Does cannabis onset trigger cocaine onset? A case-crossover approach.

Area of Science:

• Psychiatry
• Epidemiology
• Addiction Research

Background:

• Discordant co-twin designs are common in psychiatric research to control for genetic influence.
• The case-crossover design offers an alternative for estimating exposure-associated disease risk, particularly in psychiatric studies.
• This design utilizes a "subject-as-own-control" approach to minimize confounding from stable individual characteristics.

Purpose of the Study:

• To investigate if cannabis onset acts as a proximal trigger for cocaine use.
• To apply the case-crossover epidemiologic research design in a psychiatric context.
• To control for genetic influences and other antecedent characteristics of drug users.

Main Methods:

• Utilized the case-crossover epidemiologic research design.
• Analyzed data from newly incident cocaine users from the 2002-2006 US National Surveys on Drug Use and Health.
• Employed a "subject-as-own-control" framework to hold constant individual traits.

Main Results:

• Identified 48 cocaine users with both cannabis and cocaine onset in the same month-long hazard interval.
• The observed number of users (48) exceeded the expected value (30) based on the pre-specified control interval.
• Estimated relative risk (RR) for cannabis onset preceding cocaine use was 1.6 (exact mid-p = 0.042).

Conclusions:

• The findings support the hypothesis that cannabis onset is a proximal trigger for cocaine use.
• The case-crossover design effectively controlled for genetic influences and other stable individual factors.
• This research highlights the utility of the case-crossover design in psychiatric and addiction research.