The impacts of iron deficiency on mental health in childhood

Numerous studies have found associations between iron deficiency (ID) and iron deficiency anemia (IDA) and poor cognitive and motor development in infancy and early childhood. In addition, it has been reported that there are associations between ID/IDA and some childhood neuropsychiatric disorders including attention deficit hyperactivity disorder, conduct disorders, autism spectrum disorders, restless leg syndrome, sleep disturbance and Tourette's syndrome. Iron is required for proper function of some enzymes that are engaged in the myelinization process and in monoamine neurotransmitter synthesis. Therefore, it has been considered that these negative effects of ID and IDA are related to the vital roles of iron in the brain. Thus, authors have suggested that the presence of ID without anemia is sufficient for occurrence of functional disturbances, although exceptions exist. There are studies which considered that, especially early in life, the negative impacts of ID on psychomotor and neurological development do not seem to be reversible by iron supplementation and ID may cause permanent hazards in the brain. However, some studies have reported that iron supplementation resolved the effects of ID including cognitive and motor development problems in children and the development of psychiatric disorders. Despite there being large amounts of data, the possible confounding effects of poor socioeconomic backgrounds prevent causal inferences. Even nowadays, it is still not clear whether poor development of iron-deficient children is related to poor social backgrounds or irreversible damage due to ID and if it is remediable with iron treatment.