ADHD
Describe Deficit
Attention Deficit Hyperactivity Disorder (ADHD) is a developmental disorder with early onset in childhood and extends to adulthood in about 60% of the patients (Chandan, 2012). Several motivational and cognitive processes are implicated in the age-inappropriate impulsivity, hyperactivity, and inattention symptoms characteristic of ADHD. Defects in the cognitive domain include working memory, a multicomponent function with roles in short-term and real-time information manipulation and storage, which is essential for the maintenance of goal-oriented behavior, decision-making, and learning. There are robust working memory deficits in pediatric individuals with ADHD especially in the processing of visual-spatial information: these require executive control. The motivational domain, on the other hand, includes reinforcement, reward, and motivation aspects. ADHD is particularly associated with a steeper gradient of reinforcement, overall disregard of delayed consequences, and dysfunction in reward thresholds.
ADHD symptoms appear before 12 years of age and cause marked dysfunction in various setting such as with social interactions with peers and family members and in terms of learning difficulties in school (Theresa et al, 2018).
Brain Structures and Circuits affected
The atypical or delayed prefrontal cortex maturation which mediates the control functions affects developmental course in children suffering from ADHD, thus producing inappropriate impulsivity, inattention, and hyperactivity levels for age (Chandan, 2012). Cerebral Imaging modalities reveal cerebral volumetric reductions; that the overall cerebellar and cerebral volumes together with the lobar white and gray matter volumes are decreased by about 4 % in ADHD patients. Multimodal cortices form focal centers of volume reduction, they include the basal ganglia, premotor cortex, medial and anterior temporal lobes, frontal lobes, posterior cingulate, and the lobules of the cerebellum. Children with ADHD typically have a thinner cortical mantle; peak thickness is first attained in the sensory cortices and later in the association cortices like in the normal children, however, the age of achievement of peak thickness differs with ADHD patients attaining it later; between age 10-11; normal children attain the peak thickness between age 7 and 8.
The developmental alterations in the cortical mantles of the frontal cortex and caudate nucleus regions are particularly important in ADHD; the caudate and frontal cortex form a neural circuit, important in executive control of behavior. ADHD symptoms exhibit dysfunction in executive brain functions particularly working memory, suppression of interference, and response inhibition, which are important in the regulation of goal-oriented behavior and attention. The main circuitry involved comprises; the frontal cortex regions (anterior cingulate, premotor, and prefrontal cortices), the cerebellum, and dorsal striatal regions connected via the projections of the thalamus. ADHD children showed reduced activation of the Stop and the Go/No-go response inhibition signals, inferolateral frontal inhibition areas, anterior dorsal cingulate responsible for inhibitory functions, and reduced activation of multiple areas of the frontal cortex involved in working memory. The children also show hyperactivation of the anterior cingulate and inferior frontal cortices during inhibitory regulation.
With regards to reward and motivation controlled by the dopaminergic mesolimbic projections, ADH children and adolescents show lesser activation of the orbitofrontal cortex, the hippocampus, and ventral striatum in the anticipation of reward (motivation).
Assessments
According to the American Psychiatric Association, the diagnostic criteria for ADHD requires an early onset of impulsivity and/or inattention symptoms (before 7 years of age) and their expression in not less than two instances in the previous 6 months. The majority of ADHD diagnostic guidelines recommend a combination of various methods such as clinical ratings and tests, observations, and interviews. The DSM V (Diagnostic and Statistical Manual of Mental Disorders) categorized ADHD into 3 main categories; the Inattentive (IA) type, the hyperactive (HI) type, and the combined (C) hyperactive and inattentive type. The primarily HI type more than 6 relevant HI symptoms and less than 6 of the relevant IA symptoms while the primarily IA type more than 6 relevant IA symptoms and less than 6 of the relevant HI symptoms. The C type sore greater than 6 relevant symptoms of both IA and HI types.
Clinical ratings use standardized tools to assess the typical individual performance under normal conditions while tests assess for optimal performance in controlled environments with negated outlier influences. Objective measures used in the assessment of ADHD patients include TAP (Test Battery of Attention) and the QbTest (Quantified Behavior Test). The TAP neuropsychological test (for adults and adolescents) and the KiTAP variant (for children 6 to 11 years old) assess for two ADHD core aspects; impulsivity and inattention. The QbTest for children 6 to 12 years and its variant, the Qb+ for adults and adolescents is a computerized test that utilizes a consecutive performance analysis to evaluate all the three core ADHD symptoms. The QB test is preferred in diagnostic processes due to its high specificity and sensitivity- 83% and 86% respectively: TAP has a weak specificity (Theresa et al, 2018).
Interventions
Several approaches are used for the management of ADHD; they include pharmacological, non-pharmacological, and other interventions. Pharmacological interventions include stimulants such as Methylphenidate and non-stimulants such as Atomoxetine and Clonidine: these have proven short term effectiveness in reducing ADHD symptoms but are limited by limited long-term effectiveness, numerous side effects and subclinical effects in some patients. Non-pharmacologic interventions include CBT (cognitive behavioral therapy) and cognitive training, parent training strategies to enable easy coping and home-based behavioral training of the children, and environmental remodeling such as the introduction of daily routine and structure. Other measures used in ADHD include neurofeedback, exercise, and diet, nutritional supplements such as the Omega fatty acids, and the elimination and exclusion of some foods. These various intervention groups are combined based on the diagnosis, clinical preference of the physician, individual patient characteristics such as the presence of cardiac disease, availability of financial resources, and observed effectiveness (Shar, Grover & Avasthi, 2019).