'Electric shock' depression therapy unravelled
Scientists have discovered how electroconvulsive therapy (ECT) works in people with severe depression, The Independent has reported.
During ECT, patients are anaesthetised and given a controlled electric current through the brain. But although ECT has been used to treat severe depression for decades, how or why it works has never been clear.
However, a new study has investigated this by performing brain scans on nine patients with severe depression before and after their ECT sessions. It found that, after treatment, the patients’ depression improved and there was a reduction in the connections in an area of the brain previously linked to both depression and cognitive function.
The main limitations to this study are its small size and the fact that it didn’t report what happened to patients who weren’t given ECT treatment. This means that it’s not possible to say what changes (if any) would have occurred over time to the patients not given ECT. However, it may be difficult to obtain a control group of similar people with severe depression who would not be offered ECT or an alternative treatment.
ECT is used by the NHS to treat severe cases of depression under specific circumstances and can have benefit for certain patients, although it can also have side effects. This type of research should help scientists to understand how it delivers its effects, and possibly develop other ways to achieve similar results with fewer side effects.
Where did the story come from?
The study was carried out by researchers from the University of Aberdeen and the University of Dundee, and was funded by the Chief Scientist Office of Scotland and the Scottish Funding Council. The study was published in the peer-reviewed journal, Proceedings of the National Academy of Sciences of the USA (PNAS).
The news sources have provided reasonable coverage of this study, although they do not discuss the lack of a control group receiving no ECT. Including a control group helps to establish a treatment’s effects as it allows researchers to see what patients experience when given a particular treatment and compare this with what happens when they are not.
There might be some difficulty in recruiting a control group who would not receive ECT, as the patients involved have severe depression that had not responded to other treatments such as medication. Therefore, not offering ECT might not be ethical.
What kind of research was this?
This was a before-and-after study looking at the effects of ECT on connections between nerve cells in the brain. The researchers say that previous studies have suggested that certain aspects of depression might be caused by increases in the connections between certain areas of the brain.
The researchers report that ECT has been used to treat severe depression for more than 70 years and that it is the most potent and rapidly acting antidepressant treatment for the condition. However, it does require administration of a general anaesthetic and is associated with side effects such as memory problems. The researchers also point out that we still do not fully understand how ECT works. They hoped that if they could understand how ECT has an effect, it might be possible to develop other ways to produce the same effect that would have fewer side effects and be less invasive.
As the study only looked at people who had ECT it isn’t possible to say what changes (if any) would have occurred in the brains of people not treated with ECT over the same time period.
What did the research involve?
The researchers studied nine adults who had been successfully treated for severe depression. They carried out brain scans of these patients before and after they received their treatment and then used special methods to analyse the scans to determine how “connected” each region of the brain was. The researchers were interested in areas where connections displayed changes after the ECT treatment, as these changes could be responsible for the beneficial effects seen after a course of ECT.
The participants in this study had severe depression that had not responded to drug treatment, and they had voluntarily accepted ECT. They received ECT twice a week until their doctors decided that they had recovered from their severe depression. This took an average of 8.3 treatments. Their level of depressive symptoms was assessed before ECT treatment, after the fourth session of treatment and at the end of the ECT treatment. The researchers did not target any specific areas of the brain in their analyses; they looked at the entire brain instead.
What were the basic results?
The researchers found that participants’ depressive symptoms improved significantly after ECT. Brain scans showed that after ECT there was also a decrease in the connections in an area called the “left dorsolateral prefrontal cortex”. This area of the brain has previously been linked to both depression and cognitive functioning, which the researchers thought might explain why efforts to achieve the benefits of ECT without adverse effects might not have been successful.
How did the researchers interpret the results?
The researchers concluded that their findings support the emerging idea that depression might be linked to having too high a level of connectivity in certain areas of the brain. They say that detecting this “hyperconnectivity” might be used as a way of identifing mood disorders, and that these connections could be a target for future treatments.
This small study has found a reduction in the connectivity of one area of the brain in patients who had received successful ECT treatment for severe depression. Previous research has shown that this area, the left dorsolateral prefrontal cortex, is implicated in both depression and cognition.
One limitation to the study is that it did not include a control group (patients not treated with ECT), therefore it is not possible to say what changes, if any, would have occurred in their brains. However, due to the severity of their depression, it may be difficult or unethical to obtain a control group of people who would not be offered ECT. Analysis of a larger number of patients receiving ECT would help to confirm these findings, particularly if such studies looked at whether the level of brain changes seen related to how much improvement a patient showed.
ECT has been used in the treatment of depression for a long time, and research such as this should help scientists to understand how it has its effects, and possibly develop other ways to deliver the same results. However, despite understanding better how ECT has its effects, developing new treatments based on this is likely to be a slow process.
The National Institute for Health and Clinical Excellence (NICE) guidance on depression in adults currently recommends that ECT should be considered for severe, life-threatening depression and when a rapid response is required, or when other treatments have failed. They say that ECT should not be routinely used for people with moderate depression but that it can be considered if their depression has not responded to other treatments. They recommend that the decision to use ECT should be made jointly with the patient if possible, and that the patient should be fully informed of the risks and benefits associated with having ECT. The risks they describe include the risks associated with the general anaesthetic needed for ECT and the possibility for side effects such as cognitive impairment (a deterioration in memory). However, this needs to be balanced with the risks associated with not receiving ECT.
- Perrina JS, Merzb S, Bennett DM et al. Electroconvulsive therapy reduces frontal cortical connectivity in severe depressive disorder. PNAS, March 19, 2012