Brain maturation, cognitive tasks, and quantitative electroencephalography : A study in children with attention deficit hyperactive disorder

Sammanfattning: Attention Deficit Hyperactivity Disorder (ADHD) is one of the most common psychiatric disorders of childhood. Despite a long history, widespread clinical acceptance, and extensive research, the diagnosis and treatment are still controversial. The aim of the thesis was to study the hypothesis that some children with ADHD may show these symptoms due to a slow speed of mental maturation with the possibility of a catch-up. · In Study I, the association between ADHD and global maturity was tested using a twin design (incl. 1106 pairs of the 1480 pairs of twins born in Sweden Apr. 1985 - Dec. 1986). The results showed different pathways through which genetic effects may influence the behavior pattern in children with ADHD. Among boys, there are at least two different genetic pathways to explain ADHD, one through predisposition for maturational lag and one specific to ADHD. A different pathway may explain ADHD in girls. · In Study II, the relationship between behavior, ADM symptoms and maturity was studied among 1079 pairs of twins from study I using a questionnaire (a global maturity parent's scale) given to the parents. Relationships were found between the maturity factor and the CBCL grouping of syndromes (internalizing, externalizing, total behavior problems score) as well as between the maturity factor and ADHD. From the parents' point of view the behavior problems in their children may be related to maturity. · In Study III, a computerized tool, the Gordon Diagnostic System (GDS) was used to test concentration and impulse control comparing 71 children with ADHD (61 boys, 10 girls; mean age 10.5 y) and 98 controls (65 boys, 23 girls; mean age 10.2 y). Differences were found between ADHD children and age- matched control children in each age group. The GDS scores were highly correlated with age with better a performance among the older children, which could support the relevance of the maturational lag hypothesis. · In Study IV a possible immature brain processing during concentration was studied comparing 36 children with ADHD (31 boys, 5 girls; mean age 10.5 y) and 63 controls (46 boys, 17 girls; mean age 10.0 y). QEEG techniques were used when the children performed the Vigilance Task of GDS. Compared to controls children with ADHD displayed specific differences in the pattern of frontal, temporal, and parietal brain activation. They had an enhanced slow cortical activity and decreased fast activity similar to younger children. These findings indicate a different arousal level in children with ADHD, which could be due to a delay in functional cortical maturation. · In Study V, impulsivity, brain processing and possible immaturity were studied. The same children with ADHD and controls as in study IV performed the Delay Task of GDS during registration of QEEG. In similarity to the results of study IV children with ADHD displayed different electrophysiological reactions, which may indicate that they, like younger children, have problems in cerebral processing when performing a mentally demanding task during a restricted time. · In Study VI, the "maturational lag" concept explaining ADHD was discussed over viewing previous and current literature on ADHD. The overview indicates that the DSM criteria of ADHD may be over- inclusive and shows that maturity and developmental aspects are important factors to be included in studies of ADHD. A slow speed in mental development may be of importance for the treatment and prognosis of ADHD. Conclusion. The over all results support the view, that some children with ADHD could represent a continuum of normal childhood behavior with maturational trajectories that are lagging behind and may catch up.