The theory that depression is caused by a chemical imbalance is often presented in the media as fact even though there is little scientific evidence to support it, according to a new study co-authored by a Florida State University visiting lecturer.

Jeffrey Lacasse, an FSU doctoral candidate and visiting lecturer in the College of Social Work, and Jonathan Leo, a neuroanatomy professor at Lincoln Memorial University in Tennessee, found that reporters who included statements in news articles about depression being caused by a chemical imbalance, or a lack of serotonin in the brain, were unable to provide scientific evidence to support those statements.

Lacasse and Leo spent about a year in late 2006 and 2007 monitoring the daily news for articles that included statements about chemical imbalances and contacting the authors to request evidence that supported their statements. Several reporters, psychiatrists and a drug company responded to the researchers' requests, but Lacasse and Leo said they did not provide documentation that supported the chemical imbalance theory. Their findings were published in the journal Society.

"The media's presentation of the theory as fact is troublesome because it misrepresents the current status of the theory," Lacasse said. "For instance, there are few scientists who will rise to its defense, and some prominent psychiatrists publicly acknowledge that the serotonin hypothesis is more metaphor than fact. As the current study documents, when asked for evidence, reporters were unable to cite peer-reviewed primary articles in support of the theory."

Moreover, the researchers said, several of the responses received from reporters seem to suggest a fundamental misunderstanding of the theory's scientific status. The "Diagnostic and Statistical Manual of Mental Disorders," which almost all psychiatrists use to diagnose and treat their patients, clearly states that the cause of depression and anxiety is unknown, according to Lacasse and Leo.

The Society article builds on the pair's 2005 study, which focused on pharmaceutical advertisements that claim depression is caused by an imbalance of serotonin -- an imbalance the drug companies say can be corrected by a class of antidepressants called Selective Serotonin Reuptake Inhibitors (SSRIs).

"The chemical imbalance theory, which was formulated in the 1960s, was based on the observation that mood could be artificially altered with drugs, rather than direct observation of any chemical imbalances," Leo said. "Since then there has been no direct evidence to confirm the theory and a significant number of findings cast doubt on the theory."

The researchers said the popularity of the theory is in large part based on the presumed efficacy of the SSRIs, but they say that several large studies now cast doubt on this efficacy. A review of a full set of trial data published in the journal PLoS (Public Library of Science) Medicine last month concluded that much of the perceived efficacy of several of the most common SSRIs was due to the placebo effect. Other studies indicate that for every 10 people who take an SSRI, only one to two people are truly receiving benefit from the medication, according to Lacasse and Leo.

Still, the National Center for Health Statistics found that antidepressants are the most prescribed drugs in the United States, with doctors writing more than 31 million prescriptions in 2005. Both Lacasse and Leo emphasized the importance of patients being given factual information so they can make informed decisions about medications and the role of other potentially useful interventions, such as psychotherapy, exercise or self-help strategies.

"Patients might make different choices about the use of medications and possibly use alternative approaches to their distress if they were fully informed," Lacasse said. "We believe the media can play a positive role by ensuring that their mental health reporting is congruent with scientific literature."

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Source: Jeffrey Lacasse
Florida State University