In the United Kingdom, antidepressant prescriptions have more than doubled over the past decade, with roughly 8–9 million adults now receiving selective serotonin reuptake inhibitors (SSRIs) or serotonin–norepinephrine reuptake inhibitors (SNRIs). Most of these prescriptions are written for long-term maintenance therapy, yet the evidence base supporting extended use is surprisingly thin. Relapse prevention trials, which could clarify optimal duration and tapering strategies, remain underfunded relative to acute-phase research. This mismatch between prescribing practice and the available evidence carries real consequences for patients and clinicians alike.

The Prescription Rise That Outpaces the Evidence

Between 2015 and 2025, the number of antidepressant items dispensed annually in England rose from around 60 million to over 120 million, according to NHS Business Services Authority data. The increase reflects both a higher prevalence of diagnosed depression and a trend toward longer treatment courses. Many patients now stay on medication for years, sometimes indefinitely, after a single depressive episode.

Clinical guidelines from the National Institute for Health and Care Excellence (NICE) recommend continuing antidepressants for at least six months after remission to prevent relapse. For those with recurrent depression, maintenance therapy of two years or more is advised. However, these recommendations rely heavily on indirect evidence — meta-analyses of short-term trials and observational studies — rather than large, placebo-controlled relapse prevention trials that follow patients for extended periods.

The mismatch is striking. While acute-phase efficacy is supported by hundreds of randomized controlled trials, the number of studies examining long-term relapse prevention is modest. A 2021 Cochrane review identified only 34 trials that compared continued antidepressant treatment with placebo for relapse prevention, and most lasted no longer than 12 months. Fewer than a handful extended beyond two years.

Some researchers argue that the evidence gap stems partly from the difficulty of conducting such trials. Discontinuation symptoms — dizziness, nausea, headache, and emotional lability — can mimic depressive relapse, making it hard to distinguish between withdrawal and a true recurrence. Blinded, placebo-controlled designs are expensive and require large sample sizes to detect modest effect sizes over long follow-up periods.

Why Relapse Prevention Data Matter for Maintenance

Relapse prevention trials address a fundamentally different question than acute-phase studies: Does continued treatment reduce the risk of a new depressive episode in someone who has already recovered? Without robust data, clinicians cannot be certain whether the benefits of prolonged therapy outweigh the risks, which include side effects such as weight gain, sexual dysfunction, and the potential for withdrawal syndromes upon discontinuation.

A landmark trial by Kupfer and colleagues in the early 1990s showed that imipramine reduced relapse risk in recurrent depression over three years, but that study used a tricyclic antidepressant rarely prescribed today. More recent trials with SSRIs, such as sertraline and fluoxetine, have reported similar benefits, but effect sizes vary widely and dropout rates are high. A 2023 meta-analysis of 28 relapse prevention trials found that antidepressants reduced relapse risk by about 40% compared with placebo over 6–12 months, but the absolute risk difference narrowed after the first year.

Critics point out that many trials exclude patients with complex comorbidities, such as anxiety disorders or substance use, who represent a large proportion of real-world primary care populations. General practitioners (GPs) are left to extrapolate from study populations that may not reflect their daily caseload. The result is a wide variation in prescribing practices, with some GPs continuing medication indefinitely and others attempting tapering without clear protocols.

Patient perspectives add another layer of complexity. Surveys conducted by the charity Mind indicate that many individuals feel uninformed about the long-term effects of antidepressants and the process of discontinuation. Shared decision-making is hampered by the lack of reliable data on how long treatment should last and what tapering schedule works best.

The Funding Gap in Depression Maintenance Research

Mental health research in the UK receives a fraction of overall health research funding. According to the UK Research and Innovation (UKRI) mental health research budget, which is roughly £200 million per year, relapse prevention trials account for a small proportion. An analysis of publicly funded depression trials in the UK from 2010 to 2022 found that only 6% focused on maintenance or discontinuation strategies.

Industry-funded trials overwhelmingly prioritize acute-phase efficacy and short-term safety, as these are required for regulatory approval and marketing. Once a drug is licensed, pharmaceutical companies have little incentive to invest in long-term relapse prevention studies, which are costly and may reveal modest benefits or high dropout rates. Academic funders, meanwhile, often favour mechanistic biomarker research over pragmatic clinical trials.

This imbalance has been noted by the All-Party Parliamentary Group on Prescribed Drug Dependence, which in 2023 called for more research into antidepressant withdrawal and long-term outcomes. The group highlighted that the lack of evidence contributes to prolonged prescribing and inadequate support for patients wishing to stop medication.

Some researchers advocate for repurposing existing trial networks. The Clinical Practice Research Datalink, which contains anonymized primary care records for millions of UK patients, could be used to conduct registry-based randomized trials at a fraction of the cost of traditional studies. Pilot projects using this approach have shown feasibility in other areas, such as hypertension and diabetes, but have not yet been scaled for mental health.

What Happens When the Evidence Base Is Thin

Without clear guidance, GPs often continue antidepressant prescriptions indefinitely. A study published in the British Journal of General Practice in 2022 found that among patients who had been on antidepressants for at least two years, only about one in five had a documented discussion about discontinuation in the previous year. Many patients report being told they may need medication for life, a message that can create dependency and anxiety about stopping.

Withdrawal syndromes are a common but underrecognized consequence. The Royal College of Psychiatrists updated its guidance in 2024 to acknowledge that a significant proportion of patients experience discontinuation symptoms, some of which can be severe and prolonged. Yet training for GPs on tapering protocols remains limited, and specialist services for complex withdrawal are scarce outside major cities.

Psychological alternatives, such as cognitive behavioural therapy (CBT) and mindfulness-based cognitive therapy, have shown promise in preventing relapse, but access is uneven. The NHS Improving Access to Psychological Therapies (IAPT) programme has expanded in recent years, but waiting times can be months, and the therapy offered may not be tailored to maintenance needs. A 2023 trial in Scotland found that combining antidepressant tapering with CBT reduced the risk of relapse compared with tapering alone, but the study was small and has not been replicated.

The consequences extend beyond individual patients. The NHS spends roughly £200 million annually on antidepressants, and the opportunity cost of long-term prescribing without adequate evidence is substantial. Redirecting some of that expenditure toward research could yield better outcomes for patients and the healthcare system alike.

Trade-offs and Counter-Arguments: Why the Evidence Gap Persists

Some commentators argue that the evidence gap is not as severe as it appears. They point to the large number of acute-phase trials and the consistency of their results, suggesting that the benefits of antidepressants in preventing relapse are well established by indirect evidence. For example, if a drug is effective in acute treatment, it is reasonable to assume it continues to work in maintenance, especially since most relapses occur within the first year after recovery. Moreover, the 2023 meta-analysis showing a 40% relative risk reduction is often cited as sufficient to justify long-term use.

However, critics counter that indirect evidence is not a substitute for direct comparisons. The acute-phase trials typically exclude patients who have already responded to treatment, and the mechanisms of relapse may differ from those of initial episodes. Furthermore, the high dropout rates in long-term studies — often exceeding 30% — raise questions about tolerability and the generalizability of findings. A patient who discontinues due to side effects is not captured in the efficacy analysis, but their experience is relevant to real-world prescribing.

Another counter-argument concerns the role of natural recovery. Some patients who remain on antidepressants for years might have recovered without medication, and the drug may be providing little additional benefit. Without a placebo control over extended periods, it is impossible to know. This is particularly relevant for patients with mild to moderate depression, where the acute-phase benefit is already modest.

From a funding perspective, some researchers argue that investing in relapse prevention trials may not be cost-effective compared to other priorities. The cost of a single large-scale trial can exceed £10 million, and the results may only apply to specific drugs or populations. Instead, they advocate for better use of observational data from electronic health records, which can provide real-world evidence on long-term outcomes at lower cost. However, observational studies are prone to confounding by indication — patients who stay on medication may differ systematically from those who stop — making causal inference difficult.

International Comparisons: How Other Countries Handle the Gap

The UK is not alone in facing this evidence gap. In the United States, the National Institute of Mental Health has funded several long-term studies, but most have focused on treatment-resistant depression or augmentation strategies rather than simple relapse prevention. A notable exception is the STAR*D trial, which followed patients for up to 12 months after initial treatment, but it did not include a placebo group for maintenance. In Europe, the Netherlands has invested in pragmatic trials using primary care databases, with a focus on tapering and discontinuation. The Dutch DISCONTINUE trial, for example, compared two tapering schedules and found that a slower taper reduced withdrawal symptoms, but the sample was small and the follow-up limited to three months.

Australia has taken a different approach, emphasizing shared decision-making tools and patient education. The Beyond Blue initiative provides online resources for patients considering discontinuation, but these are not based on controlled trials. In Canada, the Canadian Network for Mood and Anxiety Treatments (CANMAT) guidelines recommend maintenance therapy for at least two years after a single episode, but acknowledge the low quality of evidence. The variation across countries underscores the need for international collaboration and standardized protocols.

A Path Forward: Pragmatic Trials and Real-World Data

Addressing the evidence gap does not necessarily require expensive, large-scale trials. Pragmatic trials embedded in routine clinical practice can generate useful data at lower cost. For example, the UK's National Institute for Health Research has funded a feasibility study in Scotland that uses GP practice randomization to compare different tapering schedules. Early results suggest that patient retention is acceptable and that routine outcome measures can be collected electronically.

Registry-based randomization, which uses existing healthcare databases to assign patients to different treatment strategies, could be scaled up for depression maintenance research. The Danish iCARE programme has demonstrated the feasibility of this approach for smoking cessation and alcohol reduction; a similar model could be adapted for antidepressant discontinuation. Linking prescription data with hospital records and patient-reported outcomes would allow researchers to track relapse rates, adverse events, and quality of life over years.

Standardization of outcome measures is another priority. Researchers and clinicians disagree on how to define relapse, with some using diagnostic interviews and others relying on symptom scales. Harmonizing definitions would make it easier to compare results across studies and meta-analyses. Patient-reported outcomes, such as the Patient Health Questionnaire (PHQ-9), are widely used but may not capture the full picture of recovery and functioning.

Finally, funding bodies need to prioritize maintenance research. The UKRI and the National Institute for Health and Care Research could set aside a dedicated budget for pragmatic trials in long-term antidepressant therapy. Charitable funders, such as the Wellcome Trust and the Mental Health Foundation, have begun to call for more investment in this area, but concrete commitments remain modest. Without a coordinated effort, the evidence gap is likely to persist, and millions of patients will continue to take medications whose long-term effects are not fully understood.

For readers interested in how other countries handle similar evidence gaps in mental health care, our article on India's public psychiatric hospitals highlights the challenges of resource allocation in treating severe cases. Meanwhile, the debate over screening and false positives in other areas of medicine, such as Dutch mammography, underscores the importance of robust evidence before widespread implementation.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before making changes to your medication regimen.