Cognitive ability, alcohol use and alcohol-related harm

Cognitive ability has been shown to be inversely associated with several health outcomes, both somatic and psychiatric. The findings regarding the association between cognitive function and alcohol-related outcomes have however not been consistent. Furthermore, there has been a lack of knowledge regarding possible differences between genders and what mechanisms there would be that could explain the association. Also, information regarding school performance and alcohol-related outcomes has been needed. The overarching aim of this thesis was to further investigate the association between cognitive function, alcohol use and alcohol-related harm.

Three different data bases were used in this thesis, The Swedish Conscript Cohort consisting of 49 321 Swedish males, the Evaluation Through Follow-up data base with a total of 21 809 Swedish men and women and School Register data with a total of 213 395 Swedish men and women.

In study I, using the Swedish Conscript cohort, we investigated the association between IQ-test results from late adolescence and alcohol-related hospital admission and death. An inverse, grade association was found for both outcomes. This was a longitudinal, cohort study.

In study II, using the Swedish Conscript cohort, the association between IQ-test results in late adolescence and alcohol consumption, measured both as total alcohol intake and pattern of drinking. Lower IQ-test results were found to be associated with a higher alcohol consumption, regarding both outcomes.

In study III, using the Evaluation Through Follow-up data base, we found an inverse graded association between IQ-test results measured in childhood and alcohol-related hospital admission and death. There seemed to be no interaction for gender in the association, and socio-economic position as adult was assessed to at least partly mediate in the found association, for both outcomes.

In study IV, using School register data, we found a graded, inverse association between grade point average from 9th grade and alcohol-related admission to hospital, for both men and women. IQ-test result did not seem to be a confounder in the association.

In conclusion, we found that IQ-test results and school grades were inversely associated with alcohol use and alcohol-related harm. The results were similar for men and women, where investigated and socio-economic position as adult, was assessed a possible mediator in the association between intelligence and alcohol-related harm.

List of scientific papers

I. Sjölund, S, Allebeck, P., Hemmingsson, T. (2012). Intelligence quotient (IQ) in adolescence and later risk of alcohol-related hospital admissions and deaths—37-year follow-up of Swedish conscripts. Addiction, 107(1):89-97.
https://doi.org/10.1111/j.1360-0443.2011.03544.x

II. Sjölund, S., Hemmingsson, T., Allebeck, P. (2015). IQ and level of alcohol consumption - Findings from a national survey of Swedish conscripts. Alcoholism: Clinical and Experimental Research, 39(3):548-55.
https://doi.org/10.1111/acer.12656

III. Sjölund, S., Hemmingsson, T., Allebeck, P. (2015). IQ and alcohol-related morbidity and mortality among Swedish men and women – the importance of socio-economic position. [Accepted]
https://doi.org/10.1136/jech-2014-204761

IV. Sjölund, S., Hemmingsson, T., Falkstedt, D., Allebeck, P. School grades and alcohol-related disease. [Manuscript]