Glial pathology is modified by age in mood disorders--a systematic meta-analysis of serum S100B in vivo studies

Mood disorders are characterized by specific glial pathology. Recently, based on histopathological post mortem studies, the glial hypothesis has been discussed as a dynamic process, in particular with regard to glioplasticity. Whereas in young subjects with mood disorders, glial cell density or glial cell numbers are reduced, they are increased in elderly subjects.

To validate this concept in vivo, we investigated the dynamic course of glial pathology in mood disorders across studies measuring the glial marker protein S100B in serum in a systematic and quantitative meta-analysis according to the QUOROM and PRISMA statement. We searched for studies in PubMed and Medline, applied strict inclusion/exclusion criteria, and calculated effect sizes according to Cohen and Hedges.

The final meta-analysis included 174 subjects with mood disorders and 102 control subjects. It demonstrated higher levels of the glial marker protein S100B in older compared with younger adult subjects suffering from mood disorders, although both young and older subjects showed elevated values in comparison to control subjects. Illness duration and age at onset had no impact on serum S100B.

Influences of antidepressive drugs vs. the spontaneous course of the illness, differences between mood disorder subtypes and the specific role of S100B have to be investigated in future longitudinal studies.

The meta-analysis indicates a modifying effect of S100B in mood disorders in the interaction with age, with an increasing role across the lifespan. Results are relevant for the understanding of mood disorders and future illness modifying therapies because S100B may influence neuro- and glioplasticity.