Using Botox to stay young might have a previously unsuspected side effect - depression.
Psychologists have warned that using the procedure to smooth lines around the mouth means you can't smile properly, leading to depression.
The research, at the University of Cardiff, shows just how important using our facial expressions is, not only to indicate to others how we feel, but also to influence our own mood.
Though it goes in and out of fashion, Botox is still one of the most popular cosmetic treatments. Psychologist Dr Michael Lewis, who led this study, has also investigated how Botox affects people who have it done on other areas of the face.
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Those who had Botox on their forehead were less able to frown and consequently had improved mood. Dr Lewis has suggested Botox may be able to help people with OCD and other disorders by preventing expressions such as disgust, which influence our feelings.
Dr Lewis explained: "The expressions we make on our faces affect the emotions we feel. We smile because we are happy but smiling also makes us happy."
"Treatment with drugs like Botox prevents the patient from being able to make a particular expression.
"For example, those treated for frown lines with Botox are not able to frown as strongly. This interrupts the feedback they would normally get from their face and they feel less sad."
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If you're going to have Botox, it seems your forehead is the best target to make you feel as good as you look. But Dr Lewis warns that there is some evidence to suggest that you can be more gullible after this procedure as you're unable to raise your eyebrows in surprise or scepticism.
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