Montelukast, sold under the brand name Singulair and widely prescribed for asthma and allergic rhinitis, carries a boxed warning from the U.S. Food and Drug Administration for serious mental health side effects. Reported problems range from vivid nightmares and agitation to depression, anxiety, and suicidal thoughts. The warning, added in March 2020, was the culmination of over a decade of regulatory reviews prompted by a steady stream of patient and caregiver reports. What makes this topic unusually complicated is a genuine tension in the evidence: individual case reports are alarming, while large population studies show only modest increases in risk, and some show no increase at all.
How the FDA Warning Came About
The FDA first flagged postmarketing reports of neuropsychiatric problems with montelukast back in 2007. Over the following years, the agency conducted multiple reviews of clinical trial safety data, published literature, and focused analyses of adverse event reports. Each round led to updated label language, but prescribers and patients often remained unaware of the risk. By 2019, the agency held a public advisory committee meeting to discuss whether stronger action was needed. The panel recommended a boxed warning, the most prominent safety alert the FDA can require on a drug label.
In March 2020, the FDA required the boxed warning and also restricted the allergic rhinitis indication, reserving montelukast for patients who don’t respond to or can’t tolerate other treatments. The asthma indication stayed unchanged, reflecting a judgment that for asthma, the breathing benefits still justify the risk for most patients.1The Journal of Allergy and Clinical Immunology: In Practice. A Boxed Warning for Montelukast: The FDA Perspective That distinction matters: if you take montelukast for hay fever alone, the FDA’s position is that safer options should be tried first. If you take it for asthma, the benefit-risk balance is viewed more favorably, though awareness of mental health risks is still expected.
What the Mental Health Side Effects Look Like
The neuropsychiatric symptoms linked to montelukast span a wide range. Nightmares are among the most commonly reported, particularly in children. A large analysis of the World Health Organization’s global adverse drug reaction database found that about 32% of all montelukast reports flagged a psychiatric problem, compared to roughly 8% for drugs overall.2PubMed Central. Montelukast and Nightmares: Further Characterisation Using Data from VigiBase That’s a striking difference, though it reflects what gets reported to regulators rather than what happens to all users. People who have a bad reaction are far more likely to file a report than people who feel fine.
Beyond nightmares, reported effects include aggression, irritability, anxiety, depression, insomnia, and in rare cases, suicidal ideation or behavior. A BMJ review noted these effects have appeared in patients of all ages, including people with no prior psychiatric history, and occasionally persist or emerge even after stopping the drug.3BMJ. Neuropsychiatric reactions with the use of montelukast The variety of symptoms can make them hard to recognize as drug-related. A child who starts having nightmares or becoming uncharacteristically aggressive might not immediately trigger a connection to the little pill they chew each evening.
The Evidence Is More Mixed Than Headlines Suggest
This is where the story gets genuinely complicated. Adverse event databases, where patients and doctors voluntarily report suspected drug reactions, show an unmistakable signal for montelukast and psychiatric problems. But when researchers look at large insurance-claims databases or conduct controlled observational studies, the picture softens considerably.
A 2022 study that analyzed claims data from millions of patients found that montelukast users had a modestly higher rate of neuropsychiatric diagnoses compared to non-users. The increased odds were about 11% higher in patients with asthma and about 7% higher in patients with allergic rhinitis. The strongest associations were for anxiety and insomnia rather than depression or suicidal behavior.4JAMA Network Open. Analysis of Neuropsychiatric Diagnoses After Montelukast Initiation An 11% increase in relative risk sounds worrying in isolation, but it translates to a small absolute number of additional cases. If your baseline chance of developing anxiety in a given period is, say, 5%, an 11% relative increase bumps that to about 5.5%.
Other studies have found even less cause for alarm. A large study comparing montelukast users to people taking inhaled corticosteroids found no increased risk of inpatient depression or self-harm.5PubMed. Risk of Psychiatric Adverse Events Among Montelukast Users A study of children and young adults prescribed leukotriene-modifying agents found no increase in suicide attempts; the direction of the effect actually trended in the opposite direction.6PubMed. Risk of suicide attempt in asthmatic children and young adults prescribed leukotriene-modifying agents: a nested case-control study And an earlier investigation that specifically searched for completed suicides among montelukast users found none in its study population.7PubMed. Rate of suicide in patients taking montelukast
A 2025 meta-analysis pulled these threads together and concluded that montelukast is associated with a modestly increased risk of anxiety, but found no consistent evidence for increased depression or suicidal behaviors.8PubMed Central. Montelukast: risk of mental disorders vs. efficacy–a meta-analysis Similarly, a Korean national health insurance database study found no increased risk of a composite neuropsychiatric outcome in asthma patients prescribed montelukast or the related drug pranlukast.9PubMed. The Risk of Neuropsychiatric Adverse Events With Use of Leukotriene Receptor Antagonists in Patients With Asthma: Analysis of Korea’s National Health Insurance Sharing Service Database
So why the disconnect? One factor is that voluntary adverse event reports are biased toward dramatic cases. Another is that asthma and allergies themselves are linked to higher rates of anxiety and sleep disruption, making it hard to untangle the drug from the disease. Observational studies try to control for this, but the confounding is never perfectly eliminated. The honest summary is that montelukast probably does increase the risk of certain psychiatric symptoms in a subset of users, but the absolute risk for any individual is small, and the most severe outcomes (suicidal behavior, psychosis) appear to be rare.
How Symptoms Differ by Age
The psychiatric profile of montelukast reactions isn’t the same across the age spectrum. An analysis of the WHO’s VigiBase database organized by age group found distinct patterns. In infants under two, sleep disturbances dominated the reports. In children aged two to eleven, depression, anxiety, and aggression were the leading concerns. In adolescents, suicidal behavior and depression stood out.10PubMed. Psychiatric Disorders and Montelukast in Children: A Disproportionality Analysis of the VigiBase
A separate study looking at adverse drug reactions across all ages confirmed that aggression was especially over-reported in children, while depression was the most frequently reported psychiatric event in the overall population.11PubMed Central. Adverse drug reactions of montelukast in children and adults This age-related pattern makes clinical sense. Young children are more likely to manifest psychiatric distress through behavior (tantrums, aggression, sleep problems) rather than through the mood and thought symptoms an adult might describe. It also means that parents need to watch for different signals than adults would watch for in themselves.
One striking finding from the VigiBase analysis was that completed suicides were reported more frequently in children aged two to eleven than in adolescents or the general population.12PubMed. Psychiatric Disorders and Montelukast in Children: A Disproportionality Analysis of the VigiBase That statistic is difficult to interpret. It may reflect reporting patterns, or it may reflect a genuinely concerning signal in a vulnerable group. Either way, it was part of the body of evidence that led to the FDA’s decision to add the boxed warning.
Compared to Inhaled Corticosteroids
Because montelukast and inhaled corticosteroids are both first-line options for asthma, comparing their psychiatric safety profiles is the most practical question for many patients. A large comparative study found that leukotriene receptor antagonists like montelukast carried a slightly higher rate of neuropsychiatric adverse events than inhaled corticosteroids: about 25 events per 1,000 person-years versus about 23.5 per 1,000 person-years. Anxiety and behavioral/emotional disorders were modestly more common in the montelukast group, with a notably higher rate of psychotic disorders (though psychotic disorders were rare in both groups). There was no significant difference for mood disorders, sleep-related disorders, or personality disorders.13PubMed. Comparative Risk of Neuropsychiatric Adverse Events Associated With Leukotriene-Receptor Antagonists Versus Inhaled Corticosteroids
The absolute difference between the two treatments is small. For every 1,000 patients treated for a year, the data suggest roughly one to two extra neuropsychiatric events with montelukast compared to inhaled corticosteroids. That’s a real difference, but it’s not the kind of chasm you might expect from the intensity of the public discussion. For a patient who struggles with inhaler technique, can’t tolerate the local side effects of corticosteroids, or simply does better on a daily pill, the psychiatric risk of montelukast may be acceptable after a frank conversation about what to watch for.
Why Montelukast Might Affect the Brain
The biological question of how a drug designed to block inflammation in the airways could alter mood and behavior remains only partly answered. Montelukast blocks a receptor called CysLT1R, which responds to inflammatory molecules called cysteinyl leukotrienes. These receptors aren’t confined to the lungs; they’re also found in the brain, including the hippocampus, a region involved in mood regulation and memory.
Animal research has shown that blocking or knocking down CysLT1R in the hippocampus can actually reduce depressive-like behavior in mice and suppress brain inflammation.14PubMed Central. Hippocampal CysLT1R knockdown or blockade represses LPS-induced depressive behaviors and neuroinflammatory response in mice That’s a confusing finding if you expected the drug to make things worse. Other animal work has found that montelukast can improve memory in aging rats by reducing brain inflammation and promoting the growth of new brain cells in the hippocampus.15PubMed. Pharmaceutical Rejuvenation of Age-Associated Decline in Spatial Memory
The paradox is real: in animal models, blocking the same receptor montelukast targets tends to look neuroprotective. A small case series in humans even explored high-dose montelukast as a treatment for memory impairment and dementia, with memory-impaired patients reporting subjective improvement.16PubMed Central. Case Series Using Montelukast in Patients with Memory Loss and Dementia None of this proves montelukast helps the brain. But it does suggest that the relationship between this drug and the central nervous system isn’t simply “drug causes psychiatric harm.” There may be individual differences in how the leukotriene pathway interacts with other brain signaling systems, making the drug beneficial in some biological contexts and harmful in others. This remains an area of active research, and no one has a definitive molecular explanation for why a minority of users develop severe psychiatric symptoms.
How Prescribing Has Changed
The boxed warning had a measurable effect on how often montelukast gets prescribed. An interrupted time-series analysis of commercially insured patients with asthma found significant reductions in montelukast use after the warning, even though the asthma indication itself was not restricted.17PubMed Central. Changes in the Use of Montelukast for Asthma After a US Food and Drug Administration Boxed Warning Doctors shifted toward alternatives, and some patients already taking the drug were taken off it.
A single-center study looking at deprescribing patterns found that only about 4% of montelukast patients at that site went through a deprescribing event during the study period. Of those who did stop, the majority were removed during routine medication reconciliation rather than because of an explicit conversation about the boxed warning. Only a handful were discontinued specifically because of shared decision-making about the warning, an adverse event, or the development of suicidal ideation.18Exploratory Research in Clinical and Social Pharmacy. Montelukast deprescribing in outpatient specialty clinics: A single center cross-sectional study
The gap between the seriousness of the warning and the casualness of how it filters into practice is concerning. A survey of medical residents who had prescribed montelukast found that half were unaware of the boxed warning, and only about 30% felt comfortable counseling patients about neuropsychiatric risks.19Annals of Allergy, Asthma & Immunology. MINDFUL PRESCRIBING: ENHANCING RESIDENT AWARENESS OF MONTELUKAST ‘S NEUROPSYCHIATRIC RISKS That finding aligns with a common frustration among patients and parents who report learning about the warning only after their child developed symptoms, not before the prescription was written.
What to Watch For and When to Act
If you or your child is taking montelukast, the symptoms worth paying attention to depend partly on age. For young children, watch for unusual sleep disturbances (nightmares, night terrors, insomnia), new or escalating aggression, increased tantrums, or withdrawn behavior. For older children and teens, mood changes, new anxiety, irritability, and any mention of not wanting to be alive deserve immediate attention. For adults, the same list applies, with insomnia and anxiety being among the more commonly reported problems in the controlled data.
Most case reports describe symptoms emerging within days to weeks of starting the drug, though some develop only after months of use. The BMJ review noted that psychiatric effects have occasionally been reported after discontinuation, though this appears to be rare.20BMJ. Neuropsychiatric reactions with the use of montelukast For the majority of people who do develop symptoms, stopping the drug is the appropriate first step, and many report improvement within days to a few weeks. But “many” is not “all,” and there are patient accounts of symptoms lingering for months. The medical literature on long-term outcomes after discontinuation is thin, which is itself a problem.
If you notice a change, don’t wait for it to get worse before bringing it up with a doctor. The fact that large studies show only modest average risk increases does not mean that a given individual can’t have a severe reaction. The population-level statistics describe averages, while adverse drug reactions affect individuals. A drug that raises the average risk by a small amount can still cause profound harm in the person who happens to be susceptible.
The Reporting Paradox and Stimulated Reporting
One complication worth understanding is that the boxed warning itself may have changed the data. After the FDA added the warning in March 2020, the rate of adverse event reports for montelukast and psychiatric symptoms increased. A study examining FDA adverse event reporting found that the boxed warning was associated with a surge in reports of mental health side effects.21PubMed Central. The Impact of Montelukast’s Black Box Warning on Pediatric Mental Health Adverse Event Reports This phenomenon, sometimes called stimulated reporting, is well known in pharmacovigilance. When a safety concern becomes public, people who might have previously attributed their symptoms to something else start connecting them to the drug and filing reports. It doesn’t mean the new reports are wrong, but it means the raw count of reports after a warning is not a reliable measure of whether the drug actually became more dangerous. The drug didn’t change; awareness changed.
This matters because it feeds a circular cycle. More reports lead to more media coverage, which leads to more reports, which makes the adverse event database look increasingly alarming even if the underlying rate of actual reactions hasn’t changed. It’s one reason the controlled observational studies, which compare outcomes in matched patient groups regardless of whether anyone filed a report, tend to show much smaller effects than the raw adverse event data would suggest.
Montelukast for Allergic Rhinitis Versus Asthma
The distinction the FDA drew between the two indications is worth understanding on a practical level. For allergic rhinitis, alternatives like second-generation antihistamines and nasal corticosteroid sprays are effective for most people and don’t carry the same neuropsychiatric signal. The meta-analysis noted that montelukast shows comparable effectiveness to these alternatives, not superior effectiveness.22PubMed Central. Montelukast: risk of mental disorders vs. efficacy–a meta-analysis If you can control your allergy symptoms with a nasal spray or an antihistamine, there’s little reason to accept even a small psychiatric risk from montelukast.
For asthma, the calculus is different. Uncontrolled asthma is dangerous. Some patients, particularly children who can’t use inhalers effectively or adults who don’t respond well to inhaled corticosteroids alone, genuinely benefit from adding montelukast to their regimen. In those cases, the drug fills a role that isn’t easily replaced. The FDA’s decision to leave the asthma indication alone reflects the reality that breathing is not optional, and the absolute psychiatric risk increase from montelukast is small enough that it doesn’t outweigh the benefit for most asthma patients who need it. That said, “most” still leaves room for individuals who react badly, which is why the boxed warning exists for both indications: not to ban the drug, but to make sure the decision is made with open eyes.
A nationwide Danish cohort study looked at whether montelukast users were more likely to need neuropsychiatric medication or have a psychiatric hospital contact within 90 days of starting the drug.23PubMed. Psychiatric Adverse Effects of Montelukast-A Nationwide Cohort Study Studies designed this way are useful because they capture clinically meaningful outcomes, not just symptom checklists. When what you’re measuring is whether someone actually ended up needing psychiatric treatment, it sets a higher bar than survey-based reporting and gives a more grounded picture of how often montelukast creates problems that reach clinical severity.