Is America's falling fertility rate caused by the overprescription of ... trends now

America's plummeting fertility rate may be linked to the over-prescription of antidepressants, experts have warned. 

Since becoming widespread in the 1980s, scripts for the mood-boosting drugs have skyrocketed, with a record nearly one in five adults taking them in 2020 compared to around one in 50 at the turn of the century.

During that time, America has also experienced a sharp decline in fertility rates, reaching a historic low in 2020.  The country's so-called baby bust has been attributed to a multitude of factors, from changing family values to women focusing on their careers and sedentary lifestyles.

But doctors say the rapid rise of antidepressants could also be tied to the phenomenon.  

Dr Helen Bernie, director of male sexual and reproductive medicine at Indiana University, told DailyMail.com that while side effects of antidepressants such as headaches and digestive issues are well known, there is another that is rarely talked about.

Due to the way that they act on the brain's neurotransmitters, the most popular type of antidepressant known as SSRIs lower sperm speed and shape, as well as reduce interest in sex, making people less likely to have kids.  

Dr Bernie said the drugs can 'have a significant impairment on men's sperm quality,' which directly impacts their ability to conceive. 

This includes the concentration, how fast sperm moves, and its shape. 

A 2022 meta-analysis in the journal Frontiers in Pharmacology found that SSRIs have 'a statistically significant impairment on semen quality, such as sperm concentration, sperm morphology, sperm motility,' the researchers wrote. However, semen volume was not impacted. 

This could contribute to the overall fertility rate in the US, which has been steadily falling for decades. 

In the US, women had an average of just 1.7 children, according to the United Nations' World Population Prospects, in 2020. In 1970, that rate was 2.3.

The global fertility rate- the average number of children born to each woman- was 2.3 in 2020, compared to 4.7 in 1970. This is a staggering 51 percent drop. 

The rising age of women in the US and falling birthrates have been attributed to women leaving it until later in life to have children to pursue careers, changes in familial values as well as advances in IVF and other fertility treatments.

Other lifestyle factors that can lower libido are also on the rise, including obesity, high blood pressure, poor diet, and sedentary lifestyles.  

But several doctors believe antidepressants could be closely tied to the phenomenon.

Serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed type of antidepressant, accounting for up to 70 percent of all antidepressant prescriptions. 

They work by increasing levels of serotonin in the brain, a neurotransmitter that carries signals between nerve cells throughout the body. 

Serotonin regulates several vital functions, including mood, sleep, digestion, memory, and learning. 

SSRIs block serotonin from getting reabsorbed into neurons, or brain nerve cells. This makes more serotonin available to the brain, which can alleviate mental health conditions like depression and anxiety. 

These medications have no bearing on sperm volume, but they can diminish quality. 

'[SSRIs impact] not only their sperm concentration and their counts for the number of sperm, but it also impacts the sperm motility, or how fast it swims,' Dr Bernie said. 

SSRIs can also inhibit sperm morphology, or the shape of the sperm needed to penetrate the egg, as well as DNA fragmentation index, the measurement of sperm DNA abnormalities. 'They do have a significant impact,' Dr Bernie said. 

A 2020 study in the International Journal of Urology, for example, detailed that men who took SSRIs had just 61 million sperm versus the 184 million from men who didn't take them.