Dirty games with the mind

A new study on the connection between marijuana abuse and human cognition throws more light on the long-term effects of drug addiction

Published: Saturday 15 June 1996

-- (Credit: Vishwajyoti)GET high on marijuana and remain low in cognition. Impairment in mental flexibility and abstraction are some of the long-term effects of the drug that otherwise gives what the addicts term as a pleasureable kick. Immensely popular with a section of the youth, marijuana has remained low on the priority of researchers. The recent finding on the long-term effects of the drug is, thus, a heartening sign.

Determined to spread awareness regarding the adverse effects of marijuana, scientists at the Harvard Medical School at Boston, us, set out to analyse its effects on human cognition. Though it is well known that the target organ of marijuana is the brain, misinformation regarding the drug's disastrous effects prevail.

Harrison G Pope and Deborah y Todd studied a sample of college students hooked on to the drug. A rigorously supervised, 19-hour abstinence period was observed before testing. This was to ensure that test results were unaffected by recent use of the drug. Thereafter, a series of neuropsychological tests were undertaken to assess general intellectual functioning, abstraction ability, sustained attention, verbal fluency, and the ability to learn and recall new verbal and visuo-spatial information.

Researchers found that heavy marijuana use holds mental faculties to ran- som. It induces alterations in brain functioning which outlast the direct effects due to presence of the drug in the brain. However, scientists do not rule out the effects of the drug- residue that lingers in the brain after acute intoxication has subsided.

The extent of addiction has also a bearing on the damage the brain undergoes. "Frequent marijuana users, relative to less frequent users, show impairments in mental flexibility and abstraction," report researchers.

Though this study has conclusively proved the adverse effects of the drug on human brain, it has not been able to localise the regions of brain the drug attacks. There have been attempts in the past to detect changes in brain function- ing using neuroim1!ging techniques. But with the limited sensitivity of the avail- able techniques, success had remained elusive.

Now that neuroimaging technologies, like positron emission tomography, have attained remarkable sophistication, such studies can be conducted with great accuracy. By achieving high- resolution measurements of regional brain activity during the performance of varying cognitive tests, doctors are expected to zero-in on those areas as well. (JAMA, Vo1275, No 7).

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