As of 2009, the incidence of recorded death or life-threatening diseases associated with anabolic steroids use is relatively low. Most severe problems are anecdotal and have been linked to long-term and high-dose use. It is possible that for most people, the side effects of anabolic steroid use appear to be minimal.
Many changes in the body may return to normal after steroid use is stopped. On the other hand, there is enough data to conclude that there is at least an association between steroid use and significant negative side effects.
Anabolic steroids seem to increase the risk of elevated blood pressure, cardiovascular disease, high cholesterol levels, or coronary artery disease. Even if these changes are temporary, steroid users are exposing themselves to the premature development of vascular and coronary heart disease.
Some studies imply that steroids can even change the structure of the heart, impairing its contraction and relaxation. Possible effects of these alterations in the heart are hypertension, irregular heartbeat, congestive heart failure, and heart attacks.
These changes also occur in non-steroid-using athletes, but anabolic steroid use may accelerate this process. However, all these findings have been disputed.
High doses of oral anabolic steroid compounds may cause liver damage. The liver is the main organ that breaks down steroids in the digestive system. Many studies of steroid users have documented abnormalities in liver function tests. However, the seriousness of these abnormalities and their duration is still disputed.
Less seriously, acne is common among anabolic steroid users, caused by increased testosterone levels. The conversion of testosterone can also accelerate the rate of premature baldness for those who are genetically predisposed.
There are also some gender-specific side effects of anabolic steroids. Males may develop breast tissue (known as gynecomastia), temporary infertility (although sexual drive might actually increase), and testicular atrophy. Steroid use may also be linked with prostate cancer. Female-specific side effects include increases in body hair, deepening of the voice, and enlarged genitals. When taken during pregnancy, anabolic steroids can affect fetal development.
One area where there is almost no debate is the negative effect of anabolic steroids on still-growing adolescent users. For adolescents, steroid use may halt bone growth and result in stunted growth. Other effects include accelerated bone maturation and premature sexual development. These side effects are particularly dangerous because teenagers are more likely than adults to use anabolic steroids in dangerously high dosages and without any medical supervision.
On a comparative scale, however, anabolic steroids are less dangerous than most common drugs. In 2007, a group of scientists attempted to create a new ranking system by assessing twenty different drugs based on their potential for addiction and the harm they do to the individual and to society. The experts rated heroin as the most dangerous drug, followed by cocaine and barbiturates. Anabolic steroids only ranked sixteenth out of twenty, far below alcohol and tobacco.
However, the long-term consequences of steroid use have not been well investigated. It is possible that more severe side effects will occur later in the life of anabolic steroid users.
Sterngass Jon, Controversy! Steroids, 2011
Duchaine Daniel, Underground Steroid Handbook II, 2006
Hart Mick, Laymans Guides to Steroids
Hart Mick, Laymans Guides II - Return of the Syringe
Hart Mick, Laymans Guides III - Return of the Syringe
Hardcore, Complete Steroid Handbook, 2004