Concerning risk-taking behavior in the sexual domain, two studies have found a younger mean age of first sexual intercourse in young adults with ADHD compared to individuals without ADHD (26, 27). Flory et al. (26) found earlier initiation of sexual relations without sexual intercourse in participants with ADHD. A younger age at first sexual intercourse was also found in a longitudinal study on children with ADHD and healthy controls followed up for at least 13 years (11). Another study found a moderating effect of conduct problems on the association of ADHD and the age of first sexual intercourse, such that youth with high levels of ADHD symptoms and conduct problems reported the youngest age of first intercourse (28). It is important to note that the samples investigated in these studies were composed almost entirely of male participants. In contrast to findings in these studies, no differences of age at first intercourse were found among girls with and without ADHD (29, 30). However, girls with childhood ADHD engaged in oral sex at a significantly younger age and reported nearly twice as many oral sex partners than their non-ADHD peers (30).
A higher number of sexual partners among individuals with ADHD was found in several studies (11, 26). Young adults with ADHD also engaged in higher rates of other risky sexual behaviors compared with peers without ADHD, such as unprotected sex and sex while intoxicated (31–34). Accordingly, in samples of young adults with ADHD, more sexually transmitted diseases (11, 35), more partner pregnancies, and teenage parenthoods have been registered (27, 36). For example, in a cohort study based on nationwide data from Danish registers, an increased rate of teenage parenthood in individuals with ADHD compared to those without ADHD was found (37). In contrast, individuals with ADHD 25 years or older were significantly less likely to become parents than their non-ADHD counterparts (37), suggesting that there is a great need for evidence-based programs addressing teenage pregnancies in ADHD (37).