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The more severe a person's marijuana withdrawal symptoms when they quit using the drug, the bigger the effect on their functional ability and the more likely they were to start using again, results of an Australian study showed.

Participants' withdrawal-induced functional impairment in normal daily activities was significantly associated with the severity of withdrawal symptoms (P=0.0001), severity of cannabis dependence (P=0.03), and time spent abstaining from pot smoking (P=0.004), according to David Allsop, PhD, of the University of New South Wales in Sydney, Australia, and colleagues.

Those who experienced more severe impairment were also significantly more likely to relapse at follow-up (P=0.001), Allsop and co-authors wrote online in PLoS One.

"Questions over the clinical significance of cannabis withdrawal have hindered its inclusion as a discrete cannabis induced psychiatric condition in the Diagnostic and Statistical Manual of Mental Disorders (DSM IV)," the authors explained.

They set out to "quantify functional impairment to normal daily activities from cannabis withdrawal" and what factors predicted impairment in a 46-participant sample of nonclinical, nontreatment-seeking Australian adults.

Participants smoked 5 or more days a week, had marijuana dependence, had experienced one or more withdrawal symptoms related to pot smoking, and were asked to quit smoking for 2 weeks.

The researchers analyzed whether the severity of functional impairment during the 2-week abstinence period was predicted by the severity of dependence or the amount used, the relationship between intensity of withdrawal symptoms and functional impairment, relapse associations with levels of functional impairment and/or withdrawal symptoms, and what factors -- if any -- predicted time to relapse.

The authors collected demographic and cannabis dependency information at baseline. Dependency was established through the Severity of Dependence Scale, a five-item, four-point scale.

Participants were given a 1-week "smoking as usual" period, followed by a 2-week abstinence period, and a follow-up at 1 month. Each day during the 3-week span of use and abstinence, they filled out a Cannabis Withdrawal Scale online, which provided a scaled rating of 19 withdrawal symptoms.

During abstinence from cannabis, participants underwent some psychological interventions and were paid a total of about $467 for adhering to the study protocol. They had to submit urine samples during the 2 weeks of abstinence.

Participants were also evaluated in-person at baseline, at the end of the "smoking as usual" week, at weeks 1 and 2 of abstinence, and at follow-up.

Those who relapsed -- established via self report or urine test -- during the first week of abstinence were offered a chance to restart the abstinence attempt. The researchers discarded withdrawal data for those who relapsed during the second week but retained all functional impairment data.

Of the 46 participants, 10 smoked during the 2-week intervention at a mean 5 days after starting the abstinence period, "which coincided with peak functional impairment," they wrote.

The authors noted that the "strongest predictor of functional impairment to normal daily activities from cannabis withdrawal was the severity of the cannabis withdrawal symptoms" (P=0.0001).

Time was also a significant factor in predicting functional impairment (P=0.004) and, in participants who relapsed, was associated with six withdrawal symptoms, and had a nonsignificant association with a seventh, including:

• Trouble sleeping (P=0.008)
• Lack of appetite (P=0.01)
• Feelings of anxiety (P=0.01)
• Feeling like "life was an uphill struggle" (P=0.01)
• Feeling of physical tension (P=0.03)
• Mood swings (P=0.04)
• Depression (P=0.05)

Higher dependency scores were also significantly predictive of functional impairment (P=0.03).

The researchers also reported that higher functional impairment during the abstinence period was associated with higher levels of cannabis use at 1-month follow-up (P=0.001), even after adjustment for baseline use (P=0.029) and dependency scale scores (P=0.001).

"It is of note that the average level of functional impairment caused by cannabis withdrawal symptoms was relatively mild ... among this sample of nontreatment-seeking users," wrote Allsop and colleagues, adding that scores were based on self-perception of impact and that higher levels of withdrawal may be expected in patients seeking treatment.

However, they concluded that the symptoms were "clinically significant because [withdrawal] is associated with elevated functional impairment" that became more severe as withdrawal symptoms grew in severity.

The authors speculated that because lower levels of marijuana use were associated with lower levels of withdrawal-related impairment, that "stepped reductions in cannabis use prior to a quit attempt could reduce dependence, and thus reduce levels of withdrawal related to functional impairment, improving chances of achieving and maintaining abstinence."

The study was limited by a small sample size, nontreatment seeking population, and lack of external support for self-reported impairment.

The findings need to be replicated in clinical samples, but "tailoring treatments to target withdrawal symptoms contributing to functional impairment during a quit attempt may improve treatment outcome," the authors concluded.

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