Botox injections can hide wrinkles by temporarily paralyzing the muscles that make us smile and frown. But a study in this month’s issue of the journal Emotion concludes that the process can also hinder the feelings that make us want to smile or frown in the first place. Here's a quick guide to the link between Botox and emotions:

How does Botox work?
Botox (or Botulinum toxin) injections smooth wrinkles by selectively paralyzing facial muscles. It's highly toxic, but in the 1950s doctors discovered that in very small doses it merely decreased activity in muscles. In 1989 the FDA approved Botox to treat some types of muscle spasms, and the drug gradually caught on for cosmetic treatment. Botox injections are now the most popular nonsurgical cosmetic procedure performed in the U.S.

What do the injections have to do with emotions?
Everyone knows that when we're happy, we smile, and when we're sad, we frown. But the researchers believe facial expressions actually reinforce and strengthen our experience of the underlying emotions. "It's like a continuous feedback loop," says Joshua Davis, lead author of the study. "If you take away some aspect of facial expression and feedback to the brain, you weaken the emotional experience."

How did the researchers reach that conclusion?
The psychologists who did the study recruited 68 people interested in getting rid of facial wrinkles. Half the participants got Botox injections, and half got Restylane, which is used to fill folds and wrinkles in the face without disabling the underlying muscles. Before and after treatment, the researchers showed the participants three types of videos to intended to evoke emotions. After starting injections, the Botox group reported a significant decrease in their emotional response.

Do the emotions come back?
The researchers are pretty sure that the emotional effects of Botox, like the physical effects, are only temporary. But it will take more research to determine whether some patients are more likely than others to feel their feelings deaden when the Botox kicks in. And if you believe drug-maker Allergan, which produces Botox, the emotions never go away at all. In response to the study, Allergan issued a statement saying there was no conclusive medical evidence proving that Botox injections affect patients' feelings in any way.

Sources: Toronto Star, WebMD, TechJackal, PsychCentral