Anticipation refers to the increase in disease severity or decrease in age of onset in successive generations. The concept evolved from the theories and dogma of degeneration that were pervasive in psychiatry and medicine in the late 19th century and into the early 20th century. The term was set aside with the criticism of geneticist Lionel Penrose, who argued that anticipation was the result of ascertainment biases. The renewed interest in anticipation followed the identification of its molecular genetic basis in the form of unstable trinucleotide repeats. Subsequently, several diseases have been studied clinically for the presence of anticipation. Although anticipation has been identified in many diseases, including bipolar disorder, only diseases showing a pattern of progressive neurodegeneration have been associated with unstable trinucleotide repeats. This review summarizes the research on anticipation in bipolar disorder and other secular trends in the patterns of the illness such as the cohort effect. The changing nature of bipolar disorder is likely to be a result of combined influences from several genes, some of which are likely to be in a state of flux, as well as environmental or cultural forces that converge to give the clinical picture of anticipation.

Elucidation of genetic factors in schizophrenia and bipolar disorder remains a challenging task to psychiatric researchers. As a rule, data from genetic linkage and association studies are quite controversial. In this article, we further explore the possibility that in addition to DNA sequence variation, a putative epigenetic dysregulation of brain genes plays an important role in the etiopathogenesis of major psychosis. We provide an epigenetic interpretation of unclear genetic findings specifically pertaining to chromosome 22 in schizophrenia and bipolar disorder. It is suggested that epigenetic strategies, when applied in conjunction with traditional genetic ones, may significantly expedite the uncovering of the molecular causes of major psychosis.

Psychiatric genetics, while promising to unravel the mechanisms of psychiatric disorders, has proven to be a challenging field. Psychiatric disorders, like other common genetic traits, are complex and heterogeneous. Psychiatric genetics has also suffered from a lack of quantifiable, biology-based phenotypes. However, the field is currently at an opportune moment. The work of various investigators is on the verge of paying rich dividends. Efforts at positional cloning are being greatly accelerated by the fruits of the Human Genome Project. New tools of functional genomics, such as expression profiling and proteomics, are being applied to animal models. These two methods can complement each other in an approach we have termed convergent functional genomics. Lastly, improvements in the measurement of biologically distinct endophenotypes—or phenomics—will lead to a better understanding of the mapping of genes to phenotypes in both animal and human systems.

A growing family of medications is used for mood stabilization in bipolar disorder. These medications fall into two broad categories according to likely mechanisms of action. Within the categories, specific drugs may vary in their efficacy for different phases of the disorder. The first category, including lithium, anticonvulsants, and some novel treatments, appears to have mechanisms related to intracellular second messengers. These medications have more pronounced antimanic than antidepressant effects, except for lamotrigine, which has antidepressant effects without precipitating mania. The second group of mood stabilizers is the atypical antipsychotics, which act through dopamine and other monoamines. Olanzapine and in all likelihood other drugs in the class possess marked, acute antimanic properties and possible antidepressant properties, but require further study before they can be used as routine options in long-term care. It is clear that the advent of multiple mood stabilizer candidates has not yet led to a single ideal therapy for bipolar disorder, but rather to options that can be flexibly tailored to the lifetime needs of individual patients, in sequences or combinations, and perhaps in conjunction with other classes of psychotropics.