Predicting who will respond to a particular treatment for depression

by Michael D. Anestis, M.S.

Recently, I wrote an article in which I described the evidence that variations of cognitive-behavioral therapy and interpersonal psychotherapy perform as well as or better than antidepressant medication in the treatment of depression.  In the most recent issue of the Journal of Consulting and Clinical Psychology, Jay Fournier and colleagues (2009) published a study that elevated this conversation to another level.  In this particular study, the authors expanded upon the question of "which approach to treatment is more successful in reducing symptoms of depression" by asking "which individuals are most likely to respond to treatment and, of those, who will respond better to which treatment?"  These types of questions - those that allow us to better understand who the best candidates are for particular types of therapy - are pivotal targets for research if we are to develop an effective system of mental health care that adequately treats the broadest possible spectrum of individuals.

As an empiricist, I am very much in favor of comparative treatment research - studies that systematically test whether one therapeutic approach outperforms another in the treatment of a particular mental illness.  Such studies allow us to develop a hierarchy of treatments based upon objective results, thereby increasing our ability to quickly treat individuals presenting with mental illness.  This is, in fact, the basis for the empirically supported treatment (EST) movement.  At the same time, it is important to acknowledge that some individuals simply will not respond to the best available treatment.  Similarly, for mental illnesses such as depression for which there are several ESTs, none of which stands out as definitively superior to the others, clinicians are left without a clear guideline with respect to determining the best approach for a particular individual. 

Here is where research like the Fournier et al. (2009) study is so valuable.  The authors conducted a randomized controlled study examining individual responses to antidepressant medication and cognitive therapy for moderate to severe depression.  The sample was comprised of individuals seeking outpatient care for depression and included 60 individuals randomly assigned to receive cognitive therapy and 120 individuals randomly assigned to receive antidepressant treatment, with treatment lasting 16 weeks.

The first question the authors sought to answer was which variables predicted whether an individual was likely to respond to either treatment.  In other words, the authors were not examining which treatment performed better, but rather, which individuals were likely to show the expected benefits of treatment and which individuals were likely not to respond.  Their results indicated that individuals with a history of chronic depression, individuals who were older, and individuals with lower levels of intelligence were less likely to respond to cognitive therapy or antidepressants.  Importantly, this does not mean that such individuals are doomed to a poor response to either of these treatments.  It simply means that, on average, such individuals are less likely to respond.  In fact, other reviews have found that neither age nor intelligence significantly predicted depression treatment outcome (e.g., Dunkin et al., 2000; Hirschfeld, et al., 1998; Petersen, et al., 2002) As Fournier and colleagues (2009) suggest, this finding means that such individuals might be ideal targets for alternative treatment approaches.  Such approaches could include simultaneous cognitive therapy and antidepressant use, interpersonal psychotherapy, or an alternative approach with less empirical support.

The second question the authors sought to answer was which individuals were more likely to respond to cognitive therapy versus antidepressants.  In other words, the authors wanted to see whether particular characteristics of individuals could help predict the likelihood that they would exhibit a positive response to a specific treatment.  Here again, the data offered some interesting insights.  Individuals who were married or cohabiting, unemployed, or had experienced a significant number of recent negative life events (e.g., fired from a job, financial crisis, breakup from a relationship) were more likely to respond well to cognitive therapy than to antidepressants.  Here again, some caution is required in interpreting the results.  The fact that married individuals fair better in cognitive therapy does not mean that unmarried individuals or individuals not cohabiting fair better with antidepressants.  The results indicated that unmarried individuals and individuals not cohabiting were equally likely to benefit from one treatment versus the other.  The same thing goes for employment status and the number of recent negative life events.  Additionally, being married does not guarantee a positive response to cognitive therapy or a negative response to antidepressants.  It simply adjust the odds of responding to one treatment versus another. 

It is extremely important that we keep in mind that this is simply one study.  In order to have complete confidence that a particular variable (e.g., marital status) will impact an individual's response to a particular treatment, the same finding must be reliably and independently replicated by other research teams.  As the authors themselves noted, the work of Fournier and colleagues (2009) thus serves as a wonderful foundation for future work, not the final conclusion for a long-standing debate.  Hopefully other researchers will conduct equally well designed studies on this topic in the near future and offer us more insight into which individuals respond well to front line treatments for depression and, of those who do, which individuals are best served by which empirically supported treatments.

If you would like to learn more about empirically supported treatments for depression, we recommend the following resources, all of which are available through our online store:

• Cognitive Therapy of Depression - by Aaron Beck, M.D.

• Cognitive Therapy Techniques: A Practitioner's Guide - by Robert Leahy, Ph.D.

• Treatment Plans and Interventions for Depression and Anxiety Disorders - by Robert Leahy, Ph.D.

• Practicing Cognitive Therapy: A Guide to Interventions (New Directions in Cognitive-Behavior Therapy) - by Robert Leahy, Ph.D.

• Roadblocks in Cognitive-Behavioral Therapy: Transforming Challenges into Opportunities for Change - by Robert Leahy, Ph.D.
  

• Clinician's Quick Guide to Interpersonal Psychotherapy - by Myrna Weissman, Ph.D.
  

• Comprehensive Guide To Interpersonal Psychotherapy - by Myrna Weissman, Ph.D.
  

• Treatment for Chronic Depression: Cognitive Behavioral Analysis System of Psychotherapy (CBASP) - by James McCullough, Ph.D.
  

• Patient's Manual for CBASP - by James McCullough, Ph.D.
  

• Treating Chronic Depression with Disciplined Personal Involvement: Cognitive Behavioral Analysis System of Psychotherapy (CBASP) - by James McCullough, Ph.D.
  

• Mindfulness-Based Cognitive Therapy for Depression: A New Approach to Preventing Relapse - by Zindel Segal, Ph.D.

Mike Anestis is a doctoral candidate in the clinical psychology department at Florida State University