Three hundred twenty-four cases and 647 controls were 10 years of age or older and half were male (median age for cases was 34.0 years and 33.5 years for controls). Most cases were identified at their epilepsy diagnosis (57.7%). Partial-onset seizures occurred in 36.4% of cases and most had unknown etiology. Major depression mainly occurred in the absence of migraine (59.0% in cases, 70.8% in controls) as did suicide attempt (52.4% in cases, 66.7% in controls). MA accounted for 71.4% of migraine in cases and 46.7% in controls (p=0.005).
Among controls, the lifetime prevalence of MA was 7.6% and the lifetime prevalence of depression was 7.4%. In accordance with prior studies (9), major depression was 2.1-fold more common in controls with MA than in those without MA (14.3% vs. 6.9%, p=0.06). MA, major depression and suicide attempt together occurred in 6 cases and 2 controls.
1.3.1 Major depression and MA
The risk for developing an unprovoked seizure was increased more in the presence of both MA and major depression, then in the presence of either condition alone (). The pattern of results was similar in subanalyses of children, adults, females, generalized seizures, and seizures of unknown cause (data not shown).
Association between migraine with aura, major depression, suicide attempt and incident unprovoked seizures in Icelandic children and adults aged 10 years and over
1.3.2 Suicide attempt and MA
The risk for developing an unprovoked seizure was increased most in the presence of both MA and suicide attempt, and was greater than the increased risk associated with suicide attempt alone or with MA alone. Adjustment for cumulative alcohol intake and major depression did not change the results. A similar pattern was seen in subanalyses conducted in adults and in children, although few suicide attempts occurred in children.
1.3.3 Number of conditions
Three conditions considered were major depression, suicide attempt and MA. The risk of an unprovoked seizure was increased 2.0-fold with any one condition (95% CI=1.4-3.0), 4.9-fold with any two conditions (95% CI=1.7-13.9), and 6.7 with all three conditions (95% CI=1.3-33.4). The test for linear trend was statistically significant.
1.3.4 Associations in cases and in controls
Further analyses were conducted separately in cases and in controls to examine the association between depression and/or suicide attempt and MA. Depression and/or suicide attempt was associated with a non-significant 2.1-fold increase in MA among controls (95% CI=0.9-5.1) and with a significant 3.3-fold increase in MA for cases (95% CI=1.7-6.5).