Does the Brain 'Remember' Antidepressants?

Photo: Brain

Individuals with MDD often undergo
multiple courses of antidepressant
treatment during their lives; © SXC

Individuals with MDD often undergo multiple courses of antidepressant treatment during their lives. This is because the disorder can recur despite treatment and because finding the right medication for a specific individual can take time.

Interestingly, the researchers used a harmless placebo as the key to tracking the footprints of prior antidepressant use.

Aimee Hunter, the study's lead author and an assistant professor of psychiatry at UCLA's Semel Institute for Neuroscience and Human Behaviour, and colleagues showed that a simple placebo pill, made to look like actual medication for depression, can "trick" the brain into responding in the same manner as the actual medication.

The investigators examined changes in brain function in 89 depressed persons during eight weeks of treatment, using either an antidepressant medication or a similar-looking placebo pill. They set out to compare the two treatments — medication versus placebo — but they also added a twist: They separately examined the data for subjects who had never previously taken an antidepressant and those who had.

The researchers focused on the prefrontal cortex, an area of the brain thought to be involved in planning complex cognitive behaviour, personality expression, decision-making and moderating social behaviour, all things depressed people wrestle with.

Brain changes were assessed using electroencephalograph (EEG) measures developed at UCLA by study co-authors Doctor Ian Cook, UCLA's Miller Family Professor of Psychiatry, and Doctor Andrew Leuchter, a professor of psychiatry and director of the Laboratory of Brain, Behaviour and Pharmacology at UCLA's Semel Institute. The EEG measure, recorded from scalp electrodes, is linked to blood flow in the cerebral cortex, which suggests the level of brain activity.

The antidepressant medication given during the study appeared to produce slight decreases in prefrontal brain activity, regardless of whether subjects had received prior antidepressant treatment during their lifetime or not. A decrease in brain activity is not necessarily a bad thing, the researchers note; with depression, too much activity in the brain can be as bad as too little.

However, the researchers observed striking differences in the power of placebo, depending on subjects' prior antidepressant use. Subjects who had never been treated with an antidepressant exhibited large increases in prefrontal brain activity during placebo treatment. But those who had used antidepressant medication in the past showed slight decreases in prefrontal activity — brain changes that were indistinguishable from those produced by the actual drug.; Source: University of California – Los Angeles