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Influence of cannabis use trajectories, grade repetition and family background on the school-dropout rate at the age of 17 years in France.

BACKGROUND
Research has shown that cannabis use contributes to school dropout, but few studies have distinguished the age at onset of use from the age at progression to daily use neither their interaction with grade repetition.


METHODS
This study is based on a French representative cross-sectional survey (N = 29,393 teenagers aged 17 years) and uses retrospective data. The influence of drug-use patterns <16 years of age on school-dropout rates (5.3%) are modelled with logistic regressions among boys and girls.


RESULTS
The main factors associated with dropout were a low family socio-economic status, early grade repetition, single-parent families and daily tobacco smoking (ORa > or = 2.6). The link with the move to daily cannabis use was more evident when it occurred <14 years of age (ORa = 2.05 for boys and 3.41 for girls) rather than at > or =15 years (ORa = 1.45 for both sexes). The onset of cannabis use was not significant when occurring <14 years of age, but was linked to school attainment when occurring at age 15-16 years (ORa = 0.80 for boys and 0.64 for girls). Results are similar for alcohol use. Repeating a grade before beginning to use cannabis increased the dropout rates compared with the opposite sequence. Girls were more affected by early grade repetition and by early and daily cannabis use.


CONCLUSION
Cannabis use is rarely a trigger for grade repetition but can have either damaging or positive effects on school attainment depending of the level of use. Positive social competence reflected by peer initiation should be investigated to understand this paradoxical effect.