## 4 Discussion
This correlation may be owing to the greater muscle tension and tenderness that was already demonstrated in the patients with migraine and comorbid depression [23; 24]. In addition, motivational factors during the assessment could be involved. The results of this study should be interpreted with caution, as the correlations between cervical ROM and depressive levels were weak. Moreover, the wide confidence intervals ranging from \(-0.54\) to \(-0.05\), meant that the correlations could be considered between moderate and weak; however, they even presented a correlation close to \(0\), which indicates the absence of any correlation between these variables. Further, other associated factors observed in patients with both migraine and depression, such as fibromyalgia [21] and medication overuse [20], were excluded and could increment the correlation results. To the best of our knowledge, there is no published report regarding a significant correlation between cervical ROM and depression in patients with headache or neck pain. However, cervical ROM appears to be weakly to moderately correlated with patient-reported outcome measures, such as pain and neck-related disability [18; 48; 49; 50]. Based on these findings, we assumed that the clinical implication of the results might be limited since the values of the association coefficients were low. In addition, cervical range of motion may be influenced by other factors that we did not control in this study, such as head and neck posture and type of work occupation, for example. The absence of significant correlations between cervical ROM and pain and disability-related measures suggests that the cervical ROM may be just an impairment not immediately related to the clinical presentation of migraine or neck pain. It means that a unique impairment does not necessarily characterize a cervical musculoskeletal disorder. Although the pain cannot be a determinant factor to characterize a musculoskeletal disorder overall, it is suggested that cervical disorders would be better defined by a combination of neck pain and a cluster of symptoms and impairments of body function [51]. Another aspect that might contribute to the absence of significant correlation between cervical ROM and pain- and disability-related variables is the range of cervical ROM observed in our cohort. We did not have a control group without pain to assume any restriction of cervical ROM. However, using distinct methods for measuring the ROM reference data from controls, as reported by [PERSON] et al. (2019) [17] in their metanalysis, could be of benefit to our understanding. The median and interquartile ranges of our cohort's ROM at the sagittal and transverse planes are predominantly lower than their respective means in the referred metanalysis. This suggests that the majority of our cohort would be classified as having a limited ROM at the sagittal and transverse planes. A cohort with a narrow range composed mostly of those with restricted ROM would not properly reflect a linear correlation. The fear-avoidance model of pain suggests that when pain is perceived as harmful, this may lead to catastrophic thoughts, which generate fear of movement-related pain that in turn leads to avoidance of activities, resulting in disability [38]. Previous reports in patients with neck pain support this model and have demonstrated a significant correlation between TSK and cervical ROM in individuals with neck pain [47; 48]. However, in our sample, the active cervical ROM did not present a significant linear correlation with the fear of movement-related pain measured by TSK, even when more than 40% of the sample reported neck pain during active cervical movement. Behavioral and physical factors involved in these assessments may play a complex role in patients with migraine.