State and trait markers to define the continuum of affective disorders.

Recently a substantial body of biological evidence, converging data from biochemistry, neurophysiology, pharmacology, immunology, and neuroimaging has been collected to underpin the concept of continuum of affective disorders. Overall, it is comprised of two dimensions. One is clinical, which spans from major depressive disorder to bipolar spectrum, with mixed and sub-threshold states. The other dimension is causal, based mainly on evidence about the heterogenous etiological structure of mood disorders, including organic and exogenous brain disorders (such as multiple sclerosis, neurodegenerative diseases, intoxications) manifested in prodromal stages with affective disturbances, and "functional" or endogenous mood disorders. This Special Issue will explore the trait and state complex markers which define the continuum of affective disorders in both causal and clinical perspective.