An aneurysm is an abnormal swelling or bulge in the wall of a blood vessel, such as an artery. It begins as a weak spot in the blood vessel wall, which balloons out of shape over time by the force of the pumping blood. Aneurysms can occur anywhere throughout the circulatory system, but most commonly develop along the aorta (the body’s main artery that runs the length of the trunk from the heart) and in blood vessels of the brain. The exact cause of an aneurysm is not always clear, but there are several factors that can increase the risk of developing one, including:

• Congenital: a weakness in the blood vessel wall that is present from birth.
• High blood pressure: hypertension over many years.
• Atherosclerosis: narrowing of the arteries.
• Family history: having a first-degree relative, such as a parent, brother, or sister, with a history of a brain aneurysm may make you more likely to develop one than someone with no family history of the condition.
• Smoking: smoking is a risk factor for brain aneurysms to form and for brain aneurysms to rupture.
• Age: your risk of developing a brain aneurysm increases as you get older, with most cases diagnosed in people over the age of 40.
• Gender: abdominal aortic aneurysms occur most often in people who are assigned male at birth.
• Drug use: drug use, particularly using cocaine, raises blood pressure and can lead to an infection that causes a mycotic aneurysm.
• Head trauma: a brain aneurysm can develop after a severe head injury if the blood vessels in the brain are damaged, although this is very rare.

It is important to note that an aneurysm may have no symptoms until it is either very large or it ruptures. Symptoms depend on which blood vessel is affected. If you have any concerns about your risk of developing an aneurysm, you should speak to your doctor.