NEW YORK (Reuters) - People who get painful migraine headaches may be at a higher risk for developing clinical depression, suggests a new study from Canada. The research, published in the journal Headache, also hints that the relationship may go both ways, and people with clinical depression could have a higher risk of developing migraines, but that finding could have been due to chance, the researchers say. Nonetheless, lead author Geeta Modgill, who was at the University of Calgary while conducting the work, told Reuters Health that migraine and depression sufferers should know the signs of both ailments since each might be at a higher risk for the other condition. Migraines are throbbing headaches, sometimes on just one side of the head that can make a person nauseous and sensitive to light. At times they may be preceded by visual disturbances known as auras. Depression is a serious mental disorder defined by a collection of symptoms that can include sadness, insomnia, fatigue and emotional numbness. Modgills group pulled data from the Canadian National Population Health Survey, which profiled over 15,000 people and followed up with them every two years between 1994 and 2007. Overall, about 15 percent of the people in the study experienced depression and about 12 percent experienced migraines throughout the 12 years of the study. Cases of depression were significantly more common among people who had migraines at the beginning of the study - 22 percent of migraine sufferers got depressed, versus 14.6 percent of those who didnt have migraines. That made participants with migraines 80 percent more likely than people without the headaches to develop depression, and the link held up after adjusting for other influences like age and sex. People with depression were also 40 percent more likely than the non-depressed to develop migraines, but the relationship was not as robust. Also, the association disappeared when the data were adjusted for stress and childhood trauma. The researchers said childhood stress may change how a brain responds to stress later in life, and this type of study cannot tease out those biological effects. The study also cannot determine cause and effect for the link seen between depression and migraine.