several markers related to different parts of a pathway could be far more useful. Some of these markers may not be genetic—they may be “downstream markers” such as protein or metabolite levels in cells or the blood, or imaging of active brain regions. For example, imaging of a region of the brain known as “area 25” has revealed that it is overly active before treatment for depression and less active after treatment. This is the case whether the treatment consists of medication, cognitive-behavioral therapy, or even placebo. Conversely, in those who do not respond to an intervention, activity in this area does not decrease. This decrease in activity in area 25 thus appears to be necessary, and possibly sufficient, for the antidepressant response. Perhaps by combining a better understanding of brain circuitry from imaging with genetic and proteomic data, a panel of diverse biomarkers could be developed that would predict responses.
NIH supports research to discover potential biomarkers using a variety of approaches. The development and use of biomarkers can contribute to what Insel called the 3D pathway, which stands for discovery, development, and dissemination. Once potential indicators of clinical response or toxicity have been identified, these predictors need to be studied through prospective development studies. Finally, predictors need to be cost-effective so that they will be adopted and change the standard of care. Too often, powerful evidence-based interventions are neglected in medical practice because they either are not reimbursed or are not well understood.
Insel noted that, while biomarkers could have an enormous impact on the prevention, diagnosis, and treatment of mental illness, their benefits and costs need to be carefully weighed. The emphasis today is on making health care more efficient and less expensive, not more high-tech and more expensive.
FDA (Food and Drug Administration). 2004. Innovation or stagnation: Challenges and opportunity on the critical path to new medical products. http://www.fda.gov/oc/initiatives/criticalpath/whitepaper.html (accessed October 17, 2008).
FDA. 2005. Guidance for industry: Pharmacogenomic data submissions. http://www.fda.gov/downloads/RegulatoryInformation/Guidances/UCM126957.pdf (accessed October 17, 2008).
Frantz, S. 2004. FDA publishes analysis of the pipeline problem. Nature Reviews Drug Discovery 3:379.
Insel, T. 2008. Biomarkers for psychiatric drug toxicity. Speaker presentation at the Institute of Medicine Workshop on Assessing and Accelerating Development of Biomarkers for Drug Safety, October 24, Washington, DC.
WHO (World Health Organization). 2002. The world health report 2002: Reducing risks, promoting healthy life. Geneva, Switzerland: WHO.