Prior research indicates that parental psychiatric disorders increase their offspring's risk of substance use problems. Though the association is likely bidirectional, the effects of an adult child's substance use on parental mental health remain understudied. We examined parents' psychotropic medication use trajectories by parental sex and educational attainment before and after a child's alcohol- or narcotics-attributable hospitalization. We identified Finnish residents, born 1979-1988, with a first hospitalization for substance use during emerging adulthood (ages 18-29, n = 12,851). Their biological mothers (n = 12,283) and/or fathers (n = 10,765) were followed for the two years before and after the hospitalization. Psychotropic medication use was measured in three-month periods centered around the time of child's hospitalization, and the probability of psychotropic medication use at each time point was assessed using generalized estimating equations logit models. Among mothers, the prevalence of psychotropic medication use increased during the year before, peaked during the 0-3 months after hospitalization, and remained at a similarly elevated level until the end of follow-up. The prevalence among fathers increased gradually and linearly across follow-up, with minimal changes evident either directly before or after the hospitalization. Parents' educational attainment did not modify these trajectories. Our results highlight the importance of considering linked lives when quantifying substance use-attributable harms and underscore the need for future research examining the intergenerational spillover effects of substance use in both directions, particularly in mother-child dyads.