Pre-, Peri-, and Post-Natal Risk Factors in ADHD

Introduction

Attention Deficit/ Hyperactivity Disorder (ADHD) is the most common neurodevelopmental disorder which manifests in early childhood and persists mostly into adolescence and adulthood (Sagiv et al, 2013). It is characterized by its core symptoms of inattention, impulsiveness and hyperactivity and accessory symptoms such as disorganization, affect control, hot temper and affective liability (Tole et al, 2019; Zappitelli, Pinto and Grizenko, 2001). Children with ADHD show considerable variation in their symptom severity, degree of impairment and presence of other co-morbid conditions (Linnet et al, 2003). Prevalence varies from 5% to 10% in children (Sagiv et al, 2013) and approximately 3% in adulthood (Tole et al, 2019) with more inattentiveness exhibited and less of hyperactivity and impulsivity. ADHD generates a substantial burden on the quality of life and psychosocial functioning of affected children and their family members along with a considerable strain on medical, educational and social resources and therefore, high priority is given to study and investigate the risk factors associated with it(Tole et al, 2019; Sagiv et al, 2013).

The etiology of ADHD is multifaceted with an interplay of gene, development and environmental factors (Sagiv et al, 2013). Heritability has been considered as the strongest factor in the development of ADHD with genetic factors responsible for approximately three-quarters of the variability found in ADHD; that is, up to 75%-80% of symptoms seen in ADHD individuals are due to genetic component (Mill and Petronis, 2008; Grizenko et al, 2008). First-degree relatives of the affected person have a 2 to 8-fold risk for developing this disorder (Grizenko et al, 2008). The remaining were due to environmental factors which includes several pre-, peri- and postnatal risk factors. Previous literature has shown that insults that transpires during critical pre- and perinatal period of development tend to have a direct effect on the fetal brain leading to neurochemical alterations that are commonly associated with ADHD and other psychiatric conditions (Zappitelli, Pinto and Grizenko, 2001). As per the programming hypothesis, unfavorable intrauterine environment increases the susceptibility to disorders in later life (Linnet et al, 2003). However, research on various influences that may predispose to neonatal brain trauma in the etiology of ADHD has come out to be controversial (Zappitelli, Pinto and Grizenko, 2001).