Our results confirm previous studies, which have shown support for an association between cannabis involvement and STB (e.g., Fergusson et al., 2002; Moore et al., 2007; Pedersen, 2008). In addition, unlike some other studies, associations in our sample were not explained by confounding measures (Price et al., 2009; Wilcox et al., 2010). Differences between our study and others may be related to sample characteristics, measurement of ideation/attempt, or the possible inclusion or exclusion of certain covariates. To identify potential contributions of differences in measurement we differentiated SI by duration (>1 day) but associations with cannabis involvement did not vary. In contrast, we did show a difference between suicide attempts with and without a plan: cannabis involvement was related to SANP only, confirming previous studies on number of substances used (Borges et al., 2000) and alcohol dependence (Conner et al., 2007). Even though SANPs are found to be less likely to result in completed suicide (Harriss et al., 2005), suicidal attempts, in and of themselves are amongst the leading contributors to economic burden (Palmer et al., 1995) and are powerful predictors of later completed suicide (Harris and Barraclough, 1997; Suominen et al., 2004), emphasizing the need for effective prevention strategies.
