The relative age effect on antidepressant use in children and adults

Having young relative age in school is an identified risk factor for depression among schoolchildren, but it is unclear if this risk remains in adulthood. This study aimed to investigate the association between young relative age in school and antidepressant use across different age groups.

This population-based study used data from the Swedish Medical Birth Register and the Prescribed Drug Register combined with data from Statistics Sweden. The population of 3,575,510 subjects, (48.6 % female), was split into different age groups, with groups spanning from 0 to 7 years of age to 40-45 years of age. The odds ratios (OR) of antidepressant use in the first as compared to the fourth birth-quarters, was determined by logistic regression.

Young relative age was positively associated with use of antidepressants with an OR of 1.05 (95 % confidence interval, 1.05-1.06) in the study population. This association was significant in all age groups that had started school and remained among adults.

Data on indication for antidepressant medication prescription was unavailable, some subjects might have had antidepressants for other disorders then anxiety and depression. Another limitation is that it is unclear when during schooling children were accelerated/deferred. Moreover, antidepressant medication is uncommon among small children.

This study shows that young relative age within the school year increases the prevalence of antidepressant use in all investigated age-groups that had started school, long after the end of schooling.