Alice Charach

The Persistence of Cognitive Deficits in Remitted and Unremitted ADHD: A Case for the State-Independence of Response Inhibition.

Background Response inhibition, working memory, and response variability are possible endophenotypes of ADHD based on their association with the disorder and evidence of heritability. One of the critical although rarely studied criteria for a valid endophenotype is that it persists despite waxing and waning of the overt manifestations of the disorder, a criterion known as state-independence. This study examined whether these aspects of cognition exhibit state-independence in ADHD. Methods One hundred and seventy-nine children diagnosed with ADHD in a rigorous baseline assessment were contacted for follow-up assessment in adolescence. Of this sample, 130 (73%) were reascertained. At follow-up, children previously diagnosed with ADHD were identified as remittent (n = 24), persistent (n = 64), or in partial remission (n = 42) based on symptoms and impairment of the disorder. Response inhibition, working memory, and response variability were assessed both in childhood (baseline) and adolescence (follow-up) and were compared with age-matched controls (40 children and 28 adolescents) seen at either time point. Results Relative to controls, ADHD children showed baseline deficits in response inhibition, working memory, and response variability. Only the group difference in response inhibition remained significant in adolescence. In general, cognitive performance among ADHD participants improved with age and did so regardless of changes in ADHD symptoms and impairment. Within the ADHD group, however, cognitive performance in childhood and in adolescence did not differ amongst those with persistent, remittent, and partially remittent forms of the disorder. Conclusions Results demonstrate that response inhibition not only distinguishes ADHD children from their unaffected peers but is also state-independent, such that deficits remain present irrespective of changes in the disease phenotype. In other words, inhibitory deficits measured in childhood persist into adolescence even when the ADHD phenotype remits. These findings provide further evidence that the ability to stop prepotent actions is an endophenotype of ADHD.

Correlates of Methylphenidate Use in Canadian Children: A Cross-Sectional Study

Objectives: This study aimed to estimate the prevalence of methylphenidate (MPH) use among Canadian children aged 2 to 11 years, from 1994–1995 to 1998–1999 and to identify sociodemographic, child, and parent–family correlates are identified. Methods: Cross-sectional data collections from the National Longitudinal Survey of Children and Youth (NLSCY) for 1994–1995, 1996–1997, and 1998–1999 were used and samples weighted up to population levels (n = 17 814 in 1994–1995, 13 575 in 1996–1997, and 18 980 in 1998–1999). Logistic regression identified correlates of parent-reported MPH use in each time period. Results: MPH use by Canadian children increased from 1.33% (95% confidence interval [CI], 1.17% to 1.50%) in 1994–1995 to 1.60% (95%CI, 1.42% to 1.78%) in 1998–1999. Use among school children aged 6 to 11 years increased from 1.94% (95%CI, 1.68% to 2.20%) in 1994–1995 to 2.42% (95%CI, 2.14% to 2.71%) in 1998–1999. Use of MPH increased among girls, from 0.52% (95%CI, 0.32% to 0.67%) in 1994–1995 to 0.97% (95%CI, 0.77% to 1.17%) in 1998–1999. For a child with parent-reported hyperactivity, the odds ratios for using MPH were 6.30 (95%CI, 4.94 to 8.90) in 1994–1995 and 12.54 (95%CI, 9.74 to 16.16) in 1998–1999. Age 6 to 11 years, male sex, and absence of parental alcohol use were significant correlates of MPH use in all time periods. Parental smoking correlated with MPH use in 1994–1995 and in 1998–1999. Conclusions: Less than 2% of Canadian children used MPH between 1994 and 1999. Some increase in use occurred among school-aged children and girls. Parent-reported hyperactivity was the most important correlate of MPH use.