Neuroimaging of Mood Disorders

Although significant advances have been made in the treatment of mood disorders, how to individualize treatment is still not understood. Diagnoses in psychiatry are based on symptoms rather than on the causes of the disorder; thus, treatment decisions are based on choosing an intervention that works in patients with a particular group of symptoms and not necessarily on the pathology specific to an individual patient. This is not necessarily a problem except that a substantial percentage of patients with mood disorders do not achieve remission, even with optimal treatment.^1,2 In fact, complete symptom remission is rare and recurrences are frequent-finding a successful treatment often takes multiple trials of various drugs.

During repeated attempts at finding successful treatment or during recurrences, patients may become demoralized, lose hope, and discontinue treatment. Prolonged mood symptoms increase the suffering, the morbidity and, potentially, the mortality associated with these disorders. An objective method to predict and understand treatment outcome is needed.³ In most clinical scenarios, the question is not whether the patient has a mood disorder but rather which treatment, if any, is most likely to enable the patient to achieve wellness.

Neuroimaging technologies

CT, MRI, diffusion tensor imaging (DTI), functional MRI (fMRI), magnetic resonance spectroscopy, positron emission tomography (PET), single photon emission CT (SPECT), and functional near-infrared spectroscopy (fNIRS) offer a noninvasive way to investigate the neurobiology associated with mood disorders. Unfortunately, because there are no neuropathological criteria that define mood disorders, no criteria exist to compare directly with neuroimaging findings. Thus, the neurobiology to be examined has to be defined in other ways.

One method by which neuroimaging could potentially help in clinical decision making would be to increase our understanding of the brain correlates of treatment. Identifying the neurobiology that can be used to predict a patient’s response to a particular treatment, as well as what changes occur with a successful treatment, would have profound clinical and scientific implications. A number of different strategies have been used to understand the brain characteristics that predict response and that correlate with successful outcome. (For a more detailed coverage of the literature, reviews of research using neuroimaging in mood disorders from several perspectives are available.^4-8)

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