A well-known side effect of Botox is the incapability to fully express feelings. Now, a new study has disclosed another side effect of the anti-wrinkle jabs: the incapacity to fully feel emotions.

The injection successfully 'freezes' the facial muscles around wrinkles, smoothing the skin but suppressing facial expressions.

A study showed that those given the toxin injections had significantly less reaction to emotionally charged films as compared to who had not had the treatment.

The study supports the psychological theory that facial expressions can have an effect on your mood, as well as being an indicator of it - so, for example, not being able to smile means you do not feel as happy.

Researcher Joshua Davis said, "With the advent of Botox, it is now possible to work with people who have a temporary, reversible paralysis in muscles that are involved in facial expressions."

"The muscle paralysis allows us to isolate the effects of facial expression and the subsequent sensory feedback to the brain. With Botox, a person can respond otherwise normally to an emotional event, for example a sad movie, but will have less movement in the facial muscles that have been injected, and therefore less feedback to the brain. It thus allows for a test of whether facial expressions and the sensory feedback from them can influence our emotions," Davis added.

The results of the study have been released in the academic journal Emotions. (With Inputs from Agencies)