BACKGROUND: Few studies have assessed how children are affected by parental alcohol consumption without clinically diagnosed alcohol problems, especially in relation to more long-term and severe consequences. The aim is to investigate how fathers' alcohol use is related to the risk for substance-related disorders in offspring.

METHOD: A prospective cohort study of 64 710 Swedish citizens whose fathers were conscripted for compulsory military training at ages 18-20 in 1969/70. Information on fathers' alcohol consumption, frequency of intoxication and apprehended for drunkenness, was collected during conscription. Offspring was followed for substance-related disorders from age 12 to end of follow up in 2009.

RESULTS: All measures of fathers' alcohol use were significantly and positively associated with risk for substance-related disorders in offspring. The associations were to a large extent explained by other risk factors in childhood. In the fully adjusted model, those with fathers in the highest alcohol consumption quintile still had a 63% higher risk (HR=1.63 CI 1.26-2.12) of substance-related disorders compared to those whose fathers' reported abstinence. The highest risk was found among offspring to fathers with alcohol-related disorders or that had been apprehended for drunkenness, with a more than two-fold increased risk for substance-related disorders.

CONCLUSIONS: Despite the lower risk found among offspring to fathers with sub-clinical drinking when compared to those with alcohol-related disorders, the former group accounts for a much larger proportion of all cases of substance-related disorders in the population, prompting universal prevention efforts targeting the level of total alcohol consumption in society.