Molecular genetic studies of complex disorders require a number of parallel strategies. Many of the more familial psychiatric syndromes are highly prevalent and may represent a collection of a number of distinct genetic subtypes and possibly a number of nongenetic subtypes. A nongenetic form of illness may appear clinically indistinguishable from a genetic form. These nongenetic subtypes of a syndrome would be considered phenocopies. In this and the subsequent issue of CNS Spectrums, a number of papers are presented that review the current state of psychiatric genetics of major disorders. Clinical strategies to narrow phenotypes and better define study populations are paired with laboratory and statistical strategies to optimize both candidate gene and genome scanning methods.

In this issue, Kennedy and colleagues focus on a review of the genetics of schizophrenia, highlighting genome scans already completed and studies on special populations. Schindler and colleagues present a unique and efficient method for defining the homogeneity of a study population, surname analysis, and the importance of population selection in the design of genetic studies. Macedo and colleagues demonstrate the study of anticipation in bipolar mood disorder. Genetic anticipation is the observation of an earlier age of onset and greater disease severity in younger generations. This pattern has been associated with dynamic repeat expansions in the DNA in several neuropsychiatric disorders, and represents a good example of a unique genetic mechanism causing a unique phenotypic pattern. Nicolini and colleagues present work done to date on obsessive-compulsive disorder.