Alpha 2 adrenergic receptor subtypes in depression: a candidate gene study

Association study of the adrenergic receptors and childhood-onset mood disorders in Hungarian families

The adrenergic system has been implicated in the etiology of depression based on a number of lines of evidence, particularly, the mechanism of some classes of antidepressants which increase the synaptic levels of norepinephrine. Further, several genome scans for mood disorders, both unipolar and bipolar, have indicated linkage to the chromosomal regions of 5q23-q33.3, 8p12-p11.2, 4p16, and 10q24-q26, the location of the adrenergic receptors alpha1B (ADRA1B), beta3 (ADRB3), alpha2C (ADRA2C), alpha2A (ADRA2A), and beta1 (ADRB1). In this manuscript, we report on the relationship of the adrenergic receptors and depression using a family based association approach and 189 families (223 affected children) with childhood-onset mood disorder (COMD) collected in Hungary. We found no significant evidence for an association with any of the 24 markers, in total, tested across these genes using single marker analysis or haplotypes of markers across these genes. The results in the present sample indicate that these nine genes are unlikely to be major susceptibility genes contributing to COMD.

The genetics of major depressive disorder

There is consistent evidence that major depression is familial and population-based twin studies as well as hospital register-based twin studies find substantial heritability. However, there is also a large proportion of variation in liability left to be explained by nongenetic factors. Although there seems little doubt that life events play a role in precipitating depression, studies that have attempted to examine familial liability along with social adversity find that environmental measures tend to be contaminated by genetic effects. Thus, the tendency to experience (or report) life events appears to be influenced by shared family environment, and for certain types of events there is a genetic component. The molecular genetic basis of liability to depression is an under-researched area, but some candidate gene studies show potentially promising results. Systematic mapping studies aiming to cover the entire genome are currently being launched.