Intelligence across childhood in relation to illegal drug use in adulthood: 1970 British Cohort Study

Centre for the Development and Evaluation of Complex Interventions for Public Health Improvement, Cardiff University, 7th Floor Neuadd Meirionnydd, Heath Park, Cardiff CF14 4YS, UK.
Journal of epidemiology and community health (Impact Factor: 3.5). 11/2011; 66(9):767-74. DOI: 10.1136/jech-2011-200252
Source: PubMed


Recent reports have linked high childhood IQ scores with excess alcohol intake and alcohol dependency in adult life, but the relationship with illegal drug use in later life is relatively unknown.
The authors used data from a large population-based birth cohort (1970 British Cohort Study) with measures of lifetime cannabis and cocaine use, parental social class and psychological distress at 16 years; cannabis, cocaine, amphetamine, ecstasy and polydrug use (more than three drugs) in the past 12 months; and social class, educational attainment and gross monthly income at 30 years. All members of the cohort with IQ scores at 5 or 10 years were eligible to be included in the analyses.
Of the 11603 (at 5 years) and 11397 (at 10 years) cohort members eligible, 7904 (68.1%) and 7946 (69.7%) were included in the analyses. IQ scores at 5 years were positively associated with cannabis (OR ((bottom vs top tertile)) =2.25, 95% CI 1.71 to 2.97) and cocaine use (OR 2.35, 95% CI 1.41 to 3.92) in women and with amphetamines (OR 1.46, 95% CI 1.03 to 2.06), ecstasy (OR 1.65, 95% CI 1.15 to 2.36) and polydrug use (OR 1.57, 95% CI 1.09 to 2.26) in men at 30 years. IQ scores at 10 years were positively associated with cannabis, cocaine (only at 30 years), ecstasy, amphetamine and polydrug use. Associations were stronger in women than in men and were independent from psychological distress in adolescence and life-course socioeconomic position.
High childhood IQ may increase the risk of illegal drug use in adolescence and adulthood.

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    • "For example, heightened use is undoubtedly associated with increased access to money to buy recreational goods. Indeed, higher adolescent cognition has emerged as a robust predictor of elevated cocaine use (Kanazawa and Hellberg 2010; White and Batty 2012), even as protective educational gradients have emerged (Miech 2008). However, health behaviors can also signal social status hierarchies (Cockerham 2005). "
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    • "Indeed, executive abilities are necessary to find, acquire, and sustain illegal drug use (Joyal et al., 2003), so FEP C + would be composed of patients with relatively better premorbid cognitive functions and premorbid social adjustment (Rodríguez-Sánchez et al., 2010) who had early contact with Cannabis, followed by a psychotic disorder emerging in a more structurally preserved brain. This is consistent with recent data showing an association between high premorbid IQ and Cannabis use (White and Batty, 2012). A recent study also reported less severe cognitive impairments and GM deficits in the PFC in patients with schizophrenia and Cannabis use (Schnell et al., 2012), although that study was different in terms of methodological issues (e.g., lack of a healthy control group and limited number of inspected brain regions). "
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    • "These results add to the limited evidence which suggests that greater IQ in childhood might be linked with greater use of illegal drugs in adulthood [22e24]. Of particular relevance is our replication of stronger associations between IQ and drug use in women than men [22], a finding which has been found to also apply to the relationship between childhood IQ and excess alcohol consumption and alcohol dependency in adulthood [4] [6]. This study has several strengths, including its large sample size and detailed data on the participants' early life that allowed us to adjust for a range of potentially mediating and confounding factors. "
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