First reliable biomarker in psychiatry
In a statement from the UK nonprofit Science Media Centre, Vladimir Litvak, PhD, with the Wellcome Centre for Human Neuroimaging, University College London, said that the study is interesting, noting that it is from “one of the leading groups in the field.”
The fact that depression symptoms can be treated in some patients by electrical stimulation of the ventral striatum is not new, Dr. Litvak said. However, what is “exciting” is that the authors identified a particular neural activity pattern in the amygdala as a reliable predictor of both symptom severity and stimulation effectiveness, he noted.
“Patterns of brain activity correlated with disease symptoms when testing over a large group of patients are commonly discovered. But there are just a handful of examples of patterns that are reliable enough to be predictive on a short time scale in a single patient,” said Dr. Litvak, who was not associated with the research.
“Furthermore, to my knowledge, this is the first example of such a reliable biomarker for psychiatric symptoms. The other examples were all for neurological disorders such as Parkinson’s disease, dystonia, and epilepsy,” he added.
He cautioned that this is a single case, but “if reproduced in additional patients, it will bring at least some psychiatric conditions into the domain of brain diseases that can be characterized and diagnosed objectively rather than based on symptoms alone.”
Dr. Litvak pointed out two other critical aspects of the study: the use of exploratory recordings and stimulation to determine the most effective treatment strategy, and the use of a closed-loop device that stimulates only when detecting the amygdala biomarker.
“It is hard to say based on this single case how important these will be in the future. There is no comparison to constant stimulation that might have worked as well because the implanted device used in the study is not suitable for that,” Dr. Litvak said.
It should also be noted that implanting multiple depth electrodes at different brain sites is a “traumatic invasive procedure only reserved to date for severe cases of drug-resistant epilepsy,” he said. “Furthermore, it only allows [researchers] to test a small number of candidate sites, so it relies heavily on prior knowledge.
“Once clinicians know better what to look for, it might be possible to avoid this procedure altogether by using noninvasive methods,” such as functional MRI or EEG, to match the right treatment option to a patient, Dr. Litvak concluded.
The research was funded by the National Institutes of Health, the Brain & Behavior Research Foundation, and the Ray and Dagmar Dolby Family Fund through the department of psychiatry at UCSF. Dr. Scangos has reported no relevant financial relationships. A complete list of author disclosures is available in the original article. Dr. Litvak is participating in a research funding application to search for electrophysiological biomarkers of depression symptoms using invasive recordings.
A version of this article first appeared on Medscape.com.