A new treatment for depression is under study, and if the results are as promising as hoped, it will be a viable alternative for patients who do not respond well to conventional treatments.

Anti-depressants and other medications, as well as psychotherapy, are usually prescribed for clinical depression. (The condition is diagnosed when feelings of sadness or unhappiness overwhelm and affect normal, healthy life over a prolonged period.)

When these don’t work and depression spirals into deeper feelings of guilt or worthlessness, electroconvulsive therapy (ECT) might be given.

But because ECT involves putting the patient under general anaesthesia and inducing a seizure, the researchers are hoping that transcranial direct current stimulation (tDCS) will prove to be a safer and more tolerable alternative.

tDCS treatment involves running an electric current through two electrodes placed on either side of the patient’s head. “The current used in tDCS is very small, about 1-3mA (milliampere, a measure of electric current), compared to the almost 800mA used in ECT,” said Dr Chan Herng Nieng, Consultant, Department of Psychiatry, Singapore General Hospital (SGH).

In Singapore, an ordinary 60-watt light bulb uses about 0.25A, or 250mA. “In depression, the left side of the brain or the left dorsolateral prefrontal cortex seems to be hypoactive or not as active, while the right seems to be overactive. So the left electrode tries to increase activity on the left, and the right, to down-regulate or reduce activity,” added Dr Chan.

He is the Principal Investigator of the study, a collaboration between SGH and the National University Hospital (NUH). Other members of the team include Dr Johnson Fam, Consultant, Department of Psychological Medicine, NUH, and Dr Poon Shi Hui, Registrar, Department of Psychiatry, SGH. Dr Fam is NUH Site Principal Investigator, while Dr Poon is Co-Investigator.

This is the first clinical trial in Singapore to study the use of tDCS in treating depression, but at least four studies elsewhere, in Italy, Germany, Australia and the US, have found tDCS to be effective in treating depression.

tDCS drew interest in the 1960s when studies found that direct stimulation affected brain function. It is undergoing a revival currently, with researchers looking at its use in various conditions, including migraine, chronic pain and Parkinson disease. The local team aims to recruit 20 patients who suffer from moderate to severe depression.

Each tDCS treatment session lasts about 30 minutes, although participants will spend about 1½ hours at the hospital each time. The full course of treatment consists of 20 to 30 daily weekday sessions. Participants might feel a tingling sensation when the tDCS is being administered, and experience some redness after the electrodes are removed.

With ECT, some patients experience temporary amnesia after treatment. ECT treatments are administered two to three times a week, with each course of treatment comprising six to 12 sessions.

Although very safe, ECT poses some risks, such as those associated with general anaesthesia. For this reason, although effective, ECT is not recommended unless the patient cannot tolerate or is not responding to drugs or therapy, and is highly depressed or suicidal.

Even with the current standard treatments, depression recurs. Studies elsewhere have found that just 30 per cent to 50 per cent of patients achieve remission, meaning they no longer have depressive symptoms.

For those reasons, the aim of the tDCS study, said Dr Fam, “is for the treatment to be a viable alternative to ECT”.

Balancing the right and the left

In depression, the left and right dorsolateral prefrontal cortices, located at the front of the brain, are found to be underactive and hyperactive respectively. tDCS aims to restore this imbalance by passing a very weak current for 30 minutes from the anode (positive electrode) placed on the left to the cathode (negative electrode) on the right of the head. The patient is alert and sitting still during the session.

In Singapore, depression afflicts 5.8 per cent of adults at some point in their lives, according to a Singapore Mental Health Study conducted in 2010.

When sadness doesn’t go away

Depression is a feeling of sadness that is so persistent and prolonged that it starts to affect a person’s ability to work and have normal healthy social relationships.

Other symptoms include having difficulty sleeping, poor appetite and energy levels so low that one often does not want to get out of bed. People with depression might also move or talk more slowly. They often complain that they have difficulty making decisions or concentrating.

“What we really worry about is when they start to have very excessive feelings of guilt, or feelings of worthlessness, sometimes to the point of thinking of ending their lives,” said Dr Chan Herng Nieng, Consultant, Department of Psychiatry, Singapore General Hospital.

If the various symptoms persist for two weeks or more, the patient is considered to be suffering from clinical depression.

Ref. Q15