Cluster headache causes extreme pain, but its origins remain unclear. New research links the disorder to genetics, inflammation, and tobacco smoke exposure.

Unlike an ordinary headache, a cluster attack typically erupts without warning and causes excruciating pain around one eye. Episodes can last from 15 minutes to three hours and often return at similar times each day. The severity of the condition has led to its troubling nickname, the “suicide headache.”

Scientists have long suspected that both genes and environmental exposures contribute to cluster headaches. Two studies from Karolinska Institutet in Sweden have now examined those influences from different angles, revealing signs of inflammation, altered gene regulation, and increased exposure to toxic substances.