Twin study on heritability of activity, attention, and impulsivity as assessed by objective measures.

OBJECTIVE: The purpose of this study was to assess heritability of activity, attention, and impulsivity by comparing young monozygotic (MZ) twins with dizygotic (DZ) twins using objective measures. METHOD: The OPTAx test is an infrared motion analysis to record the movement pattern during a continuous performance test. Seventeen MZ and 12 same sexed DZ twin pairs in the range of 6 to 12 years were tested. The zygosity was determined by DNA-fingerprinting. The measures under investigation were activity (microevents and spatial scaling), impulsivity (errors of commission), and attention (accuracy and variability). For statistical analyses, the classical model of Falconer and the ACE and ADE genetic model for twin data were applied in order to estimate the proportion of the variance in activity, impulsivity and attention that is due to genetic effects. RESULTS: The respective coefficients of intraclass correlations in MZ twins ranged between .35 and .65 whereas for DZ twins the correlations were between .12 and .88. The heritability estimates resulting from both models were about 30% for 4 of the 5 measures, but none of these was significantly different from 0. CONCLUSION: We found no significant influence of genetic factors for activity, attention, and impulsivity. The authors conclude that further investigation of heritability of ADHD is necessary using larger sample sizes and objective measures.

Olanzapine overdose in children and adolescents: two case reports and a review of the literature.

Although the atypical antipsychotic olanzapine is increasingly being used in child and adolescent psychiatry, reports of olanzapine overdose in this young population are scarce. We report on two cases of adolescents who attempted suicide with an overdose of olanzapine: (1) A 14-year-old female ingested 275 mg olanzapine, which produced the highest reported nonlethal serum level (1503 ng/mL) and caused somnolence, agitation (acutely), and extrapyramidal symptoms (EPS; after 54 hours) but no major clinical complications. The serum olanzapine level dropped to 129 ng/mL within 48 hours; and (2) a 17-year-old male ingested 400 mg olanzapine, the highest reported nonlethal dose of olanzapine in adolescents, which produced respiratory suppression requiring intubation and mechanical ventilation; he recovered after 3 days. Based on clinical monitoring and postmortem data, the 2 patients survived the ingestion of high doses of olanzapine. We also provide a review of the literature, encompassing all reported cases of olanzapine overdose in children and adolescents and discuss symptoms, diagnosis, and treatment options, based on pharmacokinetic and pharmacodynamic considerations.