Deep brain stimulation may prove a viable treatment option for patients with treatment-resistant depression, according to a study co-authored by Paul Holtzheimer, a psychiatrist at Dartmouth-Hitchcock Medical Center. Holtzheimer collaborated with researchers at the Emory University School of Medicine to investigate the effects of DBS on both major depressive disorder and bipolar II disorder.
To execute the study which could improve the rate at which patients are rehabilitated researchers first defined treatment-resistance in patients as the "failure of adequate yet present treatment for the current [depressive] episode," Hotzheimer said.
Through a surgical procedure, DBS electrodes were implanted into patients' brains and wires were tunneled under the skin through the neck into the chest wall, according to the study. The wires were connected to an implanted pulse generator, comparable to a pacemaker, inside the region located above the breast and below the collarbone, Hotzheimer said.
"Brain stimulation requires a neurosurgical procedure," Holtzheimer said. "It's an extraordinarily, at least in the terms of psychiatry, invasive procedure."
Following the procedures, patients exhibited decreased levels of depression. The number of patients in remission and responding to treatment increased significantly, he said.
According to the study, 18 percent of patients experienced remission and 41 percent responded to treatment in the first 24 weeks. After one year, 58 percent of patients were in remission, while 92 percent showed some form of improvement.
The strategy employed by the researchers is new in the field of psychiatry, stemming from a related procedure known as electroconvulsive therapy. Since 1938, ECT has been an effective substitute for antidepressant medication when patients have proven unresponsive to antidepressants, according to Gus Dixon, a psychiatrist at the Mental Health Association in Long Beach, Calif.
Unlike ECT, which is administered periodically in a medical clinic, the DBS procedure continuously impacts the patient after an initial surgery.
"There is no treatment which is more powerful at normalizing patients' brain function than ECT and deep brain stimulation is similarly effective," Dixon said. "I don't choose [ECT] as first treatment, but ECT will work when normal medicines have not worked."
Practices for treating depression since the 1950s have focused on regulating the levels of the neurotransmitters serotonin, norepinephrine and dopamine, Hotzheimer said. The new method instead focuses on stimulating specific areas of the brain associated with various neuropsychiatric disorders.
For most patients with depression, prescribed antidepressants act as inhibitors that increase the available quantities of these neurotransmitters and adequately treat the condition, according to Dixon. Patients who are treatment-resistant to antidepressants are often administered generic medications like lithium or thyroid hormone, which are unspecific to depression, Holtzheimer said.
Despite the initial success of DBS, the research is inconclusive on the effects of DBS on serotonin, norepinephrine and dopamine levels.
"These patients probably have a depression that is driven by something else, and that's the way we approach it now," Holtzheimer said.
