Study: Heavy pot use causes false memories

WASHINGTON – Although marijuana is now legal in a few states and D.C., the drug still poses dangers: A new study found that smoking a lot of pot can produce false memories.

A study published in the journal Molecular Psychiatry finds that chronic consumers of cannabis may be more prone to experiencing false memories compared to nonsmokers.

Researchers say memory mistakes related to childhood situations are common to everyone, because the memory of events over time can be influenced by different retellings of events from many people. But it’s much easier, they say, for pot smokers to develop imaginary or false memories.

The study compared healthy nonsmokers of pot with chronic users who’d quit smoking pot for one month before the study. Subjects were told to remember a list of words, which were taken away after a few minutes, then given a second list of words, then asked to identify which words were on both lists.

The pot smokers were more likely than the nonsmokers to remember words as being on the first list that weren’t there. The words did, however, happen to be related to words on that first list.

The study also used magnetic resonance imaging (MRIs) to examine each participant’s hippocampus — the part of the brain related to memory and cognitive functions.

Those images reveal the hippocampi of non-pot smokers light up significantly more than those of pot users. And the longer participants had smoked pot throughout their lives, the less activity scientists found.

WTOP’s Kristi King contributed to this report.

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