Risk of narcolepsy in vaccinated against swine flu in 2009 was increased 17 times. In another study the risk was increased 4-9 times. Third study showed 14-16 times narcolepsy risk increase.
A similar Swedish study found increased psychiatric comorbidity in children and adolescents with narcolepsy.
A possible explanation of this phenomenon may be that the human antibodies to nucleoprotein cross-react with human hypocretin receptor.