August 12, 2011

Antidepressants' Boomerang Effect

For all the good they do, antidepressants may lead to another bout of depression. Here's why, according to a large review.

People who treat depression by taking antidepressants are more likely to experience future bouts of depression than those who use no medication at all. This is the conclusion of a recent analysis of nearly 40 years of published research.

The Meta-Analysis found that patients with major depressive disorder who did not take medication for it had a 25% risk of relapse, while patients who took antidepressants and eventually stopped taking them had a 42% risk of relapse.

This suggests that antidepressants can leave people stuck in a cycle where they have to continue taking the drug for an unknown number of years to prevent a return of symptoms. They're not a short-term solution for depression.

Andrews cites the relapse rates as evidence that the brain pushes back, attempting to restore the level of these neurotransmitters to their pre-medication level.

Dr. Paul Andrews, an evolutionary psychologist at McMaster University, headed the research team. The team looked at 46 papers published as far back as 1974 that studied the treatment of 3,454 patients with major depressive disorder. They compared the relapse rate of patients who took only Placebo in the various studies to those who had taken an antidepressant and were later switched to placebo. Those who took antidepressants were over two-thirds more likely to suffer a relapse. The stronger the antidepressant, the higher was the rate of relapse.

Antidepressants alter brain chemistry, changing the level of neurotransmitters such as serotonin and norepinephrine. Andrews cites the relapse rates as evidence that the brain pushes back, attempting to restore the level of these neurotransmitters to their pre-medication level. This is similar to what occurs when people take pain medication and it causes the pain medication to be steadily less effective over time. When people stop taking antidepressants, the brain continues to push back and overcompensates, causing too large a change in neurotransmitter level. This can trigger a new episode of depression. In essence, antidepressants cause a boomerang effect once they're discontinued.

Andrews compares taking antidepressants to placing a weight on a spring. When antidepressants are discontinued, the weight is removed and the spring shoots out beyond it's normal resting length, before eventually returning to it. This overshoot can cause a new bout of depression.

Andrews hypothesizes that changes in brain chemistry are frequently a symptom of depression, not a cause, much as fever is a symptom of a bacterial infection. And just as trying to cure a bacterial infection by treating fever symptoms is usually inappropriate, trying to cure depression by altering brain chemistry may very well be a counterproductive approach.

Not everyone agrees with this hypothesis. The exact causes of depression are not currently known and how depression should be treated is a highly controversial topic with many different viewpoints.

An article on the analysis was published in the July 2011 issue of Frontiers in Psychology.

Paul W. Andrews, PhD, is an Assistant Professor in the Department of Psychology, Neuroscience & Behaviour at McMaster University in Ontario.

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