Mild-to-moderate iodine deficiency and symptoms of emotional distress and depression in pregnancy and six months postpartum - Results from a large pregnancy cohort.

Background: The relationship between iodine intake and depression is unknown. The aim of the present study was to investigate whether iodine intake was associated with symptoms of perinatal emotional distress and depression in a mild- to moderately iodine deficient population.
Methods: The study population comprised 67,812 women with 77,927 pregnancies participating in the Norwegian Mother, Father and Child Cohort Study. Self-reported emotional distress and depressive symptoms were reported in pregnancy and at six months postpartum. Iodine intake was assessed by a food frequency questionnaire in mid-pregnancy. Urinary iodine concentration (UIC) was available for 2792 pregnancies.
Results: The median iodine intake from food was 121 μg/day and the median UIC was 68 μg/L. The prevalence of high scores for emotional distress was 6.6 % in pregnancy and 5.8 % six months postpartum, and for high scores on postpartum depression it was 10.3 %. In non-users of iodine supplements (63 %), a low maternal iodine intake from food (lower than ~100-150 μg/day) was associated with increased risk of high scores of emotional distress and depression both in pregnancy and six months postpartum (p < 0.001). Iodine supplement use was associated with increased risk of high scores of emotional distress in pregnancy compared to no supplement use or use of supplements without iodine.
Limitations: Observational design, self-report information, and short scales to assess symptoms of emotional distress and depression.
Conclusion: A low habitual iodine intake was associated with increased prevalence of perinatal emotional distress and depression. The potential non-beneficial effect of iodine supplements may have biological explanations. More studies are needed.
Competing Interests: Conflict of Interest M.H.A. was until Dec. 2019 employed by the Norwegian dairy company TINE SA, and she participated in this project as an industrial Ph.D.-student financed partly by TINE SA and partly by The Research Council of Norway. This project is designed, owned, and administered by The Norwegian Institute of Public Health (NIPH) and analysis of the data follow from protocol. All results of analysis in the project are to be published regardless of the results. TINE SA supported the project to raise awareness on the importance of iodine and to gain more knowledge about the potential health effects of milk in the Norwegian diet. Today, M.H.A. is a full-time researcher at the NIPH. The other authors declare that they have no competing interests.
(Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)