Several studies have investigated the relationship between psychiatric comorbidity and ADHD in adults. However, there are conflicting results regarding gender differences in such comorbidities in adults with ADHD. This study aimed to determine whether there is a gender-modified association between psychiatric comorbidities and ADHD in adults, and if so, the proportion of psychiatric disorders among men and women that could be attributed to a comorbid diagnosis of ADHD.
This was a cross-sectional analysis conducted in a cohort of Norwegian adults (N=1,701,206) identified by linking four Norwegian national registries, who were born between 1967 and 1997 and were alive and living in Norway at record linkage in 2015*. The following comorbid psychiatric disorders were included in the analysis: anxiety; bipolar disorder; depression; personality disorder; schizophrenia; and substance-use disorder. Absolute prevalence differences of psychiatric disorders between adults with and without ADHD were calculated using predicted prevalences from a Poisson regression model, which was adjusted for birth year (5-year periods). The relative excess risk due to interaction was used to evaluate the significance of interactions by gender on the additive scale.
In this study, 2.4% of the population (n=40,103; mean age=31.0 years; 44.4% female) were identified as having adult ADHD† in 2015. The prevalence of comorbid psychiatric disorders was higher in adults with ADHD: 53.5% of women and 48.5% of men with ADHD had ≥1 psychiatric comorbidity, compared with 13.7% and 9.1% of women and men without ADHD, respectively. Adult ADHD was most closely associated with bipolar disorder, personality disorders and substance-use disorder. The prevalences of comorbid psychiatric disorders for men and women with ADHD, respectively, were as follows: anxiety (14.8% vs 28.7%); bipolar disorder (8.9% vs 13.5%); depression (17.1% vs 31.9%); personality disorder (8.7% vs 14.0%); schizophrenia (4.1% vs 2.7%); and substance-use disorder (26.6% vs 15.8%). Differences in prevalence between ADHD and non-ADHD adults were significantly larger in women than in men for all psychiatric disorders except schizophrenia and SUD.
Although this study showed that there is a gender-modified prevalence of psychiatric comorbidities in adults with ADHD, there are some study limitations. Since this was a cross-sectional study based on data registered over different time periods up to 2015, this limits the study of temporal relations. In addition, adults with ADHD registered before 2004 and those not receiving ADHD medication because of contraindications or other causes before 2008 were not included in the study. Further, information on psychiatric comorbid disorders was based on diagnoses registered in secondary healthcare, missing comorbidities registered in primary care.
Nevertheless, results from this study are informative from both a clinical and public health perspective, and highlight which subgroups of patients with ADHD may need to be prioritised to prevent and treat comorbidities. In addition, it may be of particular importance for clinicians to be aware of possible underlying ADHD when adults present with symptoms of psychiatric disorders.
Read more about gender-modified psychiatric comorbidities in adult ADHD here
*Record linkage was established using the national identification number unique to each Norwegian resident
†Adults with ADHD were defined as those registered has having ADHD at age ≥18 years during 2008–2015, and those who had been dispensed their last prescription of ADHD medication at age ≥18 years during 2004–2015
Solberg BS, Halmøy A, Engeland A, et al. Gender differences in psychiatric comorbidity: a population-based study of 40,000 adults with attention deficit hyperactivity disorder. Acta Psychiatr Scand 2018; 137: 176-186.