Can Mounjaro Cause Low Mood or Depression?

What the SURMOUNT programme actually recorded on mood

The SURMOUNT-1 trial (which followed over 2,500 adults with obesity over 72 weeks) tracked a broad range of adverse events, with the dominant signals being gastrointestinal: nausea, diarrhoea, constipation, and related symptoms. Psychiatric adverse events, including low mood and depressive symptoms, were monitored throughout but were not among the findings that distinguished tirzepatide from placebo. The trial data, published in the New England Journal of Medicine, showed no statistically meaningful difference in mood-related events between the groups. That does not mean no individual in the trial experienced low mood — it means the rate was not higher than in people who took no medicine at all. The distinction matters.

Regulatory scrutiny since then has been active. The European Medicines Agency reviewed GLP-1 receptor agonists, including semaglutide and liraglutide, for a potential association with suicidal ideation and self-harm following early spontaneous reports. Their 2024 conclusion found no established causal link. Tirzepatide's dual-agonist mechanism means it cannot be assumed to behave identically to GLP-1 mono-agonists, and ongoing pharmacovigilance continues across the class. The MHRA's Drug Safety Update index is the right place to track any new communications on this topic as they emerge.

The current licensed position: low mood is not a recognised adverse effect of Mounjaro in the UK SmPC. Prescribers are nonetheless expected to consider a patient's mental-health history before initiating treatment.

Why mood can shift during weight-loss treatment, even without a direct drug effect

This is a question our prescribers hear most weeks, and it is worth separating carefully. Weight loss, particularly when it happens relatively quickly, brings physical and psychological changes that have nothing to do with tirzepatide's pharmacology.

Calorie restriction reduces intake of nutrients including B vitamins, iron, and tryptophan, a precursor to serotonin. If food intake falls sharply without attention to nutritional quality, mood can dip for reasons that are dietary rather than pharmacological. Fatigue is also common in the early weeks, partly because the body is adjusting to lower energy availability, and fatigue and low mood are closely entangled. Add to this the social dimension: meals are often social occasions, and appetite suppression can subtly alter routines in ways that feel isolating before people notice why.

There is also a less-discussed counterpoint. Many people report improved mood and self-confidence as weight loss progresses, particularly once the initial gastrointestinal adjustment phase passes. The relationship between bodyweight and mental health is genuinely bidirectional, obesity itself is associated with higher rates of depression, and for some patients, effective treatment produces psychological benefit. The picture, in other words, is rarely linear. Reading more about the broader side-effect profile of Mounjaro can help put individual symptoms in context.

When to take emotional changes seriously and what to do

Mood fluctuations in the first few weeks of treatment (mild irritability, low energy, or feeling slightly flat) are reported by some people and are generally not a reason to stop. They often coincide with the phase when nausea is most noticeable and eating patterns have changed most sharply. If you are wondering whether Mounjaro can affect your mood and what the evidence actually says, our dedicated page works through that question in detail.

The threshold for contacting your prescriber promptly is lower than people sometimes assume. Seek help (not at your next scheduled review but sooner) if you notice persistent low mood lasting more than a week or two, a loss of interest in things you normally value, significant changes in sleep, or any thoughts of self-harm or suicide. Our page on Mounjaro and low mood covers what to watch for and how to tell whether what you are feeling needs clinical attention. Do not stop the medicine abruptly without speaking to a clinician first; withdrawal is not the risk it is with some other drug classes, but a supervised decision is always better than an unsupported one.

If you are experiencing thoughts of self-harm right now, the right route is your GP, 111, or the Mind helpline, not an online pharmacy consultation. Emotional safety takes priority over everything else.

For anyone already on treatment who wants to discuss how they are feeling, our prescribers are available for aftercare seven days a week. You can reach the team via our contact page, or read more about how the service works on the about us page. A fuller breakdown of the mood-related side effects associated with Mounjaro, including how commonly they are reported and what the clinical guidance says, is available on the Mounjaro overview page. For a closer look at how Mounjaro can interact with mood across different stages of treatment, including what patients and clinicians most commonly report, that page brings together the key information in one place. It is also worth knowing that gut symptoms and emotional wellbeing are more connected than they might seem, so if you have questions about whether Mounjaro can cause diarrhoea and how that fits into the wider side-effect picture, the dedicated page covers the evidence in detail.

If you have not yet started treatment and want to discuss your mental-health history as part of the clinical assessment, that conversation happens at consultation. The prescriber (a GPhC-registered Independent Prescriber who reads every response personally) takes that history into account before making any prescribing decision. You can start your free consultation here.