Could a Constipation Drug Help Clear the Fog After Depression?
- Joyce Knieff, ND, LAc
- Aug 10
- 4 min read
If you've come through a depressive episode and still feel like you're thinking through wet cotton, you're not imagining it, and you're not alone. Mood can lift while memory and focus stay stuck in the mud, and for a long time medicine hasn't had much to offer for that part specifically.
A new study out of the University of Birmingham and the University of Oxford tested a genuinely unexpected candidate: prucalopride, a drug approved to treat chronic constipation.
What the research found
Researchers recruited 50 adults, ages 18 to 40, each with a history of at least two depressive episodes. All of them had recovered and had been off antidepressants for at least six months, so the researchers could look at cognition without current mood symptoms muddying the picture. Half received a 2 mg daily dose of prucalopride; the other half got a placebo. Everyone took the pill for 7 to 10 days, then completed a battery of cognitive tests: verbal memory, working memory, executive function, and how quickly and accurately people read emotional expressions.
The prucalopride group did better on several fronts. They recalled more words on a memory task, responded faster on a demanding working-memory test without losing accuracy, and identified facial expressions more accurately [1]. Side effects were minimal, and no one dropped out over gut complaints, unsurprising given the drug's job is to gently encourage bowel movements, not disrupt them.
This is a randomized, placebo-controlled trial, though a small one. Fifty people is enough to detect a real signal but not enough to settle the question. The sample also skewed toward young, highly educated women, so how well this generalizes to a broader population is still an open question.
The bigger picture
This isn't the first hint that this receptor matters for the brain. Prucalopride showed similar memory benefits in healthy volunteers back in 2019 [2], and a 2021 imaging study found it boosted hippocampal activity during memory tasks [3]. On the observational side, a 2024 analysis of US health records found people who started prucalopride had a lower one-year risk of a new depression diagnosis than people started on other constipation drugs [4]. That's correlational data, not proof of cause and effect, but it points in the same direction. Separately, brain-imaging research has found that people with active depression have measurably fewer of these serotonin receptors than people without depression, and that having fewer of them tracks with worse verbal memory [5]. Put together, several independent research groups keep landing on the same receptor when they study memory and mood, using different methods each time.
The naturopathic lens
The receptor in question, 5-HT4, isn't just in the brain. It's dense in the gut wall too, which is exactly why a drug developed for constipation ended up in a depression trial in the first place.
That overlap isn't a fluke. Most of the body's serotonin is made in the gut, not the brain, and the enteric nervous system talks to the central nervous system constantly through the vagus nerve. When I'm working with a patient on mood and cognitive symptoms, I'm never looking at the brain in isolation. Gut motility, the health of the gut lining, and the balance of the microbiome all feed into that same serotonin signaling system. It runs both directions: a sluggish gut and an inflamed gut lining can worsen brain fog, and chronic stress or low mood can slow the gut right back down.
That's why addressing motility and gut healing is so often part of how we approach mood and cognitive complaints in practice, alongside everything else going on for a patient, not instead of it.
How to apply this now
Prucalopride is a prescription medication, and this study doesn't change how or when it should be used. It isn't approved for depression-related brain fog, so this is a research finding, not a treatment recommendation. If you're dealing with lingering memory or focus problems after a depressive episode, a few things are worth raising with your own care team: whether ongoing brain fog has been assessed separately from mood, whether digestive symptoms like constipation or bloating are part of your picture, and how your fiber, hydration, and movement habits are supporting your gut day to day. None of that replaces treatment for depression itself, but it's a reasonable starting point while research on this drug class continues.
References
De Cates AN, Hamilton S, Guru A, et al. Pro-cognitive effects of 5-HT4 receptor agonism in individuals with remitted depression. Psychological Medicine. 2026;56:e178. doi: 10.1017/S0033291726104450
Murphy S, et al. A role for 5-HT4 receptors in human learning and memory. Psychological Medicine. 2019.
de Cates AD, et al. Déjà-vu? Neural and behavioural effects of the 5-HT4 receptor agonist, prucalopride, in a hippocampal-dependent memory task. Translational Psychiatry. 2021.
de Cates AD, et al. Association between a selective 5-HT4 receptor agonist and incidence of major depressive disorder: an emulated target trial. British Journal of Psychiatry. 2024.
Köhler-Forsberg K, et al. Serotonin 4 Receptor Brain Binding in Major Depressive Disorder and Association With Memory Dysfunction. JAMA Psychiatry. 2023.
Original article: "Constipation Drug Could Help Clear Depression Brain Fog." Technology Networks, June 17, 2026. https://www.technologynetworks.com/drug-discovery/news/constipation-drug-could-help-clear-depression-brain-fog-413728
Disclaimer
This article is for general educational purposes only and is not a substitute for individualized medical advice, diagnosis, or treatment. Always talk with your own healthcare provider about any symptoms, medications, or changes to your care.
If this resonates with what you're experiencing and you'd like to explore a naturopathic approach, book a consultation with our clinic.
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