From early to fewer first births: ADHD and family formation among young adults

Attention-deficit/hyperactivity disorder (ADHD) is common and associated with relationship difficulties, which may influence entry into parenthood.

We used Finnish population register data to follow 759,430 individuals born in 1982-1993 and examined how ADHD is associated with the likelihood and timing of a first birth. ADHD was identified using healthcare diagnoses and prescription records. We estimated discrete-time event history models and sibling fixed-effects models to account for shared family background. All analyses were conducted separately for women and men.

In models adjusted for age and birth cohort, ADHD was associated with a lower likelihood of a first birth (ages 18-38) (men OR 0.92; women OR 0.90). After adjusting for partnership characteristics, the association reversed (men OR 1.07; women OR 1.09). All age-stratified analyses showed that ADHD was associated with a higher likelihood of first birth at ages 18-23, but with a lower likelihood at ages 24-30 and 31-38, indicating earlier entry into parenthood among individuals with ADHD. Results from sibling fixed-effects models were broadly similar to the population-level estimates, suggesting limited confounding by shared family background.

ADHD is associated not only with earlier entry into parenthood but also with a reduced overall probability of having a first child. Accounting for partnership status is important, as it largely explains the negative association observed in age-adjusted models. These findings highlight partnerships as a key pathway linking ADHD to fertility outcomes.