The theories

Because scientists don't understand the metabolism of depression, they can't understand why ECT relieves it. But current theories revolve around how the therapy affects two kinds of brain chemicals.

- Neurotransmitters. Scientists believe that depression is caused by the malfunction in the chemical messengers called neurotransmitters that regulate emotion and mood - serotonin, dopamine, neurepinephrine and others. One theory is that ECT causes neurotransmitters to flood the brain, temporarily bringing their levels back to normal, or another theory speculates that it changes the way brain cells receive the neurotransmitters.

- Neuroendocrine. Just as neurotransmitters are believed to affect mood and emotion, so do some hormones. One theory is that ECT affects the function of the hypothalamus, a gland deep in the brain that, among other things, releases chemicals that affect mood.

In 46 A.D., Scribonius Largus, a physician to the Roman emperor Claudius, discovered that the torpedo fish, also known as the electric ray, cured headaches. Scientists later learned that the fish stuns its prey by producing small pulses of electricity in its muscles.

An illustration from the 1871 book "A Practical Treatise on the Medical and Surgical Uses of Electricity'' depicts a procedure known as the electric hand. The doctor conducts electricity through himself and into the patient suffering from nervous exhaustion.

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