depression Inventory to calculate scales of depression. 130 adolescent students were enrolled aged 12-18, mean ± SD: 14.85±2.19. The results indicated that 77(59.2%) students had depression symptoms, median (IQR) of scores16(13₋21.5), and 53(40.8%) adolescents with non-depressed (scores 5(2.5₋7), who were considered as the control group, a statistically significant between these groups (p=0.035). Depression was significantly more prevalent in females 46(59.7%) than males 31(40.3%), p=0.014. Deficiency Vt.D was found in 63.6% of the total depressive adolescents and was significantly more than nondepressive adolescents 3.8%, p<0.0001, with (B: 3.199, OR: 24.5, 95%CI: 5.96 -100.74). Serum Vt.D level was significantly decreased in depressive adolescent median (IQR) 18.8(13.1 ₋28.9) ng/ml, compared with non-depressed 52.22(42.2₋62.4), (p< 0.0001), and its lowest in a type of severe depression 10.74±3.52. The depressive adolescent group had significantly lower serotonin levels in deficiency Vt.D status than non-depressive groups (143.39±60.91 vs. 314.05±46.11), p = 0.001). Correlations and linear regression analysis to predict the risk factors for depression scores showed a significant negative correlation with levels of Vt.D (r=0.786, B: -0.109, 95%CI: -0.15 to -0.065, p<0.0001), and serotonin (r=0.848, B: 0.003, 95%CI: -0.032 to -0.019, p<0.0001), respectively. Deficiency Vt.D is an important risk factor for adolescents, especially in females, and is associated with an increased risk of depression in adolescent students
انتصار رزاق محمد شربة | Intisar M. Razzaq Sharba | 518