One-third of patients suffering from depression do not respond to antidepressants, and of those who do, only about half recover completely. Now, researchers think they are beginning to understand why.
"How antidepressants work and why they do so for some and not others remains a bit of a mystery," said Ned Kalin, chair of the psychiatry department at the University of Wisconsin Madison. However, using functional magnetic resonance imaging (fMRI) - a technique that takes snapshots of the working brain - Dr Kalin and his team believe they can predict which patients will benefit most from using antidepressants.
In a study published in the American Journal of Psychiatry , the researchers used fMRI to monitor the brain activity of 12 depressed patients who were shown a random assortment of scenes known to elicit positive or negative emotions. This was conducted before treatment, and repeated at two and eight weeks after taking the antidepressant venlafaxine (Effexor).
They found that depressed patients showing more activity in the anterior cingulate (part of the brain concerned with focusing attention, which is activated when people face conflict) before treatment responded better to the medication than those with lower pre-treatment activity. The team is looking at whether these results are specific to Effexor or whether they are common to other antidepressants.
Dr Kalin hopes that by using fMRI, which is widely available, sufferers will have a "higher hit rating with the drugs in future".
Marjory Wallace, chief executive of the mental health charity Sane, told The THES : "Being able to predict whether the medication will be effective could save critical time when patients are suffering from their worst depression."