While we all must admit to our ups and downs, for most people moods are but a manageable filter between us and the world, a tint in the mind. It's quite different for patients with bipolar disorder, who skid uncontrollably through the spectrum of normal human emotions. And one side of the mood disorder, severe depression, looms like a pool of quicksand. Many patients who wade into this psychic sludge stay permanently, resistant to all conventional forms of therapy.
Although still extremely experimental, deep brain stimulation is emerging as a therapy of last resort for sufferers of bipolar disorder and a new study in the Archives of General Psychiatry shows that bipolar patients who use stimulators may become less depressed the longer they stick with it.
Psychiatrists at Emory University in Atlanta implanted deep brain stimulators in 17 patients whose symptoms of depression persisted after attempts to treat them with drug and electroconvulsive therapies. The device consists of a set of electrodes patched onto both sides of the brain at the subcallosal cingulate. A pulse generator implanted high up in the patient's chest connects to the electrodes, providing chronic activation to a region of the brain targeted in many antidepressant therapies.
They put one in each patient and then they fiddled with it.
They left it off for a month. Then turned it on for a month. Then turned it back off in some cases to see what would happen, all without the patients ever knowing what treatment they were receiving. After a month of stimulation, the patients began to show lessened signs of depression when measured on the Hamilton Depression Rating Scale, with average scores dropping 43 percent. When the researchers turned off the device in three patients, symptoms peaked again and the results were severe enough that they decided it was unethical to impose the same interruption on the rest of the group. For the following two years, the researchers provided continuous stimulation.
"What we saw was that the response definitely increased over time," said Paul Holtzheimer, a lead author on the study (in an audio interview available here). And so, patients that weren't well at six months were likely to be better at one year and were likely to be even better at two years."
The results confirm similar observations made a few years ago by psychiatrist Helen Mayberg, another author on the study. However, this is the first study to show that deep brain stimulation can safely treat bipolar disorder (specifically looking at patients with a bipolar-2 diagnosis). There was some concern that by pulling patients out of depression the therapy might catapult them back into a manic episode.
Not all of the study participants were bipolar, but none of those who were lapsed into mania. "That's an important aspect of treatment in this group because if a treatment works for the depression but causes mania or hypo-mania then it's not really an effective treatment," said Holtzheimer.
Despite the encouraging results, Holtzheimer has described the approach as "very much experimental" and acknowledged that a large test group will be needed in the future.
The study also brings up one potential concern in the logistics of treating depressive patients with an electronic device. When doctors interrupted treatment, the depressive symptoms eventually returned. Worse, it took longer for them to subside once the stimulator was turned back on, as though the patients had finally gotten up their hopes for true relief only to be let down once again. In this scenario the patients didn't know that the device had been turned off, whereas in a real world situation they would know how the stimulator was operating. But it does suggest that depressive patients would be particularly sensitive to a sudden interruption in treatment, caused, say, by a failing battery. The batteries that the researchers at Emory used last about 2 years, just long enough for their study,
In hearing aids, a drained battery may not be the end of the world. In a disorder where suicide is a possible end game, backups will have to be in place.