Despite the widespread use of cannabis, there has been relatively little research exploring patterns and correlates of use, abuse and dependence within genetically informative research designs. This study will supplement existing data from two ongoing studies of male (DA 12540, PI Madden) and female (AA 09022 PI Heath) twins by collecting comprehensive information on patterns of cannabis use, escalation in use and related harm from the twins' full siblings aged 18-30 (projected n =1,600). Combining data from these three sources will ensure adequate statistical power to address the following issues:
AIM 1 : To determine at what stages in the progression of cannabis use heritable influences first arise, by assessing the timing and onset of stages in the development of cannabis use disorders including: first exposure/opportunity to use; experimentation, escalating use, quantity used, the experience of first abuse/ dependence symptom and the onset of abuse or dependence.
AIM 2 : To assess subjective reactions to cannabis, the extent to which such responses are influenced by heritable factors, the extent to which such reactions may be correlated with risks for the development of cannabis use disorders and the extent of overlap in the genetic and environmental influences associated with subjective reactions to cannabis and those associated with liability to cannabis use disorders.
AIM 3 : To examine patterns of comorbid psychopathology (including other substance use/ dependence) associated with cannabis use/dependence and the extent to which qualitatively distinct heritable subtypes of cannabis use/dependence can be identified on the basis of comorbid psychopathology.
AIM 4 : To assess the psychometric properties of an assessment of cannabis use disorders (abuse, dependence) within the context of a genetically informative research design, and examine the genetic covariance structure of individual symptoms of abuse/dependence.
AIM 5 : Based on these analyses, to formulate a model for unfolding of genetic influences on transitions in cannabis and the emergence of dependence symptoms.
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