U.S. government researchers have found that a widely prescribed asthma drug originally sold by Merck & Co, may be linked to serious mental health problems for some patients, according to a scientific presentation reviewed by Reuters. The researchers found that the drug, sold under the brand name Singulair and generically as montelukast, attaches to multiple brain receptors critical to psychiatric functioning. By 2019, thousands of reports of neuropsychiatric episodes, including dozens of suicides, in patients prescribed the drug had piled up on internet forums and in the U.S. Food and Drug Administration's tracking system. Such "adverse event" reports do not prove a causal link between a medicine and a side effect, but are used by the FDA to determine whether more study of a drug's risks are warranted. The reports and new scientific research led the FDA in 2020 to add a black box" warning to the montelukast prescribing label, flagging serious mental health risks like suicidal thinking or actions. The behavior of montelukast appears similar to other drugs known to have neuropsychiatric effects, such as the antipsychotic risperidone. When the FDA added the black box, it cited research from Julia Marschallinger and Ludwig Aigner. The two scientists told Reuters ... the new data showed significant quantities of montelukast present in the brain. The receptors involved play a role in governing mood, impulse control, cognition and sleep, among other functions, they said.