Teenagers who smoke marijuana heavily for a prolonged period of time could be damaging their brain structures that are crucial to memory and reasoning.

According to a study conducted by researchers at the Northwestern University in Chicago, chronic use of marijuana among teens and young adults can have debilitating effect on their brain. Heavy smokers experience changes in the so-called sub-cortical regions of the brain which are responsible for memory and reasoning.

The study was conducted on nearly 100 participants who were sorted into four groups: healthy people who never used pot, healthy people who used to be heavy pot smokers, people with schizophrenia who never used pot and schizophrenics who were former heavy pot users.

Healthy subjects who never smoked marijuana performed 37 times better on memory tests than healthy subjects who had smoked in the past while schizophrenics who never used pot scored nearly four times better than schizophrenic marijuana users.

"We observed that the shapes of brain structures related to short-term memory seemed to collapse inward or shrink in people who had a history of daily marijuana use when compared to healthy participants," said Matthew Smith, study author and assistant research professor in psychiatry and behavioral sciences at the Northwestern University Feinberg School of Medicine .

The result of the study, which was published Monday in the journal Schizophrenia Bulletin, also shows that marijuana users have brain structures that resemble those seen in schizophrenia patients.

According to Dr. John Csernansky, author of the study and chair of psychiatry and behavioral sciences at Northwestern University Feinberg School of Medicine and Northwestern Memorial Hospital, the abuse of popular street drugs such as marijuana may have dangerous implications for young people who are developing or have developed mental disorders. "This paper is among the first to reveal that the use of marijuana may contribute to the changes in brain structure that have been associated with having schizophrenia," he said.