When methamphetamine enters the body, it produces significant increases in the levels of a neurotransmitting chemical in the central nervous system (brain and spinal cord) called norepinephrine or noradrenaline. Among its many functions, this chemical helps control normal function in the body’s arteries and veins, and when its levels rise, it produces a narrowing of these blood vessels that doctors commonly refer to as vasoconstriction. In turn, the presence of vasoconstriction increases the amount of pressure exerted on the walls of arteries located throughout the body, including the arteries found in and around the brain. The presence of methamphetamine in the bloodstream can also trigger a condition called vasculitis, which occurs when the immune system produces levels of inflammation that damage the integrity of these vessels. One of the potential consequences of vasculitis is a dangerous weakening of the artery walls.

Methamphetamine’s influence on artery health can lead to the formation of a common type of brain aneurysm called a berry aneurysm, according to a 2008 report by the University of Maryland School of Medicine. In addition, methamphetamine’s influence can cause a berry aneurysm to burst open and produce slow or rapid bleeding inside or outside the brain. Berry aneurysms get their name because they have a berry-like shape. Typically, they range in diameter from several millimeters to a centimeter or more; however, in some cases, unusually large berry aneurysms grow larger than two full centimeters in diameter. Depending on individual circumstances, an aneurysm in a methamphetamine user can burst open without warning, or rupture during the course of a toxic reaction to the drug commonly known as a methamphetamine overdose.