Attention-deficit/hyperactivity disorder (ADHD) and learning disability (LD) can co-occur for a significant minority of children with each disorder. A total of 17 studies (2001-2011) examining ADHD-LD comorbidity were reviewed, revealing a higher mean comorbidity rate (45.1%) than has been obtained previously. Higher comorbidity may be the result of including students with writing disorders, not just reading and/or math disabilities. Proposed DSM-5 criteria for both disorders will likely affect comorbidity rates; however, it is unclear whether such rates will increase or decrease. Regardless of the specific impact of DSM revisions, academic skill and/or performance deficits should be assessed for students with ADHD as part of screening, comprehensive evaluation, and treatment monitoring. Comprehensive intervention services for students with comorbid ADHD and LD will require empirically supported treatment strategies that address both disorders and that are implemented across school and home settings.

Although, collectively, results of earlier direct observation studies suggest momentary time sampling (MTS) may offer certain technical advantages over whole-interval (WIR) and partial-interval (PIR) recording, no study has compared these methods for measuring engagement in young children in naturalistic environments. This study compared direct observations of child engagement using WIR, PIR, and MTS methods to continuous duration recording (CDR), using measurement error, correlations, and inter-observer agreement. Results indicated that MTS consistently demonstrated measurements closer to CDR compared with PIR and WIR, although in this study, the differences between MTS and PIR across indicators were not as great as has been demonstrated in the literature. WIR, PIR, and MTS were all strongly correlated with CDR, although there were issues with under and overestimations. Finally, the four observational methods were all moderately to strongly correlated with expert ratings of engagement, although none was significantly correlated with teacher rankings of classroom engagement.

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Epigenetics is the field of research that examines alterations in gene expression caused by mechanisms other than changes in DNA sequence. ADHD is highly heritable; however, epigenetics are considered relevant in potentially explaining the variance not accounted for by genetic influence. In this chapter, some of the well-known processes of epigenetics, such as chromosome organization, DNA methylation, and effects of transcriptional factors are reviewed along with studies examining the role of these processes in the pathophysiology of ADHD. Potential epigenetic factors conferring risk for ADHD at various developmental stages, such as alcohol, tobacco, toxins, medications, and psychosocial stressor are discussed. Animal studies investigating ADHD medications and changes in CNS Gene/Protein Expression are also explored since they provide insight into the neuronal pathways involved in ADHD pathophysiology. The current limited data suggest that identification of the epigenetic processes involved in ADHD is extremely important and may lead to potential interventions that may be applied to modify the expression of deleterious, as well as protective, genes.

The methylphenidate transdermal system (MTS) provides a novel method of delivery for methylphenidate, a well-studied and effective medication for attention-deficit/hyperactivity disorder. The MTS achieves two major goals. First, the delivery system allows for administration throughout the day with a single patch, thus improving adherence. Second, it is the first approved attention-deficit/hyperactivity disorder medication that is not administered orally, thus bypassing gastrointestinal absorption and first-pass metabolism through the enteric circulation. In this article, we review the current data on MTS, including preclinical, clinical and post-marketing studies, and compare efficacy and tolerability to currently available treatments.