A new study from the Howard Florey Institute in Melbourne may help explain why people who experimented with amphetamines, such as 'speed', as teenagers are more likely to become addicted and more susceptible to heart attack following re-use of the drug as adults.
Dr Andrew Lawrence and PhD student Cameron McPherson have discovered that adolescent rats exposed to a small dose of amphetamine have increased sensitisation to the drug when it is re-administered to them as adults.
Alarmingly, they also found that with this pattern of drug-taking behaviour, adult rats became possibly more susceptible to heart attack following the re-use of amphetamines.
Dr Lawrence said this behavioural model accurately mimics a common pattern of human drug-taking behaviour.
"Although many teenagers experiment with drugs, most don't become regular users, but may try the drug later again as adults.
"A teenager's early experimentation might be minor, but it can still have a damaging effect on their developing brain.
"We found that when a teenage rat is given amphetamines, and then after abstinence has the drug again as an adult, they have a more sensitised reaction, opening the door for addiction.
"As well as activating the brain's reward system, which is involved in addiction, amphetamine also affects brain regions that control heartbeat, blood pressure and temperature.
"By effecting basic brain functions, amphetamine may expose experimenting teenagers to an increased risk of heart attack if they re-use the drug later in life," he said.
Other studies have looked at the effects of drug use exclusively in adolescents or adults, but Dr Lawrence's research is the first to examine both life stages with a significant period of abstinence from the drug in between.
The period between the first drug exposure as an adolescent and then as an adult is long enough to rule out any withdrawal or previous addictive reactions.