Over half of influenza patients in Japan showing abnormal behavior had taken the med, but health authorities say it’s not clear if there was a causal link, according to a new government report, Reuters reports. Japan is investigating whether there is any link between Roche’s Tamiflu and neuropsychiatric problems after more than 100 mostly young people showed erratic behavior such as jumping from buildings after taking the drug. There have been eight cases of deaths after abnormal or possibly abnormal behavior.

The Health Ministry report said that of 137 patients who had shown abnormal behavior, 82 had taken Tamiflu, while 52 had not. But the report, compiled by a group of doctors and other health experts, said their figures were difficult to assess because it was not clear what percentage of all influenza patients had been prescribed Tamiflu. The report also said that the number of patients showing abnormal behavior did not drop after the government warned in March against prescribing Tamiflu to those aged 10 to 19.

A Health Ministry official says the study had been inconclusive but that a separate group of doctors and experts would present their own study later in the month. “We hope to reach some kind of conclusion at that time,” he tells Reuters. An FDA panel, meanwhile, recently recommended stronger psychiatric warnings.

Roche and its Japanese partner Chugai Pharmaceutical Co maintain there is no causal relationship has been established between Tamiflu and neuropsychiatric symptoms, and doctors say influenza itself can cause abnormal behavior. Tamiflu, known generically as oseltamivir, is widely prescribed in Japan. Chugai estimates some 35 million people have taken the drug, accounting for around 70 percent of the world’s Tamiflu consumption.