Aggression related to anabolic steroid use by teenagers may persist into young adulthood and be associated with longer-lasting, detrimental changes in brain chemistry, according to an article in the February issue of Behavioral Neuroscience. Researchers also found that aggression rose and fell in synchrony with neurotransmitter levels in the brain’s aggression control region.

American neuroscientists are deeply concerned about rising adolescent abuse of anabolic-androgenic steroids, given the National Institute on Drug Abuse’s estimate that roughly 500,000 teenagers abuse steroids each year. Not only are steroids associated with increased risk for heavier use of steroids and other drugs later in life, but long-term users can suffer from mood swings, hallucinations and paranoia; liver damage; hypertension; as well as increased risk of heart disease, stroke and some types of cancer. Withdrawal often brings depression, and recent research suggests that some anabolic steroids may be habit-forming.

Overseen by Richard Melloni Jr., PhD, of Northeastern University in Boston, the current study of 76 adolescent hamsters compared how individual hamsters behaved when another hamster was put into their cages. Normally mild-mannered hamsters still defended their turf, learning aggression during puberty by play-fighting, much like humans. Their roughhousing normally included wrestling and nibbling - pretty tame stuff.

However, hamsters injected with commonly used steroids (suspended in oil) became extremely aggressive. Even after the drug was withdrawn, the newly vicious hamsters attacked, bit and chased the intruders. In fact, their aggressiveness measured ten times greater than that of control hamsters injected with oil only. Their full-blown aggression lasted for nearly two weeks of withdrawal, the equivalent of half their adolescence. Eventually, the aggressiveness subsided; by three weeks of withdrawal, all the hamsters greeted intruders with normal, playful defensiveness.

Autopsy revealed that the outward aggressiveness correlated with changes in the brain. When the drugged hamsters were hostile hosts, the anterior hypothalamus secreted more vasopressin. By three weeks of withdrawal, vasopressin levels subsided in parallel with aggressive behavior. The anterior hypothalamus regulates aggression and social behavior. Thus, vasopressin - already known to stimulate that area - appears to fuel aggression.

The neuroscientists concluded that the aggressiveness triggered by anabolic steroids, although reversible, may last long enough to create serious behavioral problems for adults. Because this part of the rodent and human nervous systems is similar, researchers generalize their findings to humans. As a result, Melloni and his colleagues speculate that anabolic steroids can dramatically shorten teenage fuses and make young people more volatile for years, a danger to themselves and to others.

Melloni and others researchers also are concerned that drug use during a critical window in brain development can permanently change brain chemistry. He said, “Because the developing brain is more adaptable and pliable, steroids could change the trajectory if administered during development.” His lab is releasing other new findings, as yet unpublished, that the serotonin system - implicated in depression - may never recover.

“If you hit the right areas of the brain at the right time, you make permanent changes,” Melloni concluded from the converging evidence.

Finally, researchers such as Melloni hope these new insights can lead to treatments for aggressive behavior, with or without steroid abuse. “Linking aggression to fluctuations in vasopressin makes it an important neurotransmitter to target for pharmacotherapy,” he says.