title: Naturalistic study designs in samples with refractory pain: advantages and limitations.
authors.forename: Rollin M
authors.initials: RM
authors.lastname: Gallagher
mesh_terms: D002986:Clinical Trials as Topic; D015928:Cognitive Behavioral Therapy / Q000379:methods*; D006261:Headache / Q000523:psychology / Q000628:therapy; D006801:Humans; D010148:Intractable Pain / Q000523:psychology* / Q000628:therapy; D012107:Research Design