Attention Deficit Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder that affects a number of brain functions. Although there are no known causes, several factors may contribute to this disorder. Such factors may include genetics, exposure of fetus to tobacco, alcohol or other drugs, illnesses or a history of a head injury. The general core characteristics are impulsive behaviour, hyperactivity and inattention, which ultimately interferes with one’s ability to appropriately control their behaviour and cognition. It is a highly prevalent disorder in childhood, in which most symptoms may persist into adulthood, resulting in poor academic and social outcomes (Rubia, 2018). ADHD is associated with possible functional impairment, as well as significant social and medical implications in children and adults. Children with ADHD often exhibit working memory difficulties along with executive function problems that include response inhibition, attentional switching, planning and sustained attention (Holmes et al., 2014). It is therefore essential to consider all aspects of a child’s disorder and life, in order to develop an approach to effectively treat them (Wilens & Spencer, 2010).
A multimodal approach that combines medication with behavioural management, psychological counselling and family support is essential for an effective treatment (Martinez-Raga, Ferreros, Knecht, de Alvaro, & Carabal, 2017). However, implementing stimulant medications is considered a widely used treatment for children with ADHD (Gold, Blum, Oscar-Berman, & Braverman, 2014). It also plays a significant role in the long-term management and treatment of children with ADHD (Wilens & Spencer, 2010). Stimulants can be effective in improving symptoms, additionally leading to possible favourable outcomes such as improved academic or work performance, or reduced criminality. There is some evidence that the use of medication can reduce the risk of criminality among patients with ADHD (Lichtenstein et al., 2012) and is therefore, effective in relieving symptoms. In addition, medications are considered cost-effective in comparison with a combination of medications and behavioural treatment (Wu et al., 2012). However, there are side effects and risks associated with this treatment and is therefore considered a debatable treatment, which often requires a comprehensive evaluation and consideration during usage. Stimulant medications are therefore an effective treatment with a well-established efficacy, but is associated with potential risks and side effects (Martinez-Raga et al., 2017).
Stimulants are the most widespread medications approved by the Food and Drug Administration (FDA) (De Sousa & Kalra, 2012) and is associated with potential risks and adverse effects, which prompts people to investigate its’ effectiveness in treating children. Stimulant medications, including amphetamine and methylphenidate can have a paradoxical effect on children with ADHD, by calming and possibly improving both their cognitive and non-cognitive symptoms. The release of stimulants in the pre-frontal cortex can subsequently increase the levels of dopamine, which are neurotransmitters that regulates emotional responses such as attention and pleasure (De Sousa & Kalra, 2012). However, the specific mechanisms of these stimulants may differ, in which some stimulants may either increase dopamine by blocking the presynaptic dopamine transporter or may stimulate the release of vesicular dopamine stores in the presynaptic terminals (Bidwell, McClernon, & Kollins, 2011), using the dopamine transporter as a carrier (Lakhan & Kirchgessner, 2012). As children with ADHD exhibits lower levels of dopamine, this is an effective method of gradually increasing its’ levels and in turn, regulate the child’s motivation, attention and memory formation. Although stimulants are associated with an exceptional response rate, some children with ADHD may exhibit a poor toleration or a lack of response to this treatment (Martinez-Raga et al., 2017). Therefore, the effectiveness of stimulant medications can vary depending on the individual with ADHD.
Stimulant medications may effectively treat or improve attention deficit in individuals with ADHD. In particular, methylphenidate can significantly increase dopamine levels in the ventral striatum, a region of the brain associated with decision making and reward-related behaviours (Lakhan & Kirchgessner, 2012). Moreover, this increase in the ventral striatum may enhance the saliency of the task and thus, improve attention in ADHD (Lakhan & Kirchgessner, 2012). Although stimulants may improve sustained, focused attention, selective attention and distractibility may worsen due to an increase in impulsivity (Lakhan & Kirchgessner, 2012). As children with ADHD exhibit decreased activity in ventral striatum during reward anticipation (van Hulst et al., 2017), stimulant medications will therefore improve those cognitive deficits. Particularly, in the medial prefrontal cortex, impaired reward anticipation behaviours often correlates with impaired decision making and learning in children with ADHD (Hauser et al., 2014). However, there are minimal evidence that supports the effectiveness of stimulant medications on decision-making, with some suggesting that stimulants do not ameliorate the decision-making deficits (DeVito et al., 2008). In addition to this, many studies still fail to indicate that stimulant medications can alter a child’s academic performance or learning (Neef, Bicard, Endo, Coury, & Aman, 2005). However, according to Felt’s study, it may improve their learning and academic perfomrnace, as they are less likely to be held back a grade (Felt, Biermann, Christner, Kochhar, & Harrison, 2014). Therefore, its effectiveness in treating children with ADHD remains controversial and thus, further research is required.
Similarly, the release of stimulants may also boost the levels of norepinephrine, which is a neurotransmitter related to arousal and attentiveness. A release of stimulant, methylphenidate will inhibit norepinephrine transporters, which reuptake norepinephrine and thereby, increase the catecholamines levels (Rubia et al., 2014). Therefore, increasing norepinephrine activity, which impacts on executive and attentional function (Faraone, 2018). Norepinephrine can alter the network activity in the higher-order processing areas of attention and working memory and by increasing its’ levels, modulate sustained attention and increase frontoparietal network activation (O’Donnell, Zeppenfeld, McConnell, Pena, & Nedergaard, 2012). Stimulants are therefore effective in treating the cognitive deficits in children with ADHD by increasing levels of dopamine and norepinephrine activity.
There are beneficial effects associated with the use of stimulant medications on working memory performance in children with ADHD. Stimulant medications can help strengthen and enhance the functional connectivity of some frontoparietal brain regions that are engaged for working memory (Wong & Stevens, 2012). Such enhancement is achieved through better coordination of information processing across the specialised nodes of connected networks. Therefore, activating the network engagement, as well as changing the regional functional connectivity. Evidence has shown that an increased activation of regional functional connectivity in the frontoparietal regions was correlated with improved working memory performance (Burgess et al., as cited in Wong & Stevens, 2012). In particular, the ability to store and manipulate visual-spatial information is improved but with no beneficial effects on the storage of auditory-verbal information (Bedard, Jain, Johnson, & Tannock, 2007). Therefore, the effects of stimulants are selective, as it will vary depending on the working memory component or task used. However, it is ultimately recommended to have a synergistic approach for treating children with ADHD to achieve optimal results (Holmes et al., 2014).
As there are structural abnormalities in the basal ganglia of children with ADHD, it is therefore important to investigate the effectiveness of stimulant medications in treating those associated cognitive deficits. Children with ADHD often have changes or a reduction in grey matter, which can be modulated by medication (Ellison-Wright, Ellison-Wright, & Bullmore, 2008). They present with abnormal volume and cortical thickness in the corpus callosum, prefrontal regions, basal ganglia and the temporal and parietal cortices (Nakao, Radua, Rubia, & Mataix-Cols, 2011). Possible expansion of the gray matter volumes and cortical thickness can be associated with the use of stimulant medications on ADHD, which has a normalizing effect on the brain structure (Nakao et al., 2011; Sobel et al., 2010). As medications are known to block dopamine transporters in the basal ganglia, it can enhance and normalize the activation in the basal ganglia (Rubia K, as cited in Nakao et al., 2011) and thereby, repair abnormal basal ganglia structure and elicit morphological changes in children with ADHD. It is further emphasised that medicated patients experience an increase in normal brain structure in comparison with unmedicated patients of ADHD. However, there are inconsistent evidences supporting this, which suggests that further research is required to investigate the changes in brain or basal ganglia volume (Nakao et al., 2011).
As children with ADHD often demonstrate executive function difficulties, one must evaluate the effectiveness of stimulant medication in treating those cognitive deficits. There is an absence of consistent evidence that stimulant medications enhance or alleviate executive function deficits (Bidwell et al., 2011). Therefore, its effectiveness in treatment is still undetermined. Stimulants, however, have varying effects depending on the dose and the domain of function, with high doses producing a greater improvement on some (e.g. attention, memory, working memory) but not others (e.g. planning, cognitive flexibility) (Bidwell et al., 2011). However, a randomised clinical trial has concluded that stimulants do not moderate or consistently improve those executive function deficits (Biederman et al., 2011). Therefore, additional intervention alternatives for executive function should be further explored, in which stimulant medications are used in conjunction with other strategies/management.
Stimulant medications, however, have both benefits and harms on behavioural effects which has elicited much discussion and concerns. Using stimulants without a prescription or using frequent doses of stimulants than prescribed, has been a prevalent and growing problem among populations of children transitioning to adolescents (Martinez-Raga et al., 2017). There are persistent concerns with the increased risk of substance abuse among individuals prescribed with stimulant ADHD medications. There are no indications of increased risk of substance abuse but instead, suggestions of long-term protective effect on substance abuse (Chang et al., 2014). However, evidences have also suggested that there is a dramatic increase in the misuse of stimulants by ADHD individuals, which may be a result of misconceptions (Lakhan & Kirchgessner, 2012). Moreover, stimulants may reduce emotional reactions to frustration and increase effortful behaviour. Although stimulants may or may not provoke substance abuse, it is essential to remain alert to the potential problem of stimulant misuse in children with ADHD (Chang et al., 2014). On the contrary, possible promotion of “risky behaviour”, as well as an increased susceptibility to environmental distractions can be a result of using these drugs (Advokat & Scheithauer, 2013). Other potential behavioural effects may include mood changes, anxiety and depression. Due to these “psychological side effects”, treatment discontinuation is considered significantly high in children (Advokat & Scheithauer, 2013). Therefore, despite its effectiveness in reducing symptoms, patients will often discontinue the use of stimulant medications. Aside from these side effects, inappropriate use could harm children by stigmatising them or by preventing possible advantageous treatments (Currie, Stabile, & Jones, 2014). Furthermore, long-term benefits of stimulant medications in treating children with ADHD remains controversial (Currie et al., 2014). Such stimulants are often prescribed to potentially improve a child’s academic performance to be successful in school. As there is little evidence associated with this, subjecting children to stimulant medications with potential side effects is weakened (Currie et al., 2014). Therefore, prompting one to debate about the moral implications of using drugs to effectively treat children with ADHD.
It is essential for further research on the effectiveness of stimulants, as there are several limitations to each evidence. One inherent limitation is that the peak-based meta-analyses are generally based on summarised rather than raw statistical brain maps and as a result, produce less accurate results (Nakao et al., 2011). Each study included in this essay used different statistical thresholds which can still be statically correct (Nakao et al., 2011). However, it is still unknown whether these differences can affect the validity of those researches. Furthermore, often the results for substance abuse are interpreted through the medical and legal records of substance-related hospitalisations, deaths and convictions, which are mainly severe cases of drug abuse (Chang et al., 2014). Therefore, further research is required to investigate whether these findings generalize to less severe cases. According to Van Hulst, his study involved primarily boys to preserve statistical power and therefore, will only apply to boys with ADHD. Moreover, the reward tasks were designed to detect differences in anticipatory activity rather than reward processing and as a result of collinearity, the brain activity could not be analysed separately (van Hulst et al., 2017).
Ultimately, future research is required to investigate the effectiveness of stimulant medications in treating children with ADHD. It is however, recommended to implement a multimodal approach, in which medications are combined with behavioural therapy and family support to effectively treat children with ADHD. In addition to this, early intervention is ideal, as it may reduce the negative outcomes associated with ADHD (Dopheide & Pliszka, 2009). Generally, there are benefits and harms associated with the use of stimulant medications and such controversies may include possibility of substance abuse, “risky” behaviour and inconsistent improvement of those executive function deficits. On the contrary, stimulant medications may modulate and alter working memory function, sustained attention and planning by increasing the dopamine and norepinephrine levels and enhancing the functional connectivity in the frontoparietal regions of the basal ganglia and ventral striatum.