The link between diabetes and schizophrenia: an immunological explanation

Genomic imprinting in the development and evolution of psychotic spectrum conditions

I review and evaluate genetic and genomic evidence salient to the hypothesis that the development and evolution of psychotic spectrum conditions have been mediated in part by alterations of imprinted genes expressed in the brain. Evidence from the genetics and genomics of schizophrenia, bipolar disorder, major depression, Prader-Willi syndrome, Klinefelter syndrome, and other neurogenetic conditions support the hypothesis that the etiologies of psychotic spectrum conditions commonly involve genetic and epigenetic imbalances in the effects of imprinted genes, with a bias towards increased relative effects from imprinted genes with maternal expression or other genes favouring maternal interests. By contrast, autistic spectrum conditions, including Kanner autism, Asperger syndrome, Rett syndrome, Turner syndrome, Angelman syndrome, and Beckwith-Wiedemann syndrome, commonly engender increased relative effects from paternally expressed imprinted genes, or reduced effects from genes favouring maternal interests. Imprinted-gene effects on the etiologies of autistic and psychotic spectrum conditions parallel the diametric effects of imprinted genes in placental and foetal development, in that psychotic spectrum conditions tend to be associated with undergrowth and relatively-slow brain development, whereas some autistic spectrum conditions involve brain and body overgrowth, especially in foetal development and early childhood. An important role for imprinted genes in the etiologies of psychotic and autistic spectrum conditions is consistent with neurodevelopmental models of these disorders, and with predictions from the conflict theory of genomic imprinting.

Atypical antipsychotic agents and increased risk of diabetes: class action or differential action?

Atypical antipsychotic (AAP) agents are useful in treating patients with schizophrenia and other psychosis. Their advantages are the low incidence of extrapyramidal side effects, and possible amelioration of negative, cognitive and mood symptoms. Occurrence of diabetes after AAP drug administration is of concern as patients do not often recognise their symptoms, physicians may fail to diagnose early, with consequent morbidity and mortality. The symptoms of psychosis, including lack of insight and motivation, may decrease the ability of schizophrenic patients to communicate potential health problems. Whether or not AAP drugs induce diabetes and, if they do, if it is a class action or a differential action, is often debated. Clinical evidence on AAP drug-induced diabetes is mounting. With their discontinuation, the diabetes often dissipates, but reappears when they are started again, thereby implicating the AAP drugs in the development of diabetes. There is still dispute regarding the differential effect of the various AAP drugs in their ability to produce diabetes. Although not scientifically proven, available evidence seems to indicate that clozapine and olanzapine may have a higher propensity to induce diabetes compared with other AAP drugs.

Relationship of Atypical Antipsychotics with Development of Diabetes Mellitus

OBJECTIVE

To review the pharmacoepidemiologic evidence for the link between exposure to atypical antipsychotics and the development of diabetes mellitus.

DATA SOURCES

A MEDLINE search (1990-March 2003) was conducted.

STUDY SELECTION AND DATA EXTRACTION

The search was limited to articles that described findings from analyses of large databases and used the words diabetes or hyperglycemia, and antipsychotic or clozapine or olanzapine or risperidone or quetiapine or ziprasidone or aripiprazole in the title or abstract. The odds ratio or relative risk, together with their corresponding confidence interval, was extracted.

DATA SYNTHESIS

Results are conflicting, and this variability may be due to the different populations studied, different study designs, and the possibility of publication bias related to funding by the pharmaceutical industry. Nevertheless, an increased risk for diabetes mellitus appears to be present for patients receiving atypical antipsychotics. However, differential risk among the atypical antipsychotics is difficult to ascertain.

CONCLUSIONS

Clinicians are urged to manage risk by regularly monitoring all patients receiving atypical antipsychotics for the emergence of diabetes mellitus. Future studies should carefully control for confounding variables such as age, diagnosis, change in weight, activity level, family history, and ethnicity.