Montelukast, a widely prescribed medication for asthma and allergies, may cause significant psychiatric side effects that remain underdiagnosed and underreported, according to researchers. The researchers, from the University of California, Davis in the US, and Curtin University in Australia, said many psychiatrists are still unaware of the US Food and Drug Administration's (FDA) black-box warning on the drug's mental health risks.In 2020, the FDA had required a black-box warning for montelukast, citing the risk of serious behavior and mood-related changes, including suicidal thoughts or actions.Neuropsychiatric Side Effects More CommonWriting in Psychiatry Online, the researchers said that estimates of montelukast-related neuropsychiatric events range from 5.9% to 62%.Reported psychiatric side effects include:AggressionAnxietyDepressionSuicidal thoughts and behaviorSymptoms may appear soon after starting the medication, after prolonged use, or even following its withdrawal.Children at Greater RiskThe researchers noted that children appear to be disproportionately affected, partly because montelukast is available as a chewable tablet that is easier for young children to take than inhaled medications.Citing a 2016 study, they wrote that completed suicides were reported more frequently among children than among adolescents or the overall population.Behavioral changes in children may also be mistaken for normal developmental phases, delaying recognition of a possible drug-related cause.The researchers also highlighted testimony presented at a 2022 US National Center for Toxicological Research (NCTR) meeting, where a parent described severe behavioral changes in her three-year-old son after taking montelukast. Many parents at the meeting said they only discovered the possible link between the medication and psychiatric symptoms by chance, despite consulting multiple healthcare providers.Why the Link Is Often MissedResearchers said patients and clinicians frequently fail to connect psychiatric symptoms with montelukast because there is no obvious reason to suspect the medication.They also argued that inadequate communication from drug manufacturers and health regulators has contributed to low awareness, despite safety warnings issued in several countries.They cautioned that abruptly stopping montelukast may also worsen psychiatric symptoms, making clinical evaluation essential.What Psychiatrists Can DoThe researchers recommend that psychiatrists consider montelukast as a possible cause when psychiatric symptoms develop after the medication is started.If a link is suspected, psychiatrists should coordinate with the patient's primary care physician to discuss alternative treatments for asthma or allergies and monitor whether psychiatric symptoms improve.They also advise clinicians to:Consider montelukast use during emergency assessments for suicidal thoughts or suicide attempts.Monitor hospitalized patients who begin montelukast for newly emerging depression, anxiety, and suicidal ideation.What the FDA SaysThe FDA states that montelukast prescribing information already includes warnings about mental health side effects, including suicidal thoughts or actions. However, it notes that many healthcare professionals and patients remain unaware of these risks.The agency advises that:For allergic rhinitis (hay fever), montelukast should be reserved for patients who do not respond to or cannot tolerate other allergy medications.For asthma, healthcare professionals should carefully weigh the benefits against the potential risk of mental health side effects before prescribing the drug.