Researchers may have uncovered a biomarker to signal when a patient with schizophrenia may be resistant to antipsychotic drugs, a common barrier to developing effective, timely treatments. The findings are published in the American Journal of Psychiatry. [1]
Patients who respond well to antipsychotics show an increased level of dopamine function in the brain whereas nonresponders do not. However, measuring the dopamine response is complicated, as there are currently no definitive imaging markers that show on MR scans of the brain. A research team led by Marieke van der Pluijm, PhD from the Amsterdam University Medical Center, turned to Neuromelanin-sensitive MRI (NM-MRI), which measures dopamine function, to see if a marker could be found in nonresponders.
“Increased NM-MRI signal has been shown in psychosis, but has not yet been assessed in nonresponders,” van der Pluijm and the authors wrote.
For their study, NM-MRI scans from 79 patients suffering from their first-episode of psychosis were treated, all of whom were assessed again during a six-month followup to measure the response in their brains. A voxel-wise analysis was conducted within the substantia nigra prior to treatment, examining the correlation between NM-MRI signal and patients' response to their treatment. These results were measured against a healthy control group of 20.
The analysis revealed 297 significant voxels in the ventral tier of the substantia nigra that were associated with nonresponse to treatment. From the cohort, 15 patients were classified as nonresponders, and 17 were excluded because of a lack of medication adherence or a change in their diagnosis.
Of the remaining 47, their NM-MRI signals matched the control group, with a lower-level of signals suggesting they responded positively to treatment. NM-MRI signal separated nonresponders from responders with areas under the curve between 0.62 and 0.85. Additionally, none of the NM-MRI signals from the entire cohort changed between the initial scan and the six-month followup.
“These findings provide further evidence for dopaminergic differences between medication responders and nonresponders and support the potential of NM-MRI as a clinically applicable marker for treatment resistance in schizophrenia,” the authors wrote.
Given the small scale of the study, more research is necessary to confirm these findings. Additional research is also necessary to discover better treatments for nonresponders. However, the use of this marker could ultimately lead to more rapid treatment for patients with schizophrenia.
The full study is available at the link below.
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