Page last updated at 00:37 GMT, Monday, 26 October 2009
Antidepressants 'work instantly'
By Michelle Roberts
Health reporter, BBC News
The drugs appear to promote positive thinking
Antidepressants get to work immediately to lift mood, contrary to current belief, UK researchers say.
Although patients may not notice the effects until months into the therapy, the team say they work subconsciously.
The action is rapid, beginning within hours of taking the drugs, and changes negative thoughts, according to the Oxford University researchers.
These subtle, positive cues may add up over time to lift the depression, the American Journal of Psychiatry reports.
It may also explain why talking therapies designed to break negative thought cycles can also help.
We found the antidepressants target the negative thoughts before the patient is aware of any change in feeling subjectively
Lead researcher Dr Harmer
Psychiatrist Dr Catherine Harmer and her team at Oxford University closely studied the reactions of 33 depressed patients and 31 healthy controls given either an antidepressant or a dummy drug.
The depressed patients who took the active drug showed positive improvements in three specific measures within three hours of taking them.
These patients were more likely to think about themselves in a positive light, rather than dwelling on their bad points, the researchers said.
They were also more likely to see the positive in others.
For example, if they saw a grumpy person they no longer internalised this to think that they must have done something wrong to upset the person.
This was despite feeling no improvement in mood or anxiety.
Dr Harmer said: "We found the antidepressants target the negative thoughts before the patient is aware of any change in feeling subjectively.
"Over time, this will affect our mood and how we feel because we are receiving more positive information."
She said the findings could help scientists looking for new drugs to treat depression.
Dr Michael Thase, a psychiatrist from the University of Pennsylvania, said the findings challenged conventional wisdoms and were potentially "paradigm-changing".
But he said much more research was needed.
"The highest research priority is to confirm that the rapid effects observed in this study are predictive of eventual clinical benefit."
He said it was possible that switching off the negative thoughts was a crucial part of the therapy.
Alternatively, it might merely be a sign that the drug was beginning to work at the cell level in the brain.
Paul Farmer, chief executive of Mind, said: "This research may contribute to our understanding of how our bodies respond to antidepressants, but the changes recorded can't always be felt by patients and it can be some weeks before they begin to feel the symptoms of depression easing.
"We must also remember that the side-effects of medication can often be felt straight away long before the benefits really kick in, and this will always affect people's experiences in the initial stages of treatment."
Am J Psychiatry 2009; 166:1178-1184
(published online September 15, 2009; doi: 10.1176/appi.ajp.2009.09020149)
(c) 2009 American Psychiatric Association
Effect of Acute Antidepressant Administration on Negative Affective Bias in Depressed Patients
Catherine J. Harmer, D.Phil., Ursula O’Sullivan, M.B.Ch.B., F.R.A.N.Z.C.P., Elisa Favaron, M.D., Rachel Massey-Chase, B.A., Rachael Ayres, B.A., Andrea Reinecke, Dipl.Psych., Dr.rer.nat., Guy M. Goodwin, D.Phil., F.R.C.Psych., and Philip J. Cowen, M.D., F.R.C.Psych.
OBJECTIVE: Acute administration of an antidepressant increases positive affective processing in healthy volunteers, an effect that may be relevant to the therapeutic actions of these medications. The authors investigated whether this effect is apparent in depressed patients early in treatment, prior to changes in mood and symptoms. METHOD: In a double-blind, placebo-controlled, between-groups randomized design, the authors examined the effect of a single 4-mg dose of the norepinephrine reuptake inhibitor reboxetine on emotional processing. Thirty-three depressed patients were recruited through primary care clinics and the community and matched to 31 healthy comparison subjects. Three hours after dosing, participants were given a battery of emotional processing tasks comprising facial expression recognition, emotional categorization, and memory. Ratings of mood, anxiety, and side effects were also obtained before and after treatment. RESULTS: Depressed patients who received placebo showed reduced recognition of positive facial expressions, decreased speed in responding to positive self-relevant personality adjectives, and reduced memory for this positive information compared to healthy volunteers receiving placebo. However, this effect was reversed in patients who received a single dose of reboxetine, despite the absence of changes in subjective ratings of mood or anxiety. CONCLUSIONS: Antidepressant drug administration modulates emotional processing in depressed patients very early in treatment, before changes occur in mood and symptoms. This effect may ameliorate the negative biases in information processing that characterize mood and anxiety disorders. It also suggests a mechanism of action compatible with cognitive theories of depression.
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