SSRI antidepressants save lives. They treat depression, reduce anxiety, and restore sleep. But they carry a devastating side effect for many: sexual dysfunctions that affect up to 70% of patients. And that's not all: add decreased desire, erectile dysfunction, and the inability to achieve orgasm. The problem is, there's no way to know who will be affected until it's too late. Until now.
A team of Danish researchers has developed an EEG test that measures serotonin levels in the brain. and predicts with 87% accuracy who will develop sexual problems during therapy. The test is called LDAEP And it works like a hearing test that also reveals brain chemistry. It only takes 30 minutes to know if that drug will harm your sex life.
The game-changing discovery
The team led by Kristian jensen ofUniversity of Copenhagen studied 90 people diagnosed with depression. The researchers measured serotonin activity in the brain using the test LDAEP (Loudness Dependence of Auditory Evoked Potentials), a test that analyzes how the brain reacts to sounds. The lower the response, the higher the serotonin. The patients then began an 8-week course of SSRI antidepressants, carefully monitoring any sexual side effects. The results, presented at the 2025 National Astronomy Meeting of the Royal Astronomical Society in Durham, have shown something specific: Those who had high serotonin levels before treatment were much more likely to lose the ability to reach orgasm.
By combining the LDAEP test with information about sexual problems related to depression, the researchers predicted the ability to achieve orgasm with 87% accuracyMore data is needed for erectile dysfunction, but the direction is clear.
The problem with antidepressants that no one tells you beforehand
Sexual dysfunctions induced by SSRIs are not a marginal detail. They affect between 30% and 70% of patients, According to recent studies published in psychiatric journalsDifficulty achieving orgasm, decreased libido, erectile dysfunction in men, difficulty with lubrication in women. Symptoms that persist throughout the duration of therapy. In some cases, as documented byEuropean Medicines AgencyThese problems can continue even after stopping the drug, resulting in post-SSRI sexual dysfunction (PSSD). It's a kind of side effect that refuses to go away, even after the drug is stopped.
The mechanism is simple to understand. SSRI drugs They work by increasing serotonin levels in the brain, which improves mood. However, serotonin has an inhibitory effect on sexual function.: More serotonin means less dopamine and norepinephrine, the neurotransmitters that regulate desire and arousal.It's as if the drug that brings back your smile takes away your ability to enjoy another kind of pleasure. And there's no way to predict it. Until you start therapy.
How the LDAEP test works
I'll keep it simple, but you can delve deeper if you want. They put headphones on you, play sounds at increasing volumes, and measure how your brain reacts via an electroencephalogram (EEG). The brain's response to sounds of varying intensity reveals how active serotonin is.
It's a bit like measuring the activity of an invisible chemical system using only sound waves and brain waves. It lasts about 30 minutes, is non-invasive, and does not require blood sampling.. As Jensen explained:
"These signals allow us to measure serotonin activity before the patient takes the first pill. If the levels are high, we can choose another antidepressant."
The test is currently not available in daily clinical practice, but it could become so if further studies confirm the results. The researchers They are now conducting a study on 600 patients to definitively validate the method and understand how serotonin levels interact with sex hormones during therapy. If it works, it will be a breakthrough.
An underestimated public health problem
The use of antidepressants has exploded in the last twenty years. In Italy, according to data from theItalian Drug Agency, SSRI use doubled from 2000 to 2020We're talking about millions of people. If even just 30% develop serious sexual dysfunction, we are looking at hundreds of thousands of patients who stop therapy for this reason, with consequences on their mental health.
As he pointed out Eric Ruhe, professor of psychiatry at the Radboud University in the Netherlands:
"This test could especially help patients who hesitate to start treatment precisely because they fear the sexual side effects. Being able to say with reasonable certainty that they won't have any problems would change everything.".
The vision is for precision medicine applied to psychiatry: no more blindly prescribed drugs, but personalized therapies based on individual brain chemistry.
Researchers are also exploring alternatives. Some antidepressants, such as bupropion and mirtazapine, have a much lower sexual side effect profile. But without a predictive test, the choice remains empirical. The LDAEP test could change this, allowing doctors to select the right drug the first time.
Antidepressants and their effects on libido: the test exists, but validation is needed.
The current study involved 90 patients, 73% of whom were women and with an average age of 27. It's a limited sample, and the researchers are aware of this. Therefore, as mentioned, they are working on a large-scale validation with 600 participants, including more men and a broader age range. If the results are confirmed, the LDAEP test could become an integral part of the initial evaluation for anyone who needs to start therapy with SSRIs.
The technology exists. The test works. Serotonin can be measured. It remains to be seen whether the healthcare system will be ready to adopt it. But the promise is clear: fewer patients discontinuing treatment, fewer ruined sex lives, more people able to seek treatment without having to choose between their mental health and their intimate lives.
It's not little.
