A study in mice offers clues to why treatments of fear and other mood disorders that combine both medication and psychological treatments are often the most effective ones. It also offers clues to how drugs like Prozac work.
Psychological treatments for conditions like fear, anxiety and PTSD often bring some relief. But over time, the fear and anxiety begin to come back of their own accord, a phenomenon psychologists call spontaneous recovery. It's as if the fearful memories were weakened but never quite eliminated and eventually re-assert themselves. This study, though it was in mice, suggests that antidepressants may help extinguish these painful memories for good.
Fear is one of the most basic emotions and is common to nearly all creatures. And this particular study is of a phenomenon well-documented in humans.
They seem to do this by returning certain brain cells to a younger, more plastic state, where new learning can replace the older, fearful lessons of the past. But the medication alone isn't enough. It has to be accompanied by behavioral or psychological treatment for the new learning to sink in.
In the study, adult mice were trained to fear a tone by repeatedly giving them a foot shock right after the tone was produced. After two weeks of this, some of the mice were given fear extinction therapy--repeated exposure to the tone without an accompanying foot shock, while others were not. And half of the mice had their drinking water replaced by a Prozac solution.
The mice were then tested at various time periods to see how the behavioral therapy and the drug therapy, alone and in combination, affected their fear of the tone, by looking at whether or not the mice froze when they heard the tone.
The basic results were that both the Prozac and fear extinction training lessened the recovery of fear as time passed. But the combination of the two treatments was much more successful at preventing the return of fear when mouse heard the tone.
The researchers also found physical changes in specific groups of neurons involved in fear memory circuitry in Prozac treated mice, particularly in the amygdala, indicating that these neurons had been returned a more plastic state closer to that seen in young mice. Previous experiments have shown that fear extinction in young mice tends to be much more permanent than that in adult mice.
But fear is one of the most basic emotions and is common to nearly all creatures. And this particular study is of a phenomenon well documented in humans. Many studies have shown that various mood disorders, from phobias to depression, respond best when treated with a combination of medication and behavioral therapy. This study may explain some of the neurophysiology behind that observation.
An article on the study appears in Science.