Scientists have pinpointed a way to identify people who are at most risk of suffering from sexual issues while taking antidepressants. 

People who are prescribed a class of the mood stabilising drugs called selective serotonin reuptake inhibitors (SSRIs) often experience a loss of libido, become unable to obtain or maintain an erection, and are unable to ejaculate. 

These - very common - side effects can have a negative effect on self-esteem (making depression worse) and in some cases, they can lead to people stopping taking the medication altogether. 

A team of researchers from the University of Copenhagen in Denmark wanted to see if there was a way to identify patients most at risk of SSRI-related sexual dysfunction before they began taking the medication. 

They recruited a group of 90 people aged between 18 and 56 who had been diagnosed with major depressive disorder, but were not currently medicated. 

Of this group, 66 were women and 24 were men.  

The subjects were given a simple brain scan called an electroencephalogram (EEG) to establish the levels of serotonin in their brains before they were prescribed escitalopram, branded as Cipralex in the UK, for eight weeks. 

The researchers also assessed their sexual function before and after starting the drug.

Serotonin, often called the 'happy hormone'  is a neurotransmitter which helps regulate mood, sleep, appetite, and digestion and influences feelings of well-being. 

Low levels of serotonin can cause problems with mood including depression and anxiety. 

The researchers noted in their report, published in the Journal of Psychiatric Research: 'Sexual side effects such as decreased desire, arousal, and ability to orgasm are well documented and occur in 40–70 per cent of patients with [depression] treated with SSRIs. 

'Sexual side effects are some of the most common SSRI side effects, impacting quality of life, self-esteem, and relationships and contributing to medication non-adherence.' 

After the end of the eight weeks, the researchers found that the people with higher levels of serotonin were more likely to develop sexual side-effects from the SSRI, particularly difficulty achieving orgasm. 

Around two-thirds of patients (65 per cent) noticed some kind of sexual problem that they linked to the medication, and four 4 in 10 people (39 per cent) said the sexual problems were serious enough to become distressing. 

When doctors assessed the patients, they noted that 47 per cent had sexual side-effects caused by the SSRI medication, and 17 per cent (9 women and 4 men) reported suffering severe and distressing sexual side-effects. 

Across the group, sexual function dropped by nearly a quarter (23 per cent). 

The researchers hope that the study will influence how doctors treat people with depression, and will encourage them to measure and consider an individual's serotonin levels before prescribing SSRIs. 

However, they also noted some limitations, namely that women tend to experience sexual dysfunction before taking antidepressants (with men it is the opposite), and that the cohort was skewed more towards female participants. 

There has been an increase in people claiming to suffer with post-SSRI sexual dysfunction (PSSD), a very rare and somewhat controversial condition not yet recognised by the NHS.

Sufferers claim they that they have experienced long-term sexual issues after being prescribed SSRIs and are demanding that the condition to be recognised by healthcare professionals, and for more research into the long-term effects of SSRIs on sexual function.

A review by European Psychiatry say that there is 'growing evidence' that PSSD exists, in spite of the little research into the condition.

An early study into PSSD by Annals of General Psychiatry estimated that 1 in 216 patients have suffered with erectile dysfunction after stopping SSRIs.

The PSSD Network say that common issues include genital numbness, erectile dysfunction, vaginal dryness and a complete loss of libido.

The NHS does acknowledge that some people can get sexual side effects whilst taking SSRIs. 

Latest  statistics from the health body say 286,799 people aged five to 19 were prescribed antidepressants in 2024, compared to 242,629 in 2016.

Examples of SSRIs include citalopram, fluoxetine and sertraline, sometimes known by brand names Cipramil, Prozac and Lustral.