Unanticipated Pathological Laughter Following Atomoxetine Administration in a Child With Autism Spectrum Disorder and Attention-Deficit/Hyperactivity Disorder.

A 6-year-old boy with autism and ADHD started taking atomoxetine (a medication for attention problems) and developed unusual episodes of uncontrollable laughter. These episodes happened frequently for about 10 days, then stopped on their own while he continued the medication. After this period, his attention and social skills actually improved. When his dose was increased later, the laughter didn't return.

This suggests the laughter was a rare, temporary side effect that resolved without stopping the helpful medication.

This case report describes a 6-year-old boy with autism spectrum disorder and ADHD who developed unexpected pathological laughter after starting atomoxetine (5 mg/day). The child experienced frequent, spontaneous laughter episodes lasting 2-5 minutes without emotional triggers, beginning within 5 days of medication initiation. These episodes resolved within 10 days despite continued atomoxetine treatment, coinciding with a minor increase in risperidone dosage. Subsequently, the child showed improvements in attention, eye contact, and cooperation.

When atomoxetine was later increased to 10 mg/day, no pathological laughter recurred. The authors suggest this may be a rare, temporary side effect requiring clinical vigilance, particularly in children with neurodevelopmental disorders and family history of mood disorders.

Clinicians should monitor for mood-related side effects when prescribing atomoxetine to children with neurodevelopmental disorders, particularly those with family history of mood disorders. The temporary nature of this side effect suggests continued treatment may be appropriate with careful monitoring rather than immediate discontinuation.

Single case report with no control group or systematic investigation. Cannot establish causation or frequency of this side effect. Confounding factors include concurrent medications (risperidone, clonidine) and natural developmental changes. Limited generalizability to other children with similar conditions.

Atomoxetine, a selective norepinephrine reuptake inhibitor (NRI), is commonly prescribed for attention-deficit/hyperactivity disorder (ADHD) and has shown effectiveness in children with autism spectrum disorder (ASD). Although mood disturbances and psychiatric symptoms are recognized side effects, pathological laughter has not been previously reported. We present the case of a 6-year-old boy diagnosed with both ASD and ADHD who developed sudden, uncontrollable episodes of pathological laughter after beginning low-dose atomoxetine (5 mg/day, ~0.25 mg/kg). The child had a history of hyperactivity and aggression, managed with risperidone and clonidine.

Within 5 days of initiating atomoxetine, he exhibited frequent, spontaneous laughter lasting 2-5 min without any apparent emotional trigger. These episodes resolved within 10 days despite continued atomoxetine treatment, coinciding with a minor increase in risperidone dosage. Following this period, the child displayed noticeable improvements in attention, eye contact, and overall cooperation. Atomoxetine was later increased to 10 mg/day, with no recurrence of pathological laughter.

This case suggests that pathological laughter may be a rare but temporary side effect of atomoxetine, even at low doses. Given the child's familial history of bipolar disorder and the influence of catecholamines on mood regulation, clinicians should be vigilant in monitoring mood-related side effects in children with neurodevelopmental disorders. This report emphasizes the need for personalized treatment approaches and further investigation into the mechanisms and risk factors underlying this phenomenon.