From the article:
Researchers have confirmed three gene changes that raise the risk that a blood vessel in the brain will weaken and balloon out (aneurysm), creating a life-threatening chance of rupture. Smoking, the biggest risk factor for brain aneurysm, is five times more dangerous in people with these gene variations. However, a second study on the same population notes that most people with aneurysm die of cancer or heart problems.
In one study (Broderick, abstract 156), researchers found that the chance of an intracranial aneurysm increased between 37 percent and 48 percent for people who carried one copy of an identified risky gene variation. However, when the gene variant was combined with smoking the equivalent of one pack a day for 20 years, the risk increased more than five-fold. People with two copies of the gene variant were at even higher risk.