Treating Depression in Primary Care: Are Biomarkers the Key?

Charles P. Vega, MD


November 06, 2014

In This Article

Can a Lab Test Guide Antidepressant Therapy?

Depression is one of the world's most common chronic illnesses, and it remains undertreated despite large-scale efforts to change physicians' practices. Part of the difficulty in treating depression is due to confusion over which antidepressant to prescribe to an individual patient.

A new study[1] finds differential treatment effects of two antidepressants, based on patients' baseline serum levels of C-reactive protein (CRP). This important finding may pave the way for the use of biomarkers in the management of depression. However, that time has not yet come. For now, the clinician needs to balance adverse events and small differential effects in terms of therapeutic efficacy in making a choice between different antidepressants.

Depression: Unmet Needs

Depression continues to be one of the important chronic medical conditions worldwide. In an analysis of data from 14 different countries, the overall prevalence of depression in the developed world was 17.9%, which compared unfavorably with the rate of depression in the developing world (9.4%).[2] The lifetime prevalence of mood disorders in the United States specifically is approximately 20%.[3]

And these are not just cases of "the blues." Over one half of cases of depression in the United States are rated as severe or very severe.[4] Three quarters of adults with depression have other comorbid mental health diagnoses, and 40% of persons with a substance use disorder have a concomitant mood disorder. Also, depression is associated with worse control of chronic medical conditions, such as diabetes.[5,6] Finally, a study of survey data from 183,100 participants in the National Survey on Drug Use and Health found that the prevalence of suicidal ideation among adults with depression was 26.3%.[7]

Despite the high prevalence and severe consequences of depression, it remains underrecognized and undertreated. In a study of over 1600 patients with depression in The Netherlands, the rate of undertreatment of moderate or severe major depressive disorder was 43%.[8] Among patients seen only in primary care practices, this rate was 73%.

Part of the difficulty of treating depression noted in this study and in routine practice is the choice of antidepressant therapy. An analysis of medical decision-making in the treatment of depression demonstrated that physicians' personal beliefs were at least as important as patient-related variables in the choice to initiate an antidepressant.[9] Specifically, physicians' history of personally receiving treatment for depression and their beliefs regarding the overprescription of antidepressant medications were some of the most significant factors when choosing to write a prescription.

More objective criteria could help better personalize treatment for depression. The study by Uher and colleagues[1] evaluates an interesting hypothesis: Could a commonly available and simple laboratory test measuring systemic inflammation help predict response to antidepressant treatment?


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