Anxiety

Anxiety is the most common co-occurring health condition with Adult ADHD. Individuals diagnosed with ADHD and anxiety disorders have more severe anxiety symptoms than those without ADHD (Katzman et al, 2017)^[1]. We can all be affected by situational anxiety from the stresses of daily life: meeting deadlines, managing relationships, and balancing work and home life. But for those with ADHD, they are facing all the same stresses while battling time blindness, consistent inconsistency^[2], poor memory, and exaggerated emotions. It’s not purely psychological either: the coexistence of ADHD and anxiety is described by biological models as well. Studies have also shown that anxiety in ADHD may make working memory worse, adding to the load individuals with ADHD are already carrying (Gnanavel et al, 2019)^[3].

Fatigue

As well as anxiety, fatigue is another condition associated with ADHD, although it's not currently part of the diagnostic criteria. By consulting data from outpatient services, a 2017 study concluded, “Adults with ADHD experience greater fatigue than healthy controls. Adults with CFS and ADHD share many trans-diagnostic clinical characteristics, including difficulties with low mood, anxiety, and reduced self-efficacy, which impact upon their overall functioning” (Rogers et al, 2017)^[4].

Adults with ADHD often have sensory sensitivities, may have trouble sleeping, and will have times of hyperfocus, all of which contribute to fatigue. However, fatigue in ADHD is not just a result of brain 'overload', but also has a physiological basis, and may in turn worsen the effects of ADHD. A recent study found that the degree of central fatigue and associated changes in tryptophan (a brain chemical) may intensify the severity of symptoms in ADHD - although more studies in adults are needed to confirm this (Yamamoto, 2022)^[5]. We know there's a link between the fatigue signal in people who have chronic fatigue and tryptophan levels in the brain (Castell et al, 1999)^[6]. Other studies have shown that adults with ADHD have lower levels of tryptophan (and its metabolites) than neurotypical individuals, suggesting that these are connected with the severity of current ADHD symptoms (Aarsland et al, 2015)^[7].

Diabetes

As well as anxiety and fatigue, there are other physical conditions affecting adults with ADHD. One of these is diabetes. Studies have shown a potential association between ADHD and altered blood-glucose levels, as well as higher blood glucose readings in type 1 diabetic teenagers with ADHD (Lindblad et al, 2015; Zare Dehnavi et al, 2024)^[8]. Research in Sweden looked at adults with diabetes mellitus in the 50-64 age bracket, and found prevalance of type 2 diabetes was 70% greater among adults with ADHD (Chen et al, 2018).^[9]

Obesity

In genetic studies, obesity, overweight, body fat, and BMI were all correlated with ADHD. Some proposed this was as a result of the impulsivity in ADHD and the effect of that on eating habits. However, genetic correlation data indicates that this propensity for obesity in ADHD goes further: that there there are shared genetic risk factors for obesity and ADHD, and underlying pathophysiology to account for this (Faraone & Larsson, 2019).^[10] While we are still investigating all the factors from 20 or so years of research that associate obesity/overweight and ADHD - and I love that a recent narrative review was entitled, “The Association between ADHD and Obesity: Intriguing, Progressively More Investigated, but Still Puzzling” - there are some possible explanations: genetic factors, abnormal eating pattern and executive function, sedentary lifestyle, disrupted sleep patterns, inflammatory mechanisms (Cortese 2019). Therefore, any dietary plan to support individuals with ADHD would need to account for the potential difficulties that may arise from the barriers ADHD symptoms cause to weight loss or maintenance of healthy weight, and the potentially cyclical nature of ADHD symptoms and weight gain.

Allergies & asthma

In several large-scale studies, they've found evidence of an association with eczema, asthma, and allergic rhinitis (when you have a runny nose all year round) and ADHD. People in these studies with allergies and asthma, were found to be 33-50% more likely to have ADHD. We don't have all the details as to why this is, but there's clearly some link there (Cortese et al, 2018; Liu et al, 2019; van der Schans et al, 2017)^[11]

Autoimmune disorders

Research in Taiwan with 8000 adults diagnosed with ADHD and 32000 controls, found that ADHD patients had ADHD patients had a significantly greater prevalence of ankylosing spondylitis, ulcerative colitis, and autoimmune thyroid disease than the controls, although there were no significant associations with other autoimmune diseases (Chen et al, 2017).^[12]

Epilepsy

As well as studies in Taiwan and Denmark showing that ADHD has an association with epilepsy, a countrywide registry study in Sweden revealed that those with epilepsy were more than 3.5 times likely to have ADHD (Brikell et al, 2018)^[13].

Heart conditions (from medication)

As well as conditions that often co-occur with ADHD, it's also worth here mentioning other potential conditions that result from ADHD medication. For example, recent findings suggest that long-term use of ADHD medication is associated with an increase in cardiovascular risk, especially hypertension and arterial disease (Zhang et al, 2024).^[14] Medication is a personal decision - but it's worth getting all the information and weighing benefits against long-term risks.