by Michael D. Anestis, M.S.
One of the concerns expressed most frequently by individuals who do not believe that scientific research should drive clinical work is that the clients treated in research studies often are hand picked such that they only meet criteria for one diagnosis whereas, in "real world" practice, clients tend to meet criteria for more than one ("comorbidity"). This is, of course, a legitimate concern that speaks to the degree to which what we learn in research generalizes to standard clinical care. An important point to keep in mind, however, is that only efficacy studies - studies in which the utility of a treatment is first established - exclude such participants. In effectiveness studies - studies in which efficacious treatments are tested in standard clinical environments - those restrictions are not in place. We have covered several effectiveness studies in prior PBB articles, but today I would like to more directly address the issue of comorbid diagnoses. To do this, I would like to discuss an "in press" study to be published in Behavior Therapy by Michelle Newman, Amy Przeworski, Aaron Fisher, and Tom Borkovec of Pennsylvania State University.
The authors opened their article by pointing out that the majority of clients who meet criteria for a principle diagnosis of an anxiety disorder also meet criteria for at least one additional mood or anxiety disorder (e.g., Brown & Barlow, 1992). In generalized anxiety disorder (GAD), it is estimated that 45% to 98% of clients also meet criteria for another diagnosis (Goisman, Goldenberg, Vasile, & Keller, 1995). Taking this point even further, individuals with GAD comorbid with another diagnosis report:
- Greater number of disability days (Hunt, Issakidis, & Andrews, 2002)
- More interference as a result of their GAD symptoms (Wittchen, Zhao, Kessler, & Eaton, 1994)
- Increased interpersonal problems (Judd et al., 1998)
- Greater likelihood of seeking professional help (e.g., Bland, Newman, & Orn, 1997)
- Greater suicide risk (Bordon, Fergusson, & Horwood, 2007)
- More hospitalizations, visits to emergency rooms, consultations with medical professionals, laboratory tests, medication use, and work absenteeism (Souetre et al., 1994)
Clearly then, meeting criteria for another diagnosis in addition to a principle diagnosis of GAD is associated with a number of problematic outcomes. That being said, it makes sense to investigate the degree to which such individuals respond to treatment as well as individuals who only meet criteria for GAD. After all, if comorbidity is the norm and such individuals do not respond to empirically supported treatments (ESTs), than those who oppose an emphasis on science would be correct in their questioning of the EST movement's applicability to standard mental health care.
Prior to the Newman et al (in press) study, only a handful of researchers had investigated this question and their results have been mixed. Durham, Allan, and Hackett (1997) found that comorbid Axis I diagnoses predicted poorer initial outcome for individuals with GAD who received cognitive therapy, analytic therapy, or anxiety management training. Crits-Christoph and colleagues (2004) found that comorbid depression predicted a diminished response to brief psychodynamic or supportive nondirective therapy for GAD. Contrary to these findings, however, Butler and Anastasiades (2008) found that comorbid panic disorder did not influence treatment outcomes and Wetherell and colleagues (2005) found that older adults receiving group cognitive behavioral therapy (CBT) who had comorbid diagnoses responded to treatment better than did individuals with pure GAD.
On a similar note, only one prior study has tested the impact of psychotherapy for GAD on comorbid diagnoses. This question is also important; after all, it seems worthwhile to learn whether all of a client's symptoms are impacted by treatment or whether the clinician might need to switch gears after addressing GAD in order to fully impact the entire breadth of the client's symptomatology. In the one prior study on this topic, Borkovec, Abel, and Newman (1995) found that clients who received supportive listening, applied relaxation, or CBT experienced a reduction in the number of comorbid diagnoses, particularly if they no longer met criteria for GAD following treatment and at follow-up.
Each of these prior studies had important points of weakness. For instance, many excluded any participants with comorbid depression, obsessive-compulsive disorder, or chronic levels of GAD. In others, a large proportion of the sample was currently taking psychotropic medications that were not being managed and held consistent by doctors, thereby diminishing our ability to fully understand the degree to which treatment itself was influencing results. The studies also did not include follow-up periods of more than a year, so it was impossible to fully understand the long term impact of treatment. To address all of these factors, Newman and colleagues (in press) designed a study in which individuals who met criteria for a primary diagnosis of GAD received 14 sessions of cognitive therapy, behavioral therapy, or CBT. The exclusion criteria indicated that only participants with comorbid panic disorder (which has been shown not to impact treatment outcome), substance abuse, psychosis, organic brain syndrome, or severe depression or who were on antidepressants were ineligible. Only two participants in the sample were taking anti-anxiety medications and they agreed to keep their dosage constant throughout treatments. All individuals were assessed throughout treatment, at 6-month follow-up, at one year follow-up, and at two-year follow-up.
In total, there were 76 participants in the study, 63 of whom were assessed at all time points, including two year follow-up. Before treatment began, 60.5% of the sample met criteria for at least one diagnosis in addition to GAD. The most common comorbid diagnoses were social anxiety disorder, simple phobia, depression, dysthymia, PTSD, and agoraphobia. Of those with a comorbid diagnosis, 78.3% had only one, 15.2% had two, and 6.5% had three or more. Seven people dropped out of therapy before it was completed. Although the difference was not statistically significant, there was a trend (p = .07) for individuals with comorbid diagnoses to be less likely to drop out of treatment than individuals with pure GAD.
What about results? Individuals with comorbid diagnoses reported more severe symptoms of GAD at pretreatment than did individuals with pure GAD; however, such individuals also exhibited a greater rate of change from pre-treatment to post-treatment. In other words, contrary to the fears of individuals who claim that research does not apply to clinical work and that ESTs only work on individuals with uncomplicated diagnostic presentations, individuals with comorbid diagnoses fared better in treatment than did individuals with pure GAD. By post-treatment, symptom levels in individuals with comorbidities were on par with those of individuals with pure GAD. Not only that, but the gains on GAD symptoms were maintained at one and two year follow-ups. Severity of comorbidity did not impact treatment gains either, so the argument can not be made that this simply reflects individuals with minor, unsubstantial comorbidities benefiting from treatment. Score one for science and empirical data there.
What about the impact of treatment on comorbid diagnoses? Results indicated that, over the course of treatment, symptoms of depression, social anxiety disorder, and simple phobia were all significantly reduced. So, even though the treatment was aimed specifically at reducing symptoms of GAD, symptoms of comorbid diagnoses were also substantially addressed. This, of course, weakens the common argument that ESTs maintain too narrow of a focus and leave clients unlikely to experience a broader, far reaching type of treatment gain (and of course, there is no evidence that alternative approaches are any better at addressing this issue). Over the follow-up period, these results remained consistently, although not universally, true. At the two year follow-up assessment, reductions in social anxiety disorder and simple phobia symptoms remained significant; however, reductions in depression did not. So, ultimately, these results indicate that CBT for a primary diagnosis of GAD can immediately impact symptoms of other anxiety disorder as well as depression, but that the treatment gains for depression might not hold over an extended period of time, thereby necessitating additional treatment.
To put these results in a little bit clearer perspective, let me provide you with some numbers. At pre-treatment, 40 (63.5%) of the 63 participants assessed at all time points met criteria for a comorbid diagnosis in addition to GAD. Post-treatment, only 6 (9.5%) met criteria for a comorbid disorder. At 6-month follow-up, only 3 (4.8%) met criteria for a comorbid disorder. At one year follow-up, 6 (9.5%) met criteria for a comorbid diagnosis. At two year follow-up, 12 (19%) met criteria for a comorbid diagnosis. Certainly, it is less than ideal that, by two years, the numbers had increased from earlier results; however, it would be impossible to look at these numbers and conclude that CBT - a treatment developed through scientific investigation - does not produce strong results in "real world" practice, particularly given that the results for CBT in the treatment of GAD pale in comparison to the results of CBT in the treatment of other disorders (e.g., depression, bulimia nervosa, panic disorder).
An astute statistician might look at these findings and wonder if the promising results for comorbid individuals simply represent regression to the mean. There is a tendency for individuals who exhibit an extremely high or low score on a measure at one time point to exhibit a more moderate score at the next assessment regardless of intervention, experience, or other related factors. GAD, however, is a chronic disorder with a low likelihood of naturalistic remission (Yonkers et al., 1996) and, as such, it is highly unlikely that more severely impaired individuals fared better in treatment simply because their severe symptoms were more likely to go away on their own.
There are certainly other limitations to this study. CBT (and its components) was not compared to another active treatment or a waitlist control group. Additionally, although the exclusion criteria were not particularly strict, some did remain, so future work without any would yield useful information. The sample size in this study was quite small, which limits the statistical power of the analyses and might have resulted in an understatement of the results.
Summary
So what was the point in all of this? What can be learned from these results that is of obvious use to everyone reading this article? The most important lesson is that, despite the claims of those who trivialize the use of research to guide clinical practice, the forms of therapy that receive empirical support through scientific investigation are not limited in their utility to individuals with simple, less severe presentations. In fact, these results seem to indicate that more severe and complicated cases benefit the most from CBT. Time and time again this point is revealed in effectiveness studies, but critics who cling hard to their beliefs do not bend in the face of evidence that contradicts their point. In this sense, the issue becomes similar to political debates. People simply yell their claims more loudly and, because most individuals are not exposed to the results of scientific research, misunderstandings like this persist. If you are an individual suffering from a mental illness or know somebody else who is, be sure to make informed choices. Do not take anyone - myself included - at their word on the utility of a particular treatment. Instead, consult results like this and ask yourself whether the claims being made by clinicians are supported by any evidence. Sadly, the answer to that question is often "no."
Research is revealing a wealth of efficacious and effective treatments for mental illness. Each year, those treatments are refined or replaced by newer approaches with stronger results. This is, in fact, the beautiful dance of scientific progress, in which knowledge builds upon knowledge and competing ideas face off against one another with the results informing our next step. Sadly, there is a strong anti-science bias that, in combination with a lack of education on interpreting data and a poor effort to disseminate research findings, has resulted in an environment in which the very people trusted to provide mental health care often campaign against the tools we use to improve it. Psychotherapy Brown Bag hopes to contribute to the reversal of that trend.
If you would like to learn more about cognitive behavioral therapy for anxiety disorder, we recommend the following items and many others, all of which are available through our online store of scientifically-based psychological resources:
- Managing Social Anxiety: A Cognitive-Behavioral Therapy Approach Client Workbook
by Debra Hope, Richard Heimberg, Harlan Juster, and Cynthia Turk
- Managing Social Anxiety: A Cognitive-Behavioral Therapy Approach Therapist Guide
by Debra Hope, Richard Heimberg, and Cynthia Turk
-
Cognitive-Behavioral Therapy for Anxious Children: Therapist Manual, Third Edition
by Philip Kendall and Kristina Hedtke
- OCD in Children and Adolescents: A Cognitive-Behavioral Treatment Manual by John March and Karen Mulle Friesen
-
Treatment Plans and Interventions for Depression and Anxiety Disorders
by Robert Leahy
by Robert Leahy
- The Worry Cure: Seven Steps to Stop Worry from Stopping You
by Robert Leahy
- Generalized Anxiety Disorder: Advances in Research and Practice
by Richard Heimberg, Cynthia Turk, and Doug Mennin
Mike Anestis is a doctoral candidate in the clinical psychology department at Florida State University
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