BMJ: Long
term use of antidepressants is associated with a sustained increase in
risk of weight gain over at least five years, finds a study published in
The BMJ today. The
findings show that patients prescribed any of the 12 most commonly used
antidepressants were more likely to experience weight gain than those
not taking the drugs. The risk was greatest during the second and third
years of treatment.
Obesity
and weight gain are global public health problems, with approximately
60% of UK adults currently overweight or obese. Depression is common in
people who are severely obese and the rate of antidepressant prescribing
is increasing, which could have potential impact on public health.
However, little research has been reported on the impact of widespread antidepressant treatment on weight gain.
So
a UK based research team, led by Rafael Gafoor at King’s College
London, set out to investigate the association between the use of
antidepressants and weight gain.
The
researchers analysed body weight and body mass measurement data from
the UK Clinical Practice Research Datalink (CPRD) for over 300,000
adults with an average age of 51, whose body mass index (BMI) had been
recorded three or more times during GP consultations from 2004-2014.
Participants
were grouped according to their BMI (from normal weight to severely
obese) and whether or not they had been prescribed an antidepressant in a
given year. Participants were then monitored for a total of 10 years.
The
researchers found that the absolute risk of gaining at least 5% weight
without antidepressant use was 8.1 per 100 person years; whereas the
risk with antidepressant use was 9.8 per 100 person years.
To
put this into context, this means that for every 59 people taking
antidepressants, one extra person would gain at least 5% weight over the
study period.
The
risk was greatest during the second and third years of treatment.
During the second year of treatment, the risk of gaining at least 5%
weight was 46% higher than in the general population, but no association
was found during the first 12 months of treatment.
They
also found that people who were initially of normal weight had a higher
risk of moving to either the overweight or obese groups, and people who
were initially overweight had a higher risk of moving to the obese
group if they were taking antidepressants.
Results
remained largely unchanged after further analysis to take account of
various factors including age, sex and whether the participants had
other conditions such as diabetes, stroke and cancer.
This is an observational study, so no firm conclusions can be drawn
about cause and effect, and the researchers outline some limitations
that could have affected the results. However, strengths include the
large number of participants and long term follow up.
The
researchers say that the results suggest the widespread use of
antidepressants “may be contributing to long term increased weight gain
at a population level, and that the potential for weight gain should be
considered when antidepressant treatment is indicated.”
Lead author Dr Rafael Gafoor from King’s College London, said: “It’s
important to stress that no patients should stop taking their medication
and that if they have any concerns they should speak with their doctor
or pharmacist.”*
In
a linked editorial, Alessandro Serretti and Stefano Porcelli, from the
University of Bologna emphasise that doctors should give lifestyle
advice on diet and exercise to minimise the risk of gaining weight and
that weight should be measured during antidepressant treatment.
They
say that whilst antidepressant treatment should always be offered to
those with moderate or severe depression, alternative treatment such as
group cognitive behavioural therapy may be preferable for people with
milder depression.
“Currently,
we are still unable to identify patients at higher risk of weight gain
with antidepressants. Hopefully it will be possible in the not too
distant future to identify a genetic predisposition and recognise those
at higher risk before treatment is started”, the authors conclude.
[Ends]
*Free quote; not found in text
Editorial: Antidepressant induced weight gain
Journal: The BMJ