Chunk #15 — 2. Method — 2.1 Background information – twin studies and cannabis phenotypes — 2.1.2 Phenotypes: initiation of cannabis use and problematic use
The other phenotype we examine, problematic cannabis use, is less consistently defined. Different definitions of problematic cannabis use can be found in the literature, ranging from symptoms of abuse to a full dependence diagnosis. Most studies use abuse and dependence criteria according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR (8)). According to the DSM-IV-TR (8, page 197) substance abuse is characterised by ‘a maladaptive pattern of substance use manifested by recurrent and significant adverse consequences related to the repeated use of substances’. Substance dependence is a more advanced state of drug abuse, the essential feature of which is ‘a cluster of cognitive, behavioural and physiological symptoms indicating that the individual continues use of the substance despite significant substance-related problems. There is a pattern of repeated self-administration that can result in tolerance, withdrawal, and compulsive drug-taking behaviour’ (8, page 199). Withdrawal symptoms do not have to be met for a cannabis dependence diagnosis (8), though this has been subject to debate (43).
