Finding: Effects of drug abuse persist

Regular abusers of cocaine and amphetamines could continue to experience impaired brain function and slower bodily movement up to a year after abstaining from the drugs, research has found, writes Natasha Gilbert.

Rosemary Toomey and her team from the department of psychiatry at Harvard Medical School conducted a series of tests on subjects' attention, intelligence, memory and movement skills.

They found that users of these drugs had a deficit in their attention span and that they were slower in their actions compared with non-users, even after they had refrained from taking drugs for a year. "We don't know how long these deficits could continue," Dr Toomey told The THES .

But users did perform better on a visual vigilance test, which measures attentiveness to occasional pieces of information and is often used to evaluate air-traffic controllers. This same type of skill is impaired in those suffering from attention deficit hyperactivity disorder, where Ritalin (a stimulant) can improve performance.

Dr Toomey said that taking cocaine or amphetamines could enhance ability in this task and, as some cognitive impairments persisted after cessation of drug use, so might some advantages.

The researchers conducted the tests on 50 sets of twins, of which only one in each set had heavy stimulant abuse. The use of twins in the study allowed researchers to be sure as to whether deficits pre-dated drug use or were the consequence of drug taking.

Users took cocaine or amphetamines or both once a week for at least a year but were not dependent on the stimulants and did not seek treatment for their drug use.

Previous studies have examined the prolonged effects of stimulant abuse after six months of abstinence. But this is the first study to show that damage may persist for even longer periods.

These findings are published in the journal Archives of General Psychiatry .