Journal of Oral & Facial Pain and Headache 381 Psychosocial Scores and Jaw Muscle Activity in Women Aims: To test whether women with temporomandibular disorder (TMD)–related pain showed higher psychosocial scores and higher awake- and sleep-time jaw muscle activities (characterized by duty factors) compared to pain-free controls and whether psychosocial scores and the jaw muscle duty factors were associated. Methods: Subjects gave informed consent to participate. The Diagnostic Criteria for TMD (DC/TMD) were used for diagnosis of TMD pain, and 31 and 36 women were included in the TMD-related pain and control groups, respectively. DC/TMD Axis II instruments were used to determine psychosocial scores. Subjects self-recorded masseter and anterior temporalis electromyography (EMG) over 3 days and 3 nights. The duty factor (time of muscle activity/total recording time [%]) was quantified using subject-specific EMG/bite-force calibration via data recorded in the laboratory. Group differences (α = .05) were assessed for psychosocial scores and duty factors using chi- square and two-sample t tests. Linear regression assessed whether psychosocial scores were associated with duty factors. Results: Average duty factors were ≤ 2.4% for awake and sleep times in both muscles, and between-group comparisons showed no significant differences. For physical symptom scores, there were significantly fewer TMD-related pain subjects in the normal category and significantly more in the moderate-severe category (all P < .01) compared to controls. Subjects with elevated compared to normal psychosocial scores showed significantly higher jaw muscle duty factors by ≥ 1.5-fold. Conclusion: A significantly larger proportion of TMD-related pain subjects compared to control subjects had moderate-severe physical symptom scores. Awake- and sleep-time jaw muscle duty factors were not different between groups and were generally low among all subjects. Additionally, higher than normal psychosocial scores were associated with significantly more low-magnitude jaw muscle activity. J Oral Facial Pain Headache 2018;32:381–388. doi: 10.11607/ofph.2133 Keywords: bruxism, EMG, jaw muscle, pain, psychosocial factors, TMD P arafunctional jaw muscle activity is regarded as both a cause and a consequence of TMD-related pain. 1,2 In addition, it is thought that common mental health states such as somatization, anxi- ety, and depression are associated with the onset and development of chronic TMD-related pain. 3,4 Previous pilot studies have shown in- creased low-level awake-time jaw muscle activities in subjects with TMD-related pain 5 compared to subjects without TMD pain and in subjects with self-reported somatic and depression symptoms 6 com- pared to subjects without these symptoms. Also, a recent systematic review 7 assessed the evidence for the association between psychoso- cial states and development of TMD-related pain due to increased jaw muscle activities. Although co-occurrence of these states with pain and jaw muscle dysfunction was found, no clear suggestions about cau- sality were possible due to the lack of quantitative data characterizing muscle activities during the day and night, control groups, repeated measures, and validation of instrument accuracy. Quantitative analysis of polysomnography 8,9 and ambulatory awake- and sleep-time jaw muscle electromyography (EMG) 10,11 showed that jaw behaviors rarely produced large mandibular loads. For example, Yoly M. Gonzalez, DDS, MS, MPH Associate Professor Department of Oral Diagnostic Sciences School of Dental Medicine State University of New York at Buffalo Buffalo, New York, USA Jeffrey C. Nickel, DMD, MSc, PhD Associate Professor Department of Orthodontics School of Dentistry Oregon Health & Science University Portland, Oregon, USA JoAnna M. Scott, MS, PhD Assistant Professor Office of Research & Graduate Programs School of Dentistry University of Missouri Kansas City Kansas City, Missouri, USA Hongzeng Liu, PhD Senior Research Associate Department of Orthodontics School of Dentistry Oregon Health & Science University Portland, Oregon, USA Laura R. Iwasaki, DDS, MSc, PhD Associate Professor Department of Orthodontics School of Dentistry Oregon Health & Science University Portland, Oregon, USA Correspondence to: Dr Laura Iwasaki 2730 SW Moody Avenue, SDORTHO Portland, OR 97201 Fax: 503-494-5777 Email: iwasaki@ohsu.edu ©2018 by Quintessence Publishing Co Inc. © 2018 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.