What is the best methodology for headache or migraine research? -- Clinical Scales for Headache and Migraine -- Reliability and Validity of Measurement of Clinical Scales -- PROMs in headache and migraine -- Measuring pain intensity in headache trials -- Clinical Scales for diagnosing and screening of headache and migraine -- Clinical Scales for disability, impact and burden in headache and migraine. Clinical Scales for health-related quality of life in headache and migraine: generic and disease-specific -- Clinical Scales for psychiatric comorbidities and cognitive processes in headache and migraine -- Clinical Scales for treatment monitoring and optimization in headache and migraine -- Other Questionnaires We Don't Want to Miss in Headache Studies -- Clinical Scales for Various Groups. .