Withdrawal symptoms can result from quitting heavy marijuana use and belong in the American Psychiatric Association's (APA) manual of addictive and mental-health disorders, a Columbia University researcher says.

MedPage Today reported May 26 that researcher Deborah Hasin of Columbia's Mailman School of Public Health told attendees at an APA meeting in Toronto that the APA's Diagnostic and Statistical Manual (DSM-IV) should be updated to include "cannabis withdrawal syndrome." Hasin said the World Health Organization's International Classification of Diseases (ICD) should be similarly amended.

Hasin said that research has shown that heavy marijuana users who stop using can experience lethargy, insomnia, psychomotor retardation, anxiety, and depression.

Other researchers said that the symptoms do not add up to true withdrawal, but rather may constitute a "rebound effect" or part of a preexisting condition. Nicholas Seivewright, M.D., a consultant psychiatrist with the Community Health Sheffield NHS Trust in Great Britain, said marijuana users would have to experience novel symptoms they had not had before to be properly labeled as suffering from withdrawal.