Science Daily — Parents, doctors, and others have wondered whether common treatments for attention-deficit hyperactivity disorder (ADHD) inadvertently predispose adolescents to future drug abuse. The answer may depend on the age at which treatment is started and how long it lasts, say the authors of a new brain-imaging and behavioral study conducted in animals at the U.S. Department of Energy's Brookhaven National Laboratory.
"Our study shows that the brain's reward pathways are definitely influenced by methylphenidate, one of the stimulant drugs commonly used to treat ADHD," said Brookhaven researcher Panayotis (Peter) Thanos, lead author of the study. "But the brain chemistry changes we observed suggest that the developmental stage at which treatment begins and the duration of treatment are important variables that need further study."
In the study, rats were given methylphenidate mixed with distilled water beginning one month after birth -- early adolescence for rats. Animals received either 1 or 2 milligrams methylphenidate per kilogram of body weight, consistent with clinical doses given to children with ADHD. A control group of rats was handled under identical conditions but given plain water.
After two months of treatment, and again after eight months, the scientists performed positron emission tomography (PET) scans to measure the levels of dopamine D2 receptors, a type of brain receptor important for experiencing reward and pleasure that has been linked to pleasure and drug abuse. After the eight-month treatment, animals were also tested for their propensity to self-administer cocaine. Read the article on Science Daily