Two hundred chronic low-back pain patients entering a functional restoration program were assessed for current and lifetime psychiatric syndromes using a structured psychiatric interview to make DSM-III-R diagnoses. Results showed that, even when the somewhat controversial category of somatoform pain disorder was excluded, 77% of patients met lifetime diagnostic criteria and 59% demonstrated current symptoms for at least one psychiatric diagnosis. The most common of these were major depression, substance abuse, and anxiety disorders. In addition, 51% met criteria for at least one personality disorder. All of the prevalence rates were significantly greater than the base rate for the general population. Finally, and most importantly, of these patients with a positive lifetime history for psychiatric syndromes, 54% of those with depression, 94% of those with substance abuse, and 95% of those with anxiety disorders had experienced these syndromes before the onset of their back pain. These are the first results to indicate that certain psychiatric syndromes appear to precede chronic iow-back pain (substance abuse and anxiety disorders), whereas others (specifically, major depression) develop either before or after the onset of chronic low-back pain. Such findings substantially add to our understanding of causality and predisposition in the relationship between psychiatric disorders and chronic low-back pain. They also clearly reveal that clinicians should be aware of potentially high rates of emotional distress syndromes in chronic low-back pain and enlist mental health professionals to help maximize treatment outcomes.