Subtle investigator bias resulting from dichotomous thinking about mental health interventions is but one complicating factor that has led to com bined treatments being understudied. Another factor that has significantly influenced research patterns has been the quest to identify, with increasing specificity, "cures" for mental disorders. This search represents something of a conundrum, which can be outlined in broad strokes as follows: Psychological distress is a heterogeneous and nonspecific concept, and its experience is unique to each sufferer. One can define, albeit in rather nebulous terms, some of the features that separate one form of psychological distress from another, but it remains true that most people with schizophrenia, or most depressed patients, share in common only the most obvious features of their diagnoses. Nevertheless, the aim of much of mental health research in the past 50 years has been to search for increasingly specific remedies. We are therefore placed in the awkward position of positing molecular cures for molar concepts that are heterogeneous, nonspecific, and experienced in an absolutely unique manner by each sufferer.
The past 50 years of mental health research has led to the successful development of many specific pharmacological and psychological treatments that have improved patient outcomes (Michels, 1999). At least in the short term, specific pharmacological interventions do assist many patients in coping with the more disabling aspects of their illness, sometimes dramatically so. Yet there is also evidence that these increasingly specific results do not translate into lasting improvement. Rates of successful treatment for schizophrenia have not appreciably changed in the past 100 years (Hegarty, Baldessarini, Tohen, Waternaux, & Oepen, 1994), despite the synthesis of effective antipsychotic drugs. New-generation antidepressants, such as the serotonin reuptake inhibitors, have not resulted in improved long-term remission rates, neither have increasingly specific psychological treatments. In the well-known (if not overstudied) Treatment of Depression Collaborative Research Project (Elkin et al., 1989), recovery rates at 18-month follow-up did not differ among any treatment. Recovery ranged from 19% for clinical management plus imipramine to 30% for cognitive-behavior therapy (CBT; Jacobson & Hollon, 1996), a less-than-splendid showing for any treatment. To a large extent, then, specificity and success do not correlate well.
Paradoxically enough, increasing the specificity of treatment has constrained our ability to perform certain types of research. Because one can demonstrate the success of specific treatments in short-term (although rarely in long-term) outcome studies, we have greater difficulty justifying the application of combined treatments. Essentially, the issue is the ability to justify a more complex, possibly more expensive treatment when simpler and cheaper remedies have been shown to be of utility. Is it ethical to impose unproven, costlier combinations on patients when less complicated alternatives, already shown to be of value, exist? This question is subject to considerable debate and arises in numerous examples throughout this chapter.
The issue of specificity pertains to diagnoses as well as treatment. It is a grave error to assume that, once having made a Diagnostic and Statistical Manual of Mental Disorders—type (DSM) diagnosis, the treatment becomes uniform. Hohagen et al. (1998) demonstrated, for example, that patients with DSM-I1I-R (American Psychiatric Association, 1987) obsessive—compulsive disorder (OCD) did best with unimodal therapy (behavioral treatment) if their symptoms were primarily compulsive but did best with combined medication and behavior treatment if their symptoms were primarily obsessive. Along similar lines, Wells and Sturm (1996) found that addition of minor tranquilizers to antidepressant therapy did nothing to improve outcomes in the treatment of major depressive disorder. Yet it is clear that a subset of patients with major depression present with significant anxiety symptoms. When these symptoms are appropriately managed with a short-term course of benzodiazepines, outcome is improved (Buysse et al., 1997; Smith, Londborg, Glaudin, & Painter, 1998).
This introduction should remind the reader that in spite of the high prevalence of combined treatment in clinical practice our knowledge of combined treatments is poor. They may not work as well as single-modality treatments for some disorders; they may provide more rapid or lasting relief in others. Because combined treatments are often not supported by the current literature, clinicians should be circumspect in devising such treatments for their patients. At the same time, clinicians should be careful to balance the needs of individual patients against the results of large-scale studies or meta-analyses, for these are poor predictors of individual response in the clinical setting (cf. Klein, 1998). For most conditions, single-modality treatments should be attempted before combined treatments are implemented and, for all conditions for which it has found to be effective, psychosocial treatment should be included in the treatment plan.
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