1 Concurrent and Simultaneous Polydrug Use 2 involving Cannabis and Tobacco and its relationship 3 with the Academic Achievement amongst University 4 Students 5

The combined use of cannabis and tobacco is frequent in Europe. Few studies have 16 nonetheless explored this pattern of consumption and its relationship with the academic 17 achievement in Spanish population. The aim of the present study was to analyze: (1) the frequency 18 of four patterns of polydrug use the last year of cannabis and tobacco (non-dual users of cannabis 19 and tobacco; concurrent users: cannabis and tobacco separately; simultaneous users: tobacco in 20 cannabis joints; simultaneous users: tobacco in cannabis joints alongside with alcohol) by gender 21 and age; (2) the grade point average (GPA) by gender and age and; (3) the association between the 22 frequency of the four patterns of use and the GPA amongst a sample of 477 Spanish university 23 students. The use of cannabis and tobacco (concurrent and simultaneous) and the GPA were 24 assessed by means of self-reported questionnaires. Statistically significant differences were found 25 for the GPA with respect to gender. The GPA by the non-dual users of cannabis and tobacco was 26 significantly higher than the GPA corresponding to the concurrent and simultaneous users. The 27 combined use of cannabis and tobacco, regardless of the type of use (concurrent or simultaneous), 28 is strongly related to poor academic achievement amongst university students. 29