Most classes of antidepressant medications, including the selective serotonin reuptake inhibitors (SSRIs), are thought to require 2 or more weeks of use before therapeutic effects become noticeable. The consumer guidelines for a drug like Celexa (citalopram) clearly advise patients not to expect immediate benefits but to continue taking their medication as prescribed. However, a recent study has cast doubt on the notion that SSRIs really take weeks to build up to therapeutic levels. If the results are confirmed with subsequent experiments, then our understanding of these medications will be greatly enhanced. Observing the neurochemical mechanism behind specific SSRIs will naturally lead to more beneficial prescribing patterns and better patient outcomes.
In a study of the SSRI Celexa, 26 participants were given either a single dose of the drug or a dose of placebo, a harmless sugar pill. None of the participants had depression, a fact which allowed researchers to study specific physiologic responses without interference. Three hours later, participants were shown images of frightened faces while brain activity in their amygdala was measured via magnetic resonance imaging. Psychiatrists have theorized that hyperactivity in the amygdala is a measurable effect of depression that places the individual in a constant state of heightened anxiety. In the single-dose Celexa study, participants given medication showed a muted response in their amygdala when viewing frightened or anxious faces. Researchers observed a spike in amygdala activity in those who received placebo. These findings demonstrate that potentially therapeutic effects begin as quickly as a few hours after the first dose of Celexa, and by extension any SSRI. Interestingly, none of the participants reported either a change in mood or unusual side effects. The study authors theorize that the action on the amygdala has both immediate benefits on an unconscious level and longer term effects on anxiety.
Depression is often described as a constellation of symptoms and effects. Because of its many manifestations, the disease is a long way from being fully understood. There is currently no fool-proof, one-size-fits-all treatment for depression. Research on antidepressant medications like Celexa helps us identify what’s happening in the depressed brain. Armed with that knowledge, we can tailor more effective medications in the future. The study under discussion, for example, highlights the possibility that Celexa’s beneficial effects begin with the amygdala, the brain’s primitive fear center. More importantly, these effects begin almost immediately, contrary to previous assumptions.
Murphy, S., Norbury, R., O’Sullivan, U., Cowen, P., Harmer, C. (2009). Effect of a single dose of citalopram on amygdala response to emotional faces. British Journal of Psychiatry, 194(6), 535-540.
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