Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) prenatal and postnatal risk factors and polygenetic risk scores.

Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) are neurodevelopmental disorders with onset in the developmental period. The etiology of ADHD and ASD involves both genetic and environmental factors. Most of the environmental risk factors studies have been conducted separately for each disorder, and still more genetic studies should be done to investigate the relation with the environmental factors and these disorders. The aim of this thesis is to explore environmental risk factors for ADHD and ASD and identify common risk factors between the groups. Additionally, it aims to investigate the interplay between environmental risk factors and polygenetic risk scores. For this purpose, two studies have been carried out. To investigate ADHD and ASD exposure to environmental factors a case control study was developed at the University of Cagliari, Italy, at the Unit of Child and Adolescent Neuropsychiatry at “A.Cao” Paediatric Hospital and “S. Michele” Hospital, Hospital Trust, Cagliari. The other study was carried out at the University of Groningen, The Netherlands, at the Child and Psychiatric Unit, University Medical Center Groningen, using a prospective birth cohort study “The Avon Longitudinal Study of Parents and Children (ALSPAC)” to investigate the interplay between maltreatment and different forms of maltreatment and ADHD traits. Environmental factors, such as cesarean delivery, formula feeding, high sugar consumption, family adverse situations, psychological aggression, bullying, inconsistent discipline and hostility of the mother were associated with an increased risk of ADHD. Regarding the interplay between environmental factors and polygenetic risk scores in relation to ADHD traits, a gene-environment correlation predicted maltreatment in children and a genetic liability of the parents may be involved. Gene-environment correlation (rGE) plays an important causal role in psychiatric disorders, and the identification of rGE may suggest targets for environmental intervention. These findings showed the important role of the genetic and environmental factors in neurodevelopmental disorders such as ADHD. An emphasis on environmental factors should be taken into consideration as a clinical intervention of ADHD.