PubMed · 10479815
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L McAuley. ADHD.. https://doi.org/10.1097/00005721-199909000-00020
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In children with attention-deficit hyperactivity disorder (ADHD), motoric hyperactivity is one of the striking abnormalities. Because this symptom might be due to an insufficient motor control, motor system excitability in 18 drug-naive ADHD-children aged 8-12 years was compared to 18 age-matched healthy children using the technique of transcranial magnetic stimulation (TMS). Whereas motor thresholds, cortical silent period, and intracortical facilitation did not differ between the two groups, ADHD-children had significantly reduced intracortical inhibition compared to healthy controls. In all ADHD-children, a second TMS could be started after their first intake of 10 mg methylphenidate. Under this medication, a significant enhancement in intracortical inhibition could be stated. This study provides the first evidence for inhibitory deficits within the motor cortex in ADHD-children and for an enhancement of inhibitory mechanisms in this brain region by methylphenidate.
Attention-deficit hyperactivity disorder is a childhood psychiatric disorder characterized by inattention, impulsivity, and overactivity. Considerable research has focused on the neurobiological substrates of this disorder. Although the specific nature of the brain dysfunction remains elusive, progress has been made and several models of the underlying pathophysiology have been suggested. Research in the fields of neuropsychology, neuroimaging, neurochemistry, and molecular genetics, which points to a multifactorial etiology for the disorder, is reviewed. While several inconsistencies exist across studies, evidence supports dysfunction of fronto-striatal dopaminergic and noradrenergic circuits with resultant executive deficits in cognitive functioning.
CONTEXT: Recent reports on the use of psychotropic medications for preschool-aged children with behavioral and emotional disorders warrant further examination of trends in the type and extent of drug therapy and sociodemographic correlates. OBJECTIVES: To determine the prevalence of psychotropic medication use in preschool-aged youths and to show utilization trends across a 5-year span. DESIGN: Ambulatory care prescription records from 2 state Medicaid programs and a salaried group-model health maintenance organization (HMO) were used to perform a population-based analysis of three 1-year cross-sectional data sets (for the years 1991, 1993, and 1995). SETTING AND PARTICIPANTS: From 1991 to 1995, the number of enrollees aged 2 through 4 years in a Midwestern state Medicaid (MWM) program ranged from 146,369 to 158,060; in a mid-Atlantic state Medicaid (MAM) program, from 34,842 to 54,237; and in an HMO setting in the Northwest, from 19,107 to 19,322. MAIN OUTCOME MEASURES: Total, age-specific, and gender-specific utilization prevalences per 1000 enrollees for 3 major psychotropic drug classes (stimulants, antidepressants, and neuroleptics) and 2 leading psychotherapeutic medications (methylphenidate and clonidine); rates of increased use of these drugs from 1991 to 1995, compared across the 3 sites. RESULTS: The 1995 rank order of total prevalence in preschoolers (per 1000) in the MWM program was: stimulants (12.3), 90% of which represents methylphenidate (11.1); antidepressants (3.2); clonidine (2.3); and neuroleptics (0.9). A similar rank order was observed for the MAM program, while the HMO had nearly 3 times more clonidine than antidepressant use (1.9 vs 0.7). Sizable increases in prevalence were noted between 1991 and 1995 across the 3 sites for clonidine, stimulants, and antidepressants, while neuroleptic use increased only slightly. Methylphenidate prevalence in 2- through 4-year-olds increased at each site: MWM, 3-fold; MAM, 1.7-fold; and HMO, 3.1-fold. Decreases occurred in the relative proportions of previously dominant psychotherapeutic agents in the stimulant and antidepressant classes, while increases occurred for newer, less established agents. CONCLUSIONS: In all 3 data sources, psychotropic medications prescribed for preschoolers increased dramatically between 1991 and 1995. The predominance of medications with off-label (unlabeled) indications calls for prospective community-based, multidimensional outcome studies.