A new study indicates that stimulating the serotonin 4 receptor may be an important way to treat people with depression, including increasing the possibility of experiencing well-being and access to pleasure, including sexual desire.
Depression can strike hard, and many people with moderate to severe untreated depression have the core symptom of anhedonia: reduced ability to experience pleasure in what used to be the highlights of their lives, including spending time with friends or family and sexual desire.
Researchers in Denmark recently found that depression is closely related to the concentrations of serotonin 4 receptors in the brain and that treatment with common drugs such as selective serotonin reuptake inhibitors typically improves sexual desire as the depression eases.
Now the same research group found that the concentrations of serotonin 4 receptors in the brain are significantly associated with low sexual desire among women.
“This is a very positive discovery, since one might fear that antidepressant treatment would reduce sexual desire. Instead, we showed that properly treating people with depression enhances sexual desire as well. In addition, we found a potential new target for anhedonia treatment and decreased desire: stimulating the serotonin 4 receptor, which also seems a promising target for other depressive symptoms,” explains a researcher involved in the studies, Vibe Frøkjær, Clinical Research Associate Professor, Department of Clinical Medicine, University of Copenhagen.
Investigated sexual desire among 85 people with depression
The study is an offshoot of the major NeuroPharm Depression study, in which the researchers monitor people with depression treated with antidepressants to determine how they fare in connection with the treatment.
In the substudy, the researchers aimed to determine whether the concentrations of serotonin 4 receptors in the brain of people with untreated depression are associated with anhedonia, represented by sexual desire.
The study included 85 people with moderate to severe depression who were brain scanned with positron emission tomography (PET) before starting treatment to measure the concentrations of serotonin 4 receptors in the brain.
The participants also self-reported information about sexual function by completing questionnaires before starting treatment and after 4, 8 and 12 weeks.
Of the 85 participants, 71% were women, which also roughly corresponds to the population distribution between men and women with depressive episodes.
“Our previous study showed that people with depression have lower concentrations of serotonin 4 receptors in the brain, but how this specifically relates to anhedonia, an important core symptom of depression, has been unknown,” says Vibe Frøkjær.
She elaborates that 85 people sounds like a small sample but is actually relatively large, since studies imaging the brain chemistry of people with depression often do not include more than 20–30 people.
Sexual desire improves with treatment
The results for the total group show no difference in the concentrations of serotonin 4 receptors in the brain between people with normal and dysfunctional sexual desire.
Nevertheless, when the researchers looked at women and men separately, they found that sexual desire before treatment was correlated with the concentrations of serotonin 4 receptors among women.
The lower the concentrations of serotonin 4 receptors in the depressed state, the lower the sexual desire.
According to Vibe Frøkjær, this naturally begs the question of whether antidepressant treatment, which stimulates serotonin 4 receptors in the brain, can also increase sexual desire among women with depression.
Need more personalised treatment
Vibe Frøkjær says that people with depression infrequently self-report the lack of sexual desire, which may result from this being far down the attention list for the difficulties people with depression face daily but also that patients and doctors may not be at ease in talking about sexual desire.
But also many people are concerned that side-effects of antidepressant treatment may affect sexual desire and thereby potentially affect their intimate relationships.
“The positive aspect is that we found that antidepressant treatment does not reduce sexual desire among most people – rather, typically it increases sexual desire by relieving anhedonia,” explains Vibe Frøkjær, who adds that the study also advances researchers’ knowledge on the biology behind anhedonia and offers strategies for how treatment could be more personalised.
“This encourages us to fine-tune the treatment of people with depression, who probably need tailored treatment in relation to their sex but also their age. One can easily imagine that reduced sexual desire affects one sex more strongly than the other and perhaps also younger people more strongly than older people,” concludes Vibe Frøkjær.