Can montelukast (Singulair) cause increased impulsivity and other behavioral problems in a 6-year-old child?

Montelukast and Behavioral Concerns in a 6-Year-Old

Yes, montelukast can significantly increase behavioral concerns and impulsivity in a 6-year-old child, and the FDA has issued a Boxed Warning specifically about these serious neuropsychiatric risks. 1

FDA Boxed Warning and Drug Label Information

The FDA drug label for montelukast explicitly warns about serious neuropsychiatric symptoms that can occur during treatment or even after stopping the medication, affecting patients with or without prior mental health history 1. The label specifically instructs:

• Discontinue montelukast immediately if unusual changes in behavior or thinking occur 1
• Monitor for agitation, aggressive behavior, attention problems, anxiety, irritability, depression, hallucinations, obsessive-compulsive symptoms, sleep disturbances, suicidal thoughts, and uncontrolled muscle movements 1
• These events can happen in children as young as 6 months of age 1

Clinical Trial and Real-World Evidence

Conflicting Evidence on Risk Magnitude

The evidence presents a complex picture with contradictory findings:

Studies showing increased risk:

• A 2024 Korean population study of 161,386 pediatric patients found significantly increased risk of neuropsychiatric adverse events across all time windows, with adjusted odds ratios ranging from 1.21 to 1.38 2
• A 2025 Turkish cohort study of 1,163 children showed neuropsychiatric symptoms increased from 14.8% to 34.3% after one month of montelukast treatment, with significant increases in insomnia, nightmares, behavioral problems, irritability, agitation, anxiety, and hyperactivity 3
• A 2022 retrospective study of 385 children reported 31.9% experienced adverse drug reactions, with sleep disturbance (15.1%), agitation (10.4%), and hyperactivity (6.8%) being most common 4

Studies showing no increased risk:

• A 2025 Swedish nationwide study of 74,291 children found no association between montelukast use and neuropsychiatric adverse events compared to long-acting β-agonists (HR 0.99,95% CI 0.84-1.16) 5
• A 2022 prospective controlled study of 95 asthmatic preschoolers found no difference in behavioral problem scores between montelukast and inhaled corticosteroid groups 6

Prioritizing the Most Recent High-Quality Evidence

Given the conflicting evidence, I prioritize the FDA Boxed Warning 1 and the most recent 2025 Turkish cohort study 3, which showed a dramatic increase in neuropsychiatric symptoms (14.8% to 34.3%). This study is particularly relevant as it prospectively followed children with direct caregiver reporting of symptoms before and after treatment initiation.

Clinical Recommendation Algorithm

For a 6-year-old currently on montelukast:

1. Immediately assess for any behavioral changes, impulsivity, sleep disturbances, mood changes, or attention problems that have emerged since starting montelukast 1

2. If ANY neuropsychiatric symptoms are present:

   • Discontinue montelukast immediately 1
   • Switch to inhaled corticosteroids as the preferred alternative therapy 7
   • Monitor for symptom resolution over 2-4 weeks

3. If no symptoms are currently present:

   • Consider whether montelukast is truly necessary, as inhaled corticosteroids are the preferred first-line therapy for persistent asthma in this age group 7
   • If continuing montelukast, counsel parents to monitor closely for behavioral changes, impulsivity, sleep problems, agitation, anxiety, or mood changes 1
   • Schedule close follow-up within 2-4 weeks 3

4. For new prescriptions in 6-year-olds:

   • Montelukast should only be considered as an alternative when inhaled corticosteroids cannot be used 7
   • The 2020 NAEPP guidelines note that montelukast has limited availability considerations following the FDA Boxed Warning 7

Important Clinical Caveats

• Age matters: Younger children appear at higher risk, with preschool and early school-age children (4-9 years) showing the highest prevalence of adverse reactions 4
• Concomitant antihistamines may increase risk of neuropsychiatric symptoms 3
• Symptom onset timing: Neuropsychiatric effects can occur within days to weeks of starting treatment, with increased risk persisting throughout the treatment period 2
• Serious events are possible: While rare, severe reactions including hallucinations have been reported even in young children 6
• Symptoms may persist after discontinuation: The FDA label warns that neuropsychiatric problems can occur even after stopping the medication 1

Preferred Alternative Treatment

Inhaled corticosteroids remain the preferred controller medication for persistent asthma in 6-year-olds, with montelukast relegated to alternative therapy status specifically due to the FDA Boxed Warning 7. For step 2 therapy in this age group, low-dose inhaled corticosteroids are preferred over montelukast 7.