McWilliams, et. al
Numerous studies have found pain conditions to be associated with self-reports of psychological distress and psychiatric disorders. Several important clinical implications of these associations have been noted. For example, information regarding specific patterns of comorbidity could guide clinicians' efforts to detect psychiatric disorders in patients with pain. As well, psychopathology (i.e. depression) has been found to be associated with poor pain-related outcomes such as elevated pain intensity, functional limitations, and non-recovery (see Bair et al., 2003).
McWilliams et al. (2003) found significant associations between arthritis and each of the mood and anxiety disorders considered. Given the lack of attention to anxiety disorders in the pain literature, it was particularly noteworthy that the associations between arthritis and several of the anxiety disorders (i.e. panic disorder and posttraumatic stress disorder) were stronger than the association between arthritis and depression. Evidence from other epidemiological studies indicates that migraine may also be more strongly associated with anxiety disorders, particularly panic disorder (e.g. Breslau and Davis, 1993 and Swartz et al., 2000) and generalized anxiety disorder (GAD) (e.g. Merikangas et al., 1990), than with depression. The present study utilized data from another nationally representative sample, the Midlife Development in the United States Survey (MIDUS), in an attempt to replicate these earlier findings with arthritis and migraine and to extend this line of investigation to back pain. It was hypothesized that each of these pain conditions would be significantly associated with the psychiatric disorders included in the MIDUS and that each pain condition would be more strongly associated with the anxiety disorders than with depression.
Data from the MIDUS yielded significant positive associations between three pain conditions (arthritis, migraine, and back pain) and common mood and anxiety disorders (depression, panic attacks, and GAD). Multivariate logistic regression analyses indicated that these associations remained after adjusting for a wide range of potential confounding variables including age, gender, education level, race, and the presence of another pain condition. These findings were noteworthy because previous epidemiological studies concerning psychopathology and both migraine (e.g. Merikangas et al., 1990 and Stewart et al., 1994) and arthritis (e.g. McWilliams et al., 2003) have generally not adjusted for comorbid pain conditions.
Medical or health conditions that do not primarily involve pain are also associated with psychopathology (e.g. Wells et al., 1988). A third series of analyses examined whether each pain condition could account for unique variance in the psychiatric disorders beyond that accounted for by the number of other medical/health conditions present. The majority of the associations remained statistically significant, but the association between arthritis and panic attacks and the association between back pain and GAD did not. This pattern of findings raises the possibility that the association between arthritis and panic attacks and the association between back pain and GAD found in Models 1 and 2 reflect a more general association between health problems and psychopathology rather than more specific associations between these respective pain conditions and psychiatric disorders. Several of the other medical conditions included (e.g. recurring stomach problems) likely involved pain, so it is possible that the third set of analyses also adjusted for the presence of other forms of pain. Nonetheless, this procedure was used because the focus of the study was on three types of pain (rather than pain in general) and the goal of these analyses was to adjust for other medical and health conditions regardless of whether they involved some pain.
Consistent with previous studies, depression was significantly associated with each of the pain conditions. Based on previous research demonstrating substantial comorbidity between mood and anxiety disorders (e.g. Krueger, 1999 and Vollebergh et al., 2001), it was expected that anxiety disorders would also be associated with the pain conditions. Furthermore, several studies (e.g. Breslau and Davis, 1993; McWilliams et al., 2003 and Merikangas et al., 1990) have found pain conditions to be more strongly associated with several anxiety disorders than with depression. The present study replicated this pattern of findings and extended it to back pain. The bivariate odds ratios clearly indicated that each pain condition was more strongly associated with the anxiety disorders than with depression. However, this pattern was less consistent in the analyses that adjusted for other medical/health conditions. Three additional logistic regression analyses were used to examine whether the association between multiple pain conditions and psychopathology would be greater than the associations between pure pain conditions (i.e. those with only one pain condition) and psychopathology. The overall pattern was consistent with previous research (e.g. Dworkin et al., 1990) indicating that those with multiple physical complaints have higher rates of psychopathology than those without a physical complaint or those with a single complaint.
There is a paucity of research or clinical literature concerning anxiety disorders in relation to pain conditions. The findings of this and earlier studies suggest that such attention is warranted. More sophisticated approaches to the assessment of anxiety are required in pain-related contexts. For example, a recent issue of Arthritis Care and Research focused on assessment issues included an article on depression (Smarr, 2003), but anxiety was only addressed in an article considering ‘other measures of psychological well-being’ ( Schiaffino, 2003). Furthermore, the anxiety measure selected was the State-Trait Anxiety Inventory ( Spielberger, 1983), which includes numerous depression-related items (see Bieling et al., 1998), and appears to be more accurately described as a measure of general distress. Several self-report measures designed to assess symptoms or constructs directly related to specific anxiety disorders are available. Examples include the Penn State Worry Questionnaire ( Meyer et al., 1990) for GAD and the Mobility Inventory ( Chambless et al., 1985) for agoraphobia. As well, the CIDI-SF could readily be incorporated into assessment procedures and represents a successful compromise between the need for diagnostic-specific assessment procedures and the time constraints found in many contexts.
Temporal relationships between pain conditions and depression have long been of interest (see Fishbain et al., 1997). However, the temporal relationships between pain conditions and anxiety disorders remains largely ignored. Breslau and Davis's (1993) longitudinal study of the association between migraine and psychopathology in a community sample of young adults provides a rare exception to this general rule. They found that individuals who reported having their last migraine a year or more prior to the baseline interview were at increased risk of experiencing first incidence depression and panic disorder at a 14-month follow up. These findings suggest that depression, panic, and migraine share common predispositions and that mood and anxiety disorders are not merely the psychological consequences of a pain condition. Causal relations between anxiety and most other pain conditions have not been investigated.
Theories regarding underlying factors involved in both pain and anxiety disorders have focused on neurochemical mechanisms (e.g. Merikangas et al., 1990). Asmundson et al. (2002) reviewed several potential shared psychological vulnerabilities for posttraumatic stress disorder and pain and noted hyperarousal, hypervigilance, and attentional biases towards somatic cues may be involved in both conditions. These factors have also been implicated in other anxiety disorders, particularly panic disorder, and may be responsible for the associations observed in the present study. Recent conceptualizations of GAD have suggested that worry may be used to suppress somatic anxiety or the hyperarousal associated with perceptions of threat ( Borkovec et al., 2004). It is possible that individuals with pain conditions may use worry as a strategy for reducing somatic arousal associated with pain, and as a result may become prone to developing GAD.
The treatment implications of the associations between pain and psychiatric disorders have focused on pharmacologic interventions (e.g. Stewart et al., 1994). However, in light of their possible shared psychological vulnerabilities, psychological interventions also hold potential for treating comorbid pain and psychiatric disorders. It is noteworthy that psychosocial interventions for psychiatric disorders and pain conditions share several common elements. For example, treatments for depression and pain both focus on increasing activity levels and treatments for anxiety and pain both include strategies for reducing arousal (i.e. relaxation training). It may be possible to develop integrated psychological treatments for both conditions. As well, evidence concerning the temporal relationships between disorders may provide direction in terms of prevention efforts. For example, the findings of Breslau and Davis (1993) suggest that those with a history of migraine would be an appropriate group at which to target anxiety disorder prevention efforts.