MOLECULAR APPROACHES TO CHILD PSYCHOPATHOLOGY

Basic research into the genetics of childhood psychiatric disorders ha s substantially increased during the last two decades. Specific tic mu tations have been characterized in some developmental disorders (e.g., fragile X syndrome and Prader-Willi syndrome), but thus far identific ation of etiological gene mutations in psychiatric illnesses has been unsuccessful. Several psychiatric disorders serve as examples of the c urrent state of molecular approaches in child psychopathology. Investi gations to date of Gilles de la Tourette's syndrome (GTS) have not res ulted in the discovery of a gene of major effect. Some studies have im plicated the D2 and D4 dopamine receptors as having a direct role in t he etiology of GTS, but other studies have disputed those findings. Ho wever, the dopamine D2 receptor may modulate the severity of GTS. Obse ssive-compulsive disorder has a reported association with a low-activi ty allele of the enzyme catechol-O-methyltransferase; however, the low -activity genotype is also seen in a significant proportion of unaffec ted individuals. For reading disability two distinct phenotypes (phono logical awareness and single-word reading) have been linked to separat e loci on chromosomes 6 and 15, Attention deficit hyperactivity disord er (ADHD) has a reported association with the dopamine transporter, Fi ndings of a genetic locus for the personality trait of novelty seeking remain controversial.