Facial pain and other symptoms of temporomandibular disorders (TMD) are rather common in the adult population. According to clinical studies, psychological factors play an important role in the etiology and maintenance of these symptoms. On the other hand, chronic pain can cause depression. The aim of this study was to evaluate the association between symptoms of TMD and depression in a large population sample of young adults. The study was a part of the 31-year follow-up study of the Northern Finland Birth Cohort consisting of 12,058 live births from the year 1966. Questionnaire information concerning TMD symptoms was collected from a subsample of 5,696 subjects. Depression was measured with a question about reported depression (diagnosed by a doctor) and with the Symptom Checklist depression subscale (SCL-25 DS). Of the TMD symptoms, those related to pain had the most significant relations to indicators of depression. In both genders, the proportion of depression indicated with the SCL-25 DS was significantly higher in subjects with pain-related symptoms of TMD, i.e., facial pain and "pain at jaw rest", and in men with "pain on jaw movement", compared with non-pain subjects (p<0.05). Other symptoms of TMD also associated significantly with SCL-25 DS (p>0.05), except "difficulties in mouth opening" among women. Among women, the prevalence of recognized depression was also significantly higher in subjects with pain-related symptoms of TMD, compared with subjects with no pain (p< or =0.05). Almost all the associations remained significant after adjusting for marital status, education, and self-rated general health. In conclusion, the results show that depression has an association with TMD symptoms, especially those related to pain. When treating patients with facial pain, dentists should consider the possible presence of psychopathology and, if necessary, consult appropriate mental health professionals.