People who experience high levels of anxiety
could benefit from a single high dose of a common antidepressant
that has been shown to reduce anxiety within three hours.
Dr Susannah Murphy, a neuroscientist at the
Psychopharmacology and Emotion Research Laboratory at the
University of Oxford, has conducted a study looking at the impact
of two antidepressants, citalopram and reboxetine, which
respectively work on the serotonin and noradrenaline
neurotransmitters in the brain that control mood. She presented her
findings at the Royal College of Psychiatrists’ International
Congress in Edinburgh.
The study involved giving 42 healthy patients
either one of the two drugs, or a placebo, then showing them a
picture with two faces on it – one with a neutral expression and
the other looking fearful. Researchers then measured the speed with
which the volunteers reacted to the images.
Anxiety is linked to ‘hypervigilance’, and the faster the reaction
the more anxious and concerned about a perceived threat a person
is. Dr Murphy and her colleagues found that both citalopram and
reboxetine reduced their vigilance to fearful facial expressions.
The antidepressants could be used both in the short- and long-term
to enhance psychological therapies, such as cognitive behavioural
therapy, she told to delegates at the International Congress.
Curious about the impact of antidepressants on
the brain, Dr Murphy gave 26 healthy volunteers a single 20mg dose
of citalopram and three hours later scanned their brains while the
participants completed the facial expression task. She found that
the amygdala, a chestnut-sized structure buried deep in the brain
and linked to processing emotions and reading emotions in others,
showed high levels of activity.
Citalopram and reboxetine belong to a group of
antidepressants known as Selective Serotonin Reuptake Inhibitors
(SSRIs). These are conventionally believed to have a delay of
several weeks before the onset of their therapeutic effects – but
Dr Murphy’s study shows clearly that doses can have a neurochemical
effect within hours.
She told delegates: “It’s quite extraordinary
that these changes take place so early. It really challenges us to
think quite differently about the way antidepressants work. It’s a
different message for patients – as soon as you start taking the
drugs it starts changing the way the brain works. It doesn’t have
to take weeks.
“When you are anxious you are hypervigilant to
the social signals that people give off and you can interpret them
negatively. For instance, at the end of a presentation or talk, if
someone stands up and asks you a question and they look at you -
are they looking at you in a positive or a negative way? All of
that feeds into your reaction.”
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International Congress of the Royal College of Psychiatrists, Edinburgh, 21-24 June 2010