Advantages of the study are also noted. The similarities between the full group and the subset suggested that withdrawal symptoms of cannabis were not being confused with other substances in the full group. First, the large and representative sample afforded a new vantage point on cannabis withdrawal. Further, the subset of respondents who did not abuse other substances provided an important opportunity to confirm that cannabis withdrawal symptoms reported by the larger group were not due to other substances they had used. Second, weighted factor analysis of the symptoms provided an organized quantitative method of arriving at a set of items that measured two aspects of cannabis withdrawal well. While replication of the factor structure is clearly needed, this study is the first to provide information from such analyses. Third, the measures included in the study enabled us to address important historical and psychiatric correlates of the two factors, contributing new and valuable information on clinical significance and associated aspects of psychiatric history.
