Treatment-resistant depression: a critique of current approaches

Biological correlates of treatment resistant depression: a review of peripheral biomarkers

Introduction

Many patients fail to respond to multiple antidepressant interventions, being defined as "treatment-resistant depression" (TRD) patients. TRD is usually associated with increased severity and chronicity of symptoms, increased risk of comorbidity, and higher suicide rates, which make the clinical management challenging. Efforts to distinguish between TRD patients and those who will respond to treatment have been unfruitful so far. Several studies have tried to identify the biological, psychopathological, and psychosocial correlates of depression, with particular attention to the inflammatory system. In this paper we aim to review available studies assessing the full range of biomarkers in TRD patients in order to reshape TRD definition and improve its diagnosis, treatment, and prognosis.

Methods

We searched the most relevant medical databases and included studies reporting original data on possible biomarkers of TRD. The keywords "treatment resistant depression" or "TRD" matched with "biomarker," "inflammation," "hormone," "cytokine" or "biological marker" were entered in PubMed, ISI Web of Knowledge and SCOPUS databases. Articles were included if they included a comparison with healthy controls (HC).

Results

Of the 1878 papers identified, 35 were included in the present study. Higher plasma levels of IL-6 and TNF-α were detected in TRD patients compared to HC. While only a few studies on cortisol have been found, four papers showed elevated levels of C-reactive protein among these patients and four articles focused on immunological cells. Altered kynurenine metabolism in TRD patients was reported in two studies, while contrasting results were found with regard to BDNF.

Conclusion

Only a few biological alterations correlate with TRD. TNF-α seems to be the most relevant biomarker to discriminate TRD patients from both HC and treatment-responsive MDD patients. Moreover, several discrepancies among studies have been found, due to methodological differences and the lack of a standardized diagnostic definition of TRD.

Treatment resistant opioid use disorder (TROUD): Definition, rationale, and recommendations

The opioid overdose epidemic kills about 130 people a day in the United States and it is estimated that there are about 2.1 million people who suffer from an opioid use disorder (OUD). Academic neuroscientists, psychiatrists and the National Institute of Drug Abuse have spent the last forty-years establishing the foundation of addiction as a brain disorder. It is now clear that extended opioid use causes multiple important and at times, irreversible changes to the brain, especially to its dopamine and opioid systems. With our recognized criteria for diagnosis and the accepted multifaceted treatment approach of both professional psychotherapy and medications that assist treatments, treatment failures should be limited. Unfortunately, this is not the case. Slips, relapses, overdose and multiple failures are all too common. Similar to treatment resistant depression there is a subpopulation who do not respond to standard OUD treatments. However, the field has suggested that if a treatment does not work, it is either the patients fault, they have not hit bottom or simply we need to try the same treatment again. There is a rational to consider this a new category of OUD, treatment resistant opioid use disorder (TROUD). This paper explores past treatment attempts data from OUD patients entering traditional outpatient treatment and makes recommendations how TROUD can be defined. It challenges the addiction research and treatment providers to change its focus from individuals being resistant to the unique conditions associated with this brain disorder as being resistant to treatment as usual.

Treatment-resistant depression: resistant to definition?

OBJECTIVE

To better define treatment-resistant depression (TRD) so as to assist clinical management and refine treatment guidelines.

METHOD

In this study, we examine a broad range of clinical variables in depressed patients (n=196) referred to a tertiary referral Mood Disorders Unit (MDU). Information was collected from patients, referrers and assessors over a period of 32 months and included evaluations of treatments, treatment resistance and related variables. Data were analysed across trichotomized 'high', 'low' and 'no' treatment resistance groupings of patients.

RESULTS

A significantly greater proportion of patients with melancholia were amongst the high TRD group, and this was consistent across different strategies for evaluating melancholia.

CONCLUSION

Melancholia perhaps provides a prototypic TRD subset that perhaps reflects some innate aspects of melancholic depression or factors such as the impact of ageing. Research into TRD is needed to both replicate this finding and perhaps explicate it further.

Therapeutic alternatives for difficult-to-treat depression: a narrative review of the state of the evidence

Despite the large number of depressed patients who do not respond to first-line antidepressants, the evidence base of alternate strategies is quite thin. In this article, a simple 5-stage system for categorizing treatment-resistant depression (TRD) is described and the evidence pertaining to the major strategies currently utilized is summarized using four grades, ranging from D (case reports only) to A (multiple positive placebo-controlled trials). It is concluded that the level of evidence supporting many of the contemporary strategies used for TRD (eg, combinations of antidepressants and augmentation with medications such as pindolol, buspirone, or modafinil) is scanty at best. Even the fundamental question concerning "to augment or to switch" is not answerable with available data. It is noted that the best-documented treatments (ie, lithium augmentation, switching to a monoamine oxidase inhibitor, and electroconvulsive therapy) are among the least utilized. This state of affairs will improve with completion of the studies of Systematic Treatment Alternatives to Relieve Depression, a large multicenter study of difficult-to-treat depression funded by the National Institute of Mental Health. There is a need for greater collaboration among academicians and organizations, such as the American Psychiatric Association, the National Institute of Mental Health, and the pharmaceutical industry, to ensure that sufficient research is conducted so that clinician's choices for patients with TRD can be guided by empirical evidence.

Characteristics, treatment patterns, and outcomes of persistent depression despite treatment in primary care

We examine the sociodemographic and clinical characteristics of depressed primary care patients who receive at least minimal standards of evidence-based treatment, comparing those who remain depressed with those who recover; and their subsequent treatment patterns and other outcomes. We used observational data from a subset of 542 treated patients participating in a group-level randomized controlled trial of quality improvement interventions for depression conducted in six managed care organizations. Nonresponse to treatment was defined as having at least minimally appropriate treatment for at least two of three 6-month periods but continuing to have probable depression. Our definitions of depression and appropriate treatment are broader than those used in clinical trials, but relevant to primary care settings. Many of the factors predictive of treatment resistance in clinical trials predict nonresponse to guideline concordant care among diverse primary care, depressed patients. The main unique predictors of nonresponse to treatment include a clinical factor (suicide ideation) requiring clinician assessment and intervention, a social/economic factor (unemployment) usually not addressed by medical interventions, and medication nonadherence. Nonresponders used more adjunctive therapies and combination medications, suggesting clinicians and patients were searching for solutions. High rates of service use and poor outcomes emphasize the urgency of new research to find solutions for these patients.

Economic implications of treatment-resistant depression among employees

BACKGROUND

Conservative estimates indicate between 10% and 20% of all individuals with major depressive disorders (MDDs) fail to respond to conventional antidepressant therapies. Amongst those with MDD, individuals with treatment-resistant depression (TRD) have been found to be frequent users of healthcare services and to incur significantly greater costs than those without TRD. Given the prevalence of the disorder, it is understandable that MDDs are responsible for a significant amount of both direct and indirect healthcare costs.

OBJECTIVE

To provide empirical findings for employees likely to have TRD based on analysis of employer claims data, in the context of previous research.

METHODS

We conducted a claims data analysis of employees of a large national (US) employer. The data source consisted of medical, pharmaceutical and disability claims from a Fortune 100 manufacturer for the years 1996-1998 (total beneficiaries >100000). The employee sample included individuals with medical or disability claims for MDDs (n = 1692). A treatment pattern algorithm was applied to classify MDD patients into TRD-likely (n = 180) and TRD-unlikely groups. Treated prevalence of select comorbid conditions and the patient costs (direct and indirect) from the employer perspective by condition were compared among TRD-likely and TRD-unlikely employees, and with a 10% random sample of the overall employee population for 1998.

RESULTS

The average annual cost of employees considered TRD-likely was dollars US 14490 per employee, while the cost for depressed but TRD-unlikely employees was dollars US 6665 per employee, and dollars US 4043 for the employee from the random sample. TRD beneficiaries used more than twice as many medical services compared with TRD-unlikely patients, and incurred significantly greater work loss costs.

CONCLUSION

TRD has gained increasing recognition due to both the clinical challenges and economic burdens associated with the condition. TRD imposes a significant economic burden on an employer. TRD-likely employees are more likely to be treated for selected comorbid conditions and have higher medical and work loss costs across all conditions.

Venlafaxine and treatment-resistant depression

Treatment-resistant depression (TRD) is an important clinical problem. This paper briefly reviews the definition of TRD and summarizes methodological issues that pertain to treatment research. Recent studies of venlafaxine treatment for TRD also are reviewed. It is concluded that venlafaxine at higher doses is a reasonably well-tolerated and an effective alternative for patients with TRD and typically should be used before tricyclic antidepressants or monoamine oxidase inhibitors. Further research is needed to confirm the prediction that switching a SSRI nonresponder to venlafaxine is a more effective strategy than switching to a second SSRI. The relative merits of switching from a SSRI to venlafaxine versus adding a norepinephrine reuptake inhibitor also warrant careful study.

Sustained response to open-label venlafaxine in drug-resistant major depression

The aim of this study was to evaluate the response to venlafaxine in patients with treatment-resistant depression during an extension phase of an open-label study of venlafaxine. After completing the initial 8 weeks of the study, patients could continue venlafaxine treatment for an additional period of up to 10 months. Efficacy results are given for 149 patients with treatment-resistant depression. Response was defined as a 50% reduction in scores on the Montgomery-Asberg Depression Rating Scale (MADRS); 69% were responders after 8 weeks of treatment in the initial study phase, and 73% were responders at their final extension-phase visit. The mean MADRS score was 32.8 before treatment, 12.9 by 8 weeks, and 10.8 at the final extension visit. There was a statistically significant reduction of 2.1 MADRS units from entry into the extension phase to the final extension visit. At extension entry, 36.7% patients were in remission, as defined by a MADRS score of less than 12, whereas at the final extension visit, this had increased to 49%. Improvement in Clinical Global Impressions Scale scores (both patient and physician ratings) was maintained throughout the extension period, with 88% of patients reporting some improvement (75% with "very much" or "much") and 92% of doctors noting some improvement in patients (79% with "very much" or "much") at the last extension visit. The safety profile during the extension phase of the study was similar to that found in the initial phase and in other studies. The most common study events were somnolence (21%), headache (18%), insomnia (16%), sweating (16%), constipation (14%), dry mouth (11%), nausea (10%), and dizziness (10%). Patients with resistant depression that was treated with venlafaxine maintained their response for up to 10 months after an 8-week phase of treatment and showed some evidence of further improvement.

Short-term spontaneous improvement rates in depressed outpatients

The objectives of the present report were: a) to determine the spontaneous remission rate in depressed outpatients who do not receive antidepressant medication; b) to develop a novel method for obtaining a control group that can be used to gauge the effectiveness of antidepressant medication in clinical practice; and c) to compare response rates from the present sample with outcomes of depressed patients in our practice who were treated with antidepressant medications. By using a naturalistic design, prospective assessments were made on all depressed outpatients. Twenty-five patients who met full criteria for a major depressive episode ended up not taking antidepressant medication for a variety of reasons. "Response" rates to a no-treatment trial were determined with standard outcome criteria using the Clinical Global Impression-Improvement scale. Eight patients (32.0%) had a positive response, 5 patients (20.0%) had a partial response, and 12 patients (48.0%) were nonresponders to a no-treatment trial. These response rates were higher than expected, but significantly lower than what we had found in a cohort of depressed patients who underwent an antidepressant trial (p = .02). Likewise, treatment-resistant patients fared better on pharmacotherapy, though this difference was not statistically significant. These results suggest that the occurrence of spontaneous remissions may be common in clinical practice, and therefore the specific short-term benefits of antidepressant medication in clinical practice may frequently be overestimated. Despite the high rate of spontaneous remission in our sample, the present study allowed us to confirm the effectiveness of antidepressant medication in clinical practice using a novel method for obtaining a control comparison group.

A review of the use of augmentation therapy for the treatment of resistant depression: implications for the clinician

OBJECTIVE

To critically review the literature on augmentation therapy in resistant depression in order to assist the clinician to make a reasoned choice. Augmentation therapy is defined as the addition of a second agent to an existing antidepressant regimen with the aim of achieving improved clinical response.

METHOD

The available literature which related specifically to currently popular augmentation strategies in treatment resistant depression for the past 20 years was examined. The scientific evidence supporting the efficacy of these regimens and their safety was reviewed.

RESULTS

Considerable research on lithium augmentation has been undertaken, and on triiodothyronine augmentation to a lesser degree. A number of other drugs have been trialed as augmentation agents with claims of success; however, most of the evidence supporting these agents is anecdotal and in the form of case reports. There are very few well-performed double-blind placebo-controlled studies of augmentation therapy.

CONCLUSIONS

Because of possible complex pharmacodynamic and pharmacokinetic interactions, augmentation therapy is not without its potential complications. Lithium augmentation of tricyclic antidepressants can be recommended as a safe and effective strategy and there is a body of scientific evidence supporting the addition of T3 as an effective augmentation agent. Recent research with pindolol augmentation of selective serotonin re-uptake inhibitors (SSRIs) is encouraging, but these findings require replication. There is no empirical evidence supporting buspirone, carbamazepine, sodium valproate, methylphenidate or amphetamine as effective augmentation agents, or that adding a tricyclic to a SSRI has usefulness in relieving depressive symptoms. There is a need for considerable research in this area, with more prospective well-controlled placebo studies.

Definition and epidemiology of treatment-resistant depression

Our results suggest that between 29% and 46% of depressed patients fail to respond fully with antidepressant treatment of adequate dose and duration. In particular, although partial response appears to occur in 12% to 15% of the depressed patients studied, nonresponse is observed in 19% to 34% of this population. The prevalence of treatment-resistant depression derived from studies using ITT analysis is likely to be an overestimate of the actual occurrence of the phenomenon, as these rates also reflect the outcome of patients who were treated inadequately or were intolerant to the treatment. On the other hand, data derived from studies using completer analysis are likely to generate under-estimates of the prevalence of this phenomenon, as patients may have dropped out before completion of the study due to lack of efficacy. One could, therefore, guess that the actual rates of treatment resistance in the clinical population of depressed patients probably lie between these two types of estimates. From an epidemiologic point of view, because the prevalence of depression has been estimated to vary from 2.6% to 5.5% in men and from 6.0% to 11.8% in women, one must conclude that treatment-resistant depression is a very common clinical problem that is likely to affect more than one third of depressed patients. In summary, treatment-resistant depression patients can be defined as those who fail to respond to standard doses (i.e., significantly superior to placebo in double-blind studies) of antidepressants administered continuously for at least 6 weeks. Additional requirements of this operational definition are an accurate diagnosis of depressive disorder, patient compliance with the treatment, the use of valid outcome measures, and therapeutic range of antidepressant blood levels for the tricyclic antidepressants. Finally, symptomatic improvement that is equal or greater than 25% and less than 50% qualifies as partial response, and less than 25% symptomatic improvement is complete nonresponse.

Management of treatment-resistant unipolar and chronically depressed patients

The majority of depressed patients presenting as treatment refractory will respond to a properly chosen new medication or to a previous agent administered correctly. Drug combinations are less frequently required than current practice would indicate, and their usage depends at present more on clinical experience than scientific fact. Educating the patient about the series of options available, and the sequence in which they will be undertaken, and imbuing the enterprise with hopeful optimism are essential ingredients to ultimate success.

Clinical and subclinical hypothyroidism in patients with chronic and treatment-resistant depression

OBJECTIVE

To investigate the relationship between hypothyroidism and treatment-resistant depression (TRD).

METHOD

A retrospective case audit of 93 inpatients of a specialist Mood Disorders Unit. Patients referred with TRD were sub-classified into 'adequate' or 'inadequate' prior treatment groups on the basis of pre-established criteria, and compared with a 'non-TRD' control sample. Grades I (clinical) and II (subclinical) hypothyroidism were determined by review of relevant thyroid indices.

RESULTS

Patients had chronic depressive disorders (sub-group means of 57.5-82.2 weeks of illness). Of those patients referred with TRD, 22% (10/46) had evidence of clinical or subclinical hypothyroidism compared with 2% (1/47) of the non-TRD patients (p < 0.01). A gradient in the rates of grade I hypothyroidism was observed with the adequately-treated TRD patients having the highest rate (13%), the inadequately-treated TRD patients having an intermediate rate (7%), and the non-TRD patients having the lowest rate (2%). Consistent with this view, the inadequately-treated TRD group had the highest rate of grade II hypothyroidism (p = 0.01) and tended to have higher thyroid stimulating hormone (TSH) values (p = 0.06). Differences in the rates of hypothyroidism could not be accounted for by differences in age or prior exposure to lithium and/or carbamazepine. Duration of the depressive episode was negatively correlated with both the free thyroxine indices (r = -0.25, P < 0.05) and TSH levels (r = -0.32, p < 0.01).

CONCLUSIONS

This study suggests that relative hypothyroidism may play a role in the development of some treatment-resistant depressive disorders.