While Botox injections are known for tightening saggy facial features, a new study suggests that women are more likely depressed because they lost their ability to smile.

Psychologist Michael Lewis from the Cardiff University in United Kingdom explained his findings on April 11 at the annual British Psychological Society conference, which found that the injections freeze the muscles of the face and halts signals from reaching the brain when someone feels happy enough to smile.  But because those signals are cut off, it may trigger symptoms of depression.

"The expressions that we make on our face affects the emotions we feel; we smile because we are happy but smiling also makes us happy," Lewis told Health Canal. "Treatment with drugs like Botox prevents the patient from being able to make a particular expression."

He examined 25 women with Botox injections or fillers for crows feet or frown lines. The women also completed a questionnaire that asked for their symptoms of depression two to four weeks after the treatment.  Those who were given crows feet procedures had depression scores more than 50 percent higher than those treated for frown lines.  

Lewis previously found that those who were treated with Botox experienced denervation of their frowning muscles and couldn't frown, so they were noticeably happier than those who received other types of facial treatment.

"This interrupts the feedback they would normally get from their face and they feel less sad," he added.

This current research concerns those who are receiving injections for crows' feet because their eye muscles are part of forming a real smile, so applying Botox to this area reduces the power of a smile.

According to The American Academy of Facial Plastic and Reconstructive Surgery, Botox and hyaluronic acid fillers were the top most facial injections treated for forehead, cheeks and lips.  Suprisingly, the number of men who were treated with Botox jumped 27 percent from 2011.

The reasons why Botox is popular is because it's one of the most affordable procedures, costing $375 on average per treatment and cosmetic businesses have been booming--adding more than $1 billion a year in revenue.  Since 2000, the number of reported Botox procedures have been up 621 percent.