The cannabis withdrawal items used in this study are in accordance with the proposed symptoms included in Criterion B of the upcoming DSM-5 cannabis withdrawal syndrome (see www.dsm5.org/ProposedRevision/Pages/proposed-revision.aspx?rid=430). All symptoms are shown in Table 2. Items assessing withdrawal were asked of those who reported a lifetime history of using cannabis 11 or more times and monthly use (when using the most) and had attempted cessation. For each item, participants were asked to indicate on a 4-point scale, ranging from ‘not at all’, ‘mildly’, ‘moderately’ to ‘severely’, how much they experienced that specific symptom after cutting down or going without using marijuana. An item was scored positive if it was experienced at least mildly. In accordance to the DSM-5 guideline, to meet criterion B of cannabis withdrawal, participants were required to endorse 3 symptoms or more. All other lifetime users, including those who had used cannabis less than 11 times, did not use monthly, did not attempt to quit or endorsed 1–2 symptoms were coded negatively.
