US researchers suggest that people who have undergone Botox treatments not only change their appearance but may also have a weakened ability to experience emotions.

Joshua Davis from Columbia University in New York wrote about their findings in a paper published online in the journal Emotions this month.  Although it has been over a century since William James, an American pioneer of psychology proposed a theory of emotion that stated unless it can be expressed physically in the body it doesn't really exist, nowadays referred to as the facial feedback hypothesis (FFH), attempts to test it have been inconclusive.

That is until Botox (and presumably Dysport) came along, because it paralyzes face muscles used to express emotion (thus reducing wrinkles) and so you can use it to test FFH by comparing its effect with that of a cosmetic filler that does not affect facial muscles: this is essentially what the researchers did.

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," Davis reports. 

A person who has received treatment with Botox can respond to an emotional event, for instance a sad scene in a movie, but their facial muscles will be less active, and this sends less feedback to the brain about what the face is expressing.

It thus allows for a test of whether facial expressions and the sensory feedback from them to the brain can influence our emotions," explained Davis who said Botox enabled them to design a study where they could "isolate the effects of facial expression and the subsequent sensory feedback to the brain that would follow from other factors, such as intentions relating to one's expressions and motor commands to make an expression".

For the study, Davis examined two groups of participants: one received Botox treatment and the other, the control group, received Restylane, a cosmetic filler that does not paralyze facial muscles.The participants filled in questionnaires about their emotional experiences to watching positive and negative video clips before and after treatment.

The researchers wrote that results from the Botox group showed no changes between the pre- and post-treatment emotional responses to the most positive and negative video clips, but when they compared the two groups they found that the Botox group showed an overall "significant decrease" in the strength of emotional experience.

This seems like pretty bogus info to me but you never know. It always makes me leary when there's press around terms like 'significant decrease'.

Of course, there's also this; 

A new study by the US Association for Psychological Science has found that the anti-wrinkle treatment, which works to smooth fine lines by paralyzing muscles in the face, actually has an effect on the brain as well, reports London’s Telegraph.

40 volunteers in the study, done by researchers from the University of Wisconsin, were evaluated both before and after having Botox injections. Their response time was recorded as they read a series of statements out loud, with content ranging from "angry" to "sad" to "happy."

The study found that the subjects took longer to read the more "negative" passages after the injections than before. Researcher David Havas told the Telegraph this delay was small but critical because it implies that the brain was processing the negative emotion more slowly after the drug's injection.

"Normally, the brain would be sending signals to the periphery to frown, and the extent of the frown would be sent back to the brain," explained research leader Professor Arthur Glenberg. "But here, that loop is disrupted, and the intensity of the emotion and of our ability to understand it when embodied in language is disrupted."

In other words, when your face stops frowning, your brain gets the message that you've decided there's less to frown about.

"There is a long-standing idea in psychology called the facial feedback hypothesis," Havas told the Telegraph, who believes the new study shows that, "When you're not frowning, the world seems less angry and less sad."

So does this mean that those getting Botox not only have smoother faces than their Botox-free friends but are happier too?

Not necessarily. A study published earlier this year in the Journal of Cosmetic Dermatology found that when injections of Botox are used to paralyze some facial muscles, other nearby muscles have to work overtime to compensate, creating even more lines in the face.