Mental disorders and having a first child among young adults in Finland

Background: Fertility rates have declined during the 2010s in many high-income countries, with a strong decrease in Finland. Mental disorders might contribute to this decline, given that they became a major cause of work disability in Finland. We examined associations between broad and specific categories of mental disorders and the likelihood of having a first child among young people, and the role of partnership status in these associations. Methods: We conducted a nationwide register-based cohort study including all men and women born in 1980-1995 in Finland (n = 1,210,662). Exposures were mental disorders with ICD-10 subchapter F-diagnosis, and outcome was time to first childbirth. Results: The diagnosis of almost any mental disorder was associated with a lower likelihood of having a first child among men and women, with schizophrenia and intellectual disabilities having the strongest associations. People with substance use, childhood onset, anxiety, or any mental disorders had a higher rate of having a first child by age 25 than people without these diagnoses; by age 30-35 these associations became negative. People with mental disorders were also less likely to cohabit. Among those who never cohabited, women with substance use disorders or childhood onset disorders were more likely to have a first child compared to women without these disorders. Conclusions: Almost all mental disorders were associated with a lower rate of having a first child, especially among men. These findings imply that well-functioning mental health services are important also from a fertility perspective, which should be considered by policy makers.