Washington: The percentage of Americans who reported using marijuana more than doubled between 2002 and 2013, with nearly as large an increase in marijuana use disorders during that time period, a new study has found.
The research also showed that 2.5 per cent of adults - nearly 6 million people - experienced marijuana use disorder in 2012-13, while 6.3 per cent had met the diagnostic criteria for the disorder at some point in their lives.
The study, conducted by researchers from Columbia University and US National Institute on Alcohol Abuse and Alcoholism (NIAAA) found that marijuana use disorder is often associated with other substance use disorders, behavioural problems, and disability, and goes largely untreated.
The data was collected in the 2012-2013 wave of NIAAA's National Epidemiologic Survey on Alcohol and Related Conditions, the largest ever conducted on the co-occurrence of alcohol use, drug use, and related psychiatric conditions.
For this study, over 36,000 US adults were interviewed about alcohol, drug, and related psychiatric conditions.
The data showed that marijuana use disorder is about twice as common among men than women, that younger age groups are much more likely to experience the disorder than people aged 45 and over, and that those at the lowest income levels were at the highest risk.
This is the first national survey to use the diagnostic criteria from Diagnostic and Statistical Manual of Mental Disorders (DSM-5). In DSM-5, the old categories of marijuana dependence and abuse are combined into a single disorder.
To be diagnosed with the disorder, individuals must meet at least two of 11 symptoms that assess craving, withdrawal, lack of control, and negative effects on personal and professional responsibilities.
Severity of the disorder is rated as mild, moderate, or severe depending on the number of symptoms, researchers said. As the severity of marijuana use disorder increased, so did associated disability levels and frequency of marijuana use, they said.
In a previous study, Deborah Hasin from ColumbiaUniversity reported that three out of 10 marijuana users experienced marijuana abuse or dependence in 2012-13.
"An increasing number of American adults do not perceive marijuana use as harmful. While some can use marijuana without harms, other users do experience negative consequences, which can include mental and physical problems, and impaired functioning," she said.
Researchers found that only about 7 per cent of people with past-year marijuana use disorder receive any marijuana-specific treatment, and only about 14 per cent of people with lifetime marijuana use disorder receive treatment.
"These findings demonstrate that people with marijuana use disorder are vulnerable to other mental health disorders," said Nora D Volkow from National Institute of Drug Abuse (NIDA).
The findings were published in the American Journal of Psychiatry.
