Serotonin and Neuropeptides in Blood From Episodic and Chronic Migraine and Cluster Headache Patients in Case-Control and Case-Crossover Settings: A Systematic Review and Meta-Analysis.

Potential migraine and CH signaling molecule profiles and biomarkers were revealed. Nevertheless, the high degree of heterogeneity between studies impedes identification of valid biomarkers but allowed us to assess the presence of confounders. Consideration of the potential confounders identified in this SR-MA might be of importance in the experimental planning of future studies. This consideration could be incorporated through establishment of specific guidelines.