performance, 20, 22 occupational performance, 20 family relationships, 20 intimate relationships, 20 social relationships, 20, 22 psychological wellbeing, 20 self-perception, 20 self-worth or self-esteem, 20 capacity to perform daily living tasks, 20 and engagement in recreational activities. 20
Changes in motivation and reinforcement processing, which may contribute to certain symptoms of emotional dysregulation, have also been observed in individuals with ADHD. 6 Children diagnosed with ADHD frequently prefer immediate rewards over delayed ones and tend to show reduced sensitivity to reinforcement, and their reaction to a reward may diminish more quickly than that of their unaffected counterparts. 6 Children diagnosed with ADHD often experience considerable deficiencies in both learning and social abilities, potentially leading to longlasting difficulties in personality growth and development, communication with others, and adaptation to social environments. 2
Risk factors of ADHD
ADHD is a dynamic, complex, and multidimensional condition, with multifactorial causes. ADHD is rarely caused by a single genetic or environmental risk factor; instead, most cases result from the combined and cumulative effect of multiple genetic and environmental influences, each playing its part, 1 like the pieces of a puzzle. After reviewing the literature, many risk factors for ADHD have been identified. This section focuses on the following risk factors: genetics, 6 thyroid dysfunction, 7 physical trauma, 8 asthma, 9 microbiome, 5 gut-brain axis, lead exposure, 10, 11 tobacco smoke, 12-14 alcohol, 14, 15 preterm birth, 16 family adversity, 17 and exposure to organochlorines, 18 polychlorinated biphenyls, 10, 11 mercury, 10 and
10, 19 organophosphate pesticides.
Genetics and ADHD
ADHD has a strong genetic component. Research involving twins, families, and adopted children or siblings shows that inheritability of ADHD ranges from 60 % to 90 %. 6 Family studies have consistently revealed that the rates of ADHD are significantly higher( ranging from twofold to eightfold increased risk) in parents and siblings of affected individuals than those of relatives of unaffected individuals. Additionally, twin studies indicate that monozygotic twin pairs exhibit considerably greater concordance rates for ADHD than their dizygotic counterparts. 25 Furthermore, adoption studies have demonstrated elevated rates of ADHD among the biological parents of adoptees with ADHD, compared to both the adoptive parents of these individuals and the parents of those without ADHD. 25 Genes can influence sensitivity to environmental risks( gene-environment interaction). 25
Thyroid dysfunction and ADHD
Maternal thyroid dysfunction may damage foetal brain development. 26 Research shows a link between maternal hypothyroidism and the likelihood of ADHD in children. 7 A comprehensive nationwide cohort study included 1,260 children under the age of 12 years with a confirmed diagnosis of congenital hypothyroidism and no previous diagnosis of any neurodevelopmental disorders. The findings revealed that children diagnosed with congenital hypothyroidism exhibited nearly a two-fold increased risk of ADHD. 7 A population-based cohort study examined 857,014 singletons who were alive and living in Denmark at the age of 3 years. 27 Among these, 30,295 singletons( 3.5 %) were born to mothers experiencing thyroid dysfunction. The diagnosis and treatment of maternal hyperthyroidism for the first time after the child’ s birth showed an increased risk of ADHD in the child( adjusted HR 1.23; 95 % CI 1.05-1.44). Children whose mothers were diagnosed and treated for thyroid dysfunction for the first time post-birth may have been subjected to abnormal levels of maternal thyroid hormone that were already present during pregnancy. 27 A case-cohort study was conducted within the Danish National Birth Cohort( 1997-2003). The prevalence of abnormal maternal thyroid function in the sub-cohort was 12.5 %. In girls, isolated low free thyroxine levels were linked to ADHD( aHR = 2.3 [ CI 1.2-4.3 ]), whereas no association was observed in boys. 26
Physical trauma and ADHD
The combination of high levels of physical activity, impulsivity, and inattention increases the risk of falls and other accidents. 8 Additionally, children diagnosed with ADHD often act without sufficient awareness or consideration of their surroundings, which makes them more susceptible to unintentional injuries and traumas than in the general population. 8 A research study investigated the prevalence of ADHD symptoms and the related risk factors among children( aged 3-16 years) who were admitted to the Emergency Department as a result of trauma. 8 The trauma patients were categorised into two groups: those who had been diagnosed with ADHD and those who had not. The factors that heightened the risk of ADHD included admission due to extremity traumas( P < 0.001), prior Emergency Department admissions for traumas( P < 0.001), and having a
206 | vol31 | no4 | AJNM