Scientists at King’s College London have developed a blood test that
accurately and reliably predicts whether depressed patients will respond
to common antidepressants, which could herald a new era of personalised
treatment for people with depression.
Guided by this test,
patients with blood inflammation above a certain threshold could be
directed towards earlier access to more assertive antidepressant
strategies, such as a combination of antidepressants, before their
condition worsens.
Approximately half of all depressed patients
do not respond to first-line antidepressants and a third of patients are
resistant to all available pharmacological treatments. Until now, it
has been impossible to establish if individual patients will respond to
common antidepressants or if they need a more assertive antidepressant
treatment plan, which may include a combination of more than one
medication.
As a result, patients are treated with a
trial-and-error approach whereby one antidepressant is tried after
another, often for 12 or more weeks for every type of antidepressant.
This can result in long periods of ineffective antidepressant treatment
for individuals who may not show an improvement in symptoms anyway.
The study, published by The International Journal of Neuropsychopharmacology,
focused on two biomarkers that measure blood inflammation, as previous
studies have already shown that elevated levels of inflammation are
associated with poor response to antidepressants.
They measured the quantity of two biomarkers – of Macrophage Migration
Inhibitory Factor (MIF) and interleukin (IL)-1β- in two independent
clinical samples of depressed patients, before or after they took a
range of commonly prescribed antidepressants.
The researchers
found that blood test results above a specified threshold level could
precisely and reliably predict the probability of individuals responding
to the treatments. Patients with levels of MIF and IL-1βabove the
thresholds showed a 100 per cent chance of not responding to
conventional, commonly prescribed antidepressants. Those with
inflammation below the suggested threshold could be expected to respond
to first-line antidepressants, according to the study authors.
The
two biomarkers examined in the study are both thought to be important
in predicting how people with depression respond to antidepressants, as
they are involved in several brain mechanisms relevant to depression.
These include the birth of new brain cells and connections between them,
as well as the death of brain cells through a process called ‘oxidative
stress.’ Oxidative stress occurs when the body both overproduces and
then struggles to remove molecules called ‘free radicals.’ These free
radicals break down brain connections and disrupt the brain’s chemical
signalling, which in turn can lead to the development of depressive
symptoms by reducing the brain’s protective mechanisms.
Professor Carmine Pariante
from the Institute of Psychiatry, Psychology & Neuroscience (IoPPN)
at King’s College London and senior author of the study, said: ‘The
identification of biomarkers that predict treatment response is crucial
in reducing the social and economic burden of depression, and improving
quality of life of patients.
‘This study provides a
clinically-suitable approach for personalising antidepressant therapy –
patients who have blood inflammation above a certain threshold could be
directed toward earlier access to more assertive antidepressant
strategies, including the addition of other antidepressants or
anti-inflammatory drugs.’
Dr Annamaria Cattaneo,
first author from the IoPPN at King’s College London, said: ‘This is
the first time a blood test has been used to precisely predict, in two
independent clinical groups of depressed patients, the response to a
range of commonly prescribed antidepressants.
‘These results
also confirm and extend the mounting evidence that high levels of
inflammation induce a more severe form of depression, which is less
likely to respond to common antidepressants.’
Dr Cattaneo added:
‘This study moves us a step closer to providing personalised
antidepressant treatment at the earliest signs of depression.
‘It
is really crucial now to carry out a clinical study comparing the
current clinical practice in antidepressant prescription, based on
trial-and-error, with our novel approach of ‘personalised psychiatry’,
where the antidepressant treatment plan is guided by the blood test.’
