The largest early clinical study of cannabis effects, a study of 53 men hospitalized for 21–42 days, indicated that in the week following cessation of cannabis use, symptoms commonly reported included sleep disturbance (89%), restlessness (89%), and irritability (62%).9 In more recent prospective outpatient and inpatient studies, 13–18 no cannabis withdrawal symptom emerged in all studies. However, symptoms commonly reported were anxiety (after low dose13) 14, 16, 18 and symptoms of physical discomfort. 16–18 Irritability was also commonly found, 13–18 although in one study 13 only in the low consumption condition; in a second study 14 only in the high consumption condition; and in a third study, evidence was only “moderate.”17 The anxiety/depression withdrawal symptoms found in these studies corresponded well to our second factor, providing important consistency between this large general population sample and previous prospective outpatient and inpatient studies. Weakness withdrawal symptoms were also found in lab studies 13, 14 and in a clinical study of adolescents, especially males. 20 While fatigue was not found during cannabis withdrawal among cannabis users in their home environments, 17 the other
