Factors Associated With Migraine Refractoriness to Preventive Treatments: Psychological Aspects and Relationship With Components of the Endocannabinoid System

Migraine is a common and highly disabling condition, representing the second-leading cause of disability in the global ranking of most disabling diseases . In the majority of individuals, the disease manifests as episodic (EM), with attacks recurring weekly or monthly. In a smaller (2-3% of the general population), but still significant portion of patients, migraine becomes chronic, i.e., occurring on at least 15 days per month (CM).

Previous studies have shown that CM patients are characterized by the presence of multiple psychiatric comorbidities compared with subjects with episodic migraine and healthy controls. In recent years, it has also been shown that among the neurobiological systems involved in the genesis and development of mental disorders, the endocannabinoid system (ES) appears to play an active role. In particular, patients with these disorders are characterized, at the level of peripheral cells, by a gene alteration of cannabinoid receptors.

Several studies reported the involvement of SE in immune responses, psychological processes, transduction of neurobiological signals and pain, including migraine pain. Recently it has been shown that the peripheral gene expression of enzymes involved in the metabolism of anandamide (AEA) and 2-aciglycerol (2-AG), the two best known endocannabinoids, is altered in migraine patients, but more markedly in the chronic subtype, suggesting a role for these lipid molecules not only in the pathophysiology of the disease, but also in its exacerbation. The role of CGRP in the pathophysiology of migraine has now been demonstrated, although the mechanism of action at both peripheral and central levels and its possible interactions with other pathways are not completely known.

The term "refractory" migraine describes a particularly aggressive form of the disease in which the patient does not benefit from any of the preventive therapies with the various classes of drugs available, including treatment with monoclonal antibodies directed against CGRP (Consensus document of the European Headache Federation).

Anxiety, depressive symptoms, somatization, and pain hypersensitivity are significantly more prevalent in refractory migraineurs than in non-refractory subjects who benefit from preventive therapies, suggesting that these symptoms may contribute to treatment refractoriness. Recently, in a preliminary study regarding the efficacy of monoclonal antibody targeting CGRP in CM patients refractory to at least three preventive therapies,the investigators showed a higher prevalence of personality disorders (77% vs 37%) in those who were not responding to treatment at 1 year (non-responders: reduction in migraine days <50%), compared with those who were responding (responders: reduction in migraine days ≥50%). Non-responders were also characterized by a higher prevalence of anxiety spectrum disorders and more stressful events than responders. These data, although preliminary, point to a more psychologically complicated picture in non-responder patients compared with responders. To date, however, no neurobiological data are available to explain how psychological comorbidities may contribute to treatment refractoriness.