Screening and assessment of cannabis use

Ask all new patients routinely and others (adolescents and adults) opportunistically and periodically about cannabis use (including prescribed medicinal cannabinoids), as part of a general screen for disorders of substance use and gambling; these disorders are common (and often co-exist) and people are reluctant to disclose them, often due to fear of stigma. Screening and assessment of substance use and addictive behaviours outlines history-taking (including use of the ASSIST-Lite tool), examination, and investigations that should be considered in a broad review of substance use and addictive behaviour.

Useful information to gather on cannabis use includes:

  • frequency of use (and of tobacco use, because co-dependence is common)Zvolensky, 2020
  • factors that precipitate or perpetuate use
  • previous efforts to cut down (including severity of any withdrawal effects)
  • whether the person or others are concerned about their current use
  • potential harms (including neglect of life activities and relationships).

Questionnaires that can be used to gauge the severity of cannabis use include the 5-item Severity of Dependence Scale (SDS), and the 8-item Cannabis Use Disorder Identification Test (CUDIT-R).

Common symptoms of cannabis withdrawal include insomnia, tremor, reduced appetite, irritability and anxiety. Intensity and time course vary considerably between individuals, but symptoms generally start within 1 day of stopping, peak in 2 to 3 days and resolve over 2 to 3 weeksBonnet, 2017. Although some individuals experience anger, aggression seems most common in those with a previous history of this behaviourSmith, 2013. Cravings and sleep disturbance can persist for months. Past experience of withdrawal symptoms, and severity of dependence are key determinants of the likely severity of a planned withdrawal, which can be explored by asking ‘What happened when you last tried to cut down?’Allsop, 2011.

To identify people who require specialist referral or inpatient withdrawal, ask about the factors that determine safety of the withdrawal setting for the person and those around them.

Assessment of mental health is important, as psychiatric comorbidities are common among people who use cannabis; see Mental illness considerations in substance use and addictive behaviours.