Attention-deficit hyperactivity disorder (ADHD) is often comorbid with other medical conditions in adult patients. However, ADHD is extremely underdiagnosed in adults and little is known about the medical comorbidities in undiagnosed adult individuals with high ADHD liability. In this study we investigated associations between ADHD genetic liability and electronic health record (EHR)-based ICD-10 diagnoses across all diagnostic categories, in individuals without ADHD diagnosis history.

We used data from the Estonian Biobank cohort (N = 111 261) and generated polygenic risk scores (PRS) for ADHD (PRSADHD) based on the ADHD genome-wide association study. We performed a phenome-wide association study (PheWAS) to test for associations between standardized PRSADHD and 1515 EHR-based ICD-10 diagnoses in the full and sex-stratified sample. We compared the observed significant ICD-10 associations to associations with (1) ADHD diagnosis and (2) questionnaire-based high ADHD risk analyses.

After Bonferroni correction (p = 3.3 × 10−5) we identified 80 medical conditions associated with PRSADHD. The strongest evidence was seen with chronic obstructive pulmonary disease (OR 1.15, CI 1.11–1.18), obesity (OR 1.13, CI 1.11–1.15), and type 2 diabetes (OR 1.11, CI 1.09–1.14). Sex-stratified analysis generally showed similar associations in males and females. Out of all identified associations, 40% and 78% were also observed using ADHD diagnosis or questionnaire-based ADHD, respectively, as the predictor.

Overall our findings indicate that ADHD genetic liability is associated with an increased risk of a substantial number of medical conditions in undiagnosed individuals. These results highlight the need for timely detection and improved management of ADHD symptoms in adults.

There has been little research on the association of attention-deficit/hyperactivity disorder (ADHD) with co-occurring physical diseases. The aim of this study was to examine the association between possible ADHD and physical multimorbidity (i.e. = 2 physical diseases) among adults in the English general population.

Data were analyzed from 7274 individuals aged = 18 years that came from the Adult Psychiatric Morbidity Survey 2007. ADHD symptoms were assessed with the Adult Self-Report Scale (ASRS) Screener. Information was also obtained on 20 self-reported doctor/other health professional diagnosed physical health conditions present in the past 12 months. Multivariable logistic regression and mediation analyses were conducted to assess the associations.

There was a monotonic relation between the number of physical diseases and possible ADHD (ASRS score = 14). Compared to those with no diseases, individuals with = 5 diseases had over 3 times higher odds for possible ADHD (odds ratio [OR]: 3.30, 95% confidence interval [CI]: 2.48–4.37). This association was observed in all age groups. Stressful life events (% mediated 10.3–24.3%), disordered eating (6.8%), depression (12.8%), and anxiety (24.8%) were significant mediators in the association between possible ADHD and physical multimorbidity.

Adults that screen positive for ADHD are at an increased risk for multimorbidity and several factors are important in this association. As many adults with ADHD remain undiagnosed, the results of this study highlight the importance of detecting adult ADHD as it may confer an increased risk for poorer health outcomes, including physical multimorbidity.

The association between physical disorders and suicide remains unclear. The aim of this study was to examine the relationship between physical disorders and suicide after accounting for the effects of mental disorders.

Individuals who died by suicide (n = 2100) between 1996 and 2009 were matched 3:1 by balancing score to general population controls (n = 6300). Multivariate conditional logistic regression compared the two groups across physician-diagnosed physical disorders [asthma, chronic obstructive pulmonary disease (COPD), ischemic heart disease, hypertension, diabetes, cancer, multiple sclerosis and inflammatory bowel disease], adjusting for mental disorders and co-morbidity. Secondary analyses examined the risk of suicide according to time since first diagnosis of each physical disorder (1–90, 91–364, ⩾ 365 days). Similar analyses also compared individuals with suicide attempts (n = 8641) to matched controls (n = 25 923).

Cancer was associated with increased risk of suicide [adjusted odds ratio (AOR) 1.40, 95% confidence interval (CI) 1.03–1.91, p < 0.05] even after adjusting for all mental disorders. The risk of suicide with cancer was particularly high in the first 90 days after initial diagnosis (AOR 4.10, 95% CI 1.71–9.82, p < 0.01) and decreased to non-significance after 1 year. Women with respiratory diseases had elevated risk of suicide whereas men did not. COPD, hypertension and diabetes were each associated with increased odds of suicide attempts in adjusted models (AORs ranged from 1.20 to 1.73).

People diagnosed with cancer are at increased risk of suicide, especially in the 3 months following initial diagnosis. Increased support and psychiatric involvement should be considered for the first year after cancer diagnosis.