ADHD and chronic pain

Recognition that ADHD (attention deficit hyperactivity disorder) is associated with chronic pain has increased in recent years. ADHD is generally diagnosed in children, with boys more commonly affected than girls. Chronic pain is usually an adult problem and mostly in women. At first glance, the main clinical features of ADHD (hyperactivity, inattention, impulsivity) do not have much in common with the clinical features of chronic pain (pain, inactivity, chronic fatigue, sleep problems). Mood disorders such as depression and anxiety often develop as a result of the long-term fatigue due to ADHD or chronic pain and complicate the psychological problems, including substance abuse or impaired cognition. Up to 80% of adults with ADHD have some form of comorbid mental health problems.

It should be kept in mind that current diagnostic criteria are useful for diagnosing children and adolescents and are not fully applicable to the adult population. Adult adhd may present differently. Hyperactivity plays a lesser role and fatigue more strongly defines the clinical picture of ADHD in adults.

In clinical practice, ADHD and pain conditions are rarely recognized and treated simultaneously. Treatment of ADHD and pain usually occurs in separate clinical settings. A better understanding of the potentially common underlying neurobiological underpinnings related to pain processing, cognition, and affect regulation would allow for better treatment strategies to be developed in patient-centered rather than specialized/disease-centered healthcare settings.

How can ADHD be identified in adult patients with chronic pain?

ADHD symptoms may not be typical because hyperactivity is not the main feature of the disorder. Hyperactivity may be episodic and alternate with increased pain and concurrent hypoactivity and may be confused with bipolar disorder. Symptoms such as hyperactivity appear to diminish from childhood to adulthood and the clinical presentation is more toward attention deficit disorder. Impaired cognition or attention problems persist or even worsen with age. It may be that so-called "fibro fog" or "brain fog" has something to do with this deterioration.

A person who has been previously diagnosed with attention deficit hyperactivity disorder

A person with a pain problem who has been previously diagnosed (usually in childhood or adolescence) with ADHD may develop problems related to taking ADHD medications (e.g., headaches, painful cramping, anxiety), which shapes the overall clinical picture of a chronic pain disorder. ADHD medications intended among other to relieve physical pain are usually stimulants and may later interact with pain medications intended to calm the nervous system.

Behavioral problems in the form of motor hyperactivity may predispose adhd patients to musculoskeletal overuse. Musculoskeletal pain that blocks motor hyperactivity, even if initially a nociceptive phenomenon (pain directly related to healing of damaged structures), may increase anxiety even more in adhd patients than in people without adhd. High health-related anxiety in the acute state of an injury is a risk factor for the development of chronic pain. It may be that recognition of chronic pain developement in adhd patients is delayed, because of the hyperfocus on structural damage and not on problems with behavioral adaptation to changes in the body in the acute state of injury or overuse.

When a patient with both adhd and pain is acutely treated with pain medications (e.g., opioids, gabapentinoids, benzodiazepines, muscle relaxants) for an injury or acute exacerbation of nonspecific pain, much more caution should be exercised and careful consideration should be given regarding potential substance use disorder.

Is there a common neurobiological background for ADHD and chronic pain?

ADHD has been documented more frequently in children, adolescents, and also adults with chronic pain, and there is preliminary evidence for a mechanistic interplay between pain perception and characteristic manifestations of ADHD (impulsivity and attention deficits). There is a link between attentional deficits and alterations in sensory processing that is definitely associated with pain signaling. There is some evidence of an association between ADHD in childhood and the risk of developing chronic pain later in life. However, because there appears to be a diagnostic bias that results in boys being diagnosed with ADHD more often than girls, and there is also evidence of neurobiological gender differences between male and female ADHD, we need much more research to better understand the relationship between chronic pain and ADHD traits.

Attention deficit hyperactivity disorder is a form of reward deficiency syndrome related to dopamine signaling and disruption of reward behavior. Alteration of dopamine signaling is associated with attention and motivation problems and decreased learning ability, which increases the risk of substance use disorder, a major problem in patients with chronic pain disorders.

Regarding executive functions and motivation, patients with attention-deficit/hyperactivity disorder generally show a characteristic behavioral pattern of preferring small, immediate reinforcements to large, delayed ones. There is some neurobiological basis behind this so-called delayed gratification phenomenon - a delay in immediate anticipatory dopamine signaling in ADHD patients compared to patients without ADHD. On the other hand, ADHD patients show hyperfocus on certain activities that particularly interest them, while having difficulty with boring tasks.

Sugar is associated with attention problems and pain outbursts.

If you have uncontrollable, persistent pain (in multiple places), sugar cravings, and problems with brain fog, you may be struggling with both ADHD and chronic pain. Does sugar consumption promote ADHD or is it the other way around? We do not know yet; it's like the chicken and the egg. Sugar definitely promotes inflammatory pain and exacerbates fibromyalgia syndrome in all aspects (pain, fatigue, fibrofog, sleep problems). There is evidence that people with central pain (as in the case of fibromyalgia) have insulin resistance to some degree, which may be related to excessive consumption of high glycemic index foods, such as processed sugar. Unstable blood sugar levels may be the trigger for headaches. Wearing a device to continuously monitor blood glucose levels would help clarify this issue.

There is evidence that consumption of high amounts of fructose (e.g., processed sugar, corn syrup, etc.) may result in lower bioavailability of triptophan in people with lower potency of GLUT5 (fructose transporter through the intestinal mucosa in the duodenum), which may be related to certain central pain mechanisms, although different from those related to dopamine signaling. Fructose malabsorption leads to fructose accumulation in the colon and is associated with zinc deficiency, which has been shown to be related to autism spectrum disorder, another disorder that may be related to the widespread pain syndrome. Can someone be on the spectrum (of autism) and have ADHD and chronic pain? Yes, it is possible and has been observed in children up to 17 years of age. I am not aware of any scientific data showing comorbidity of chronic pain, autism trait and attention deficit disorder comorbidity among adult population. Pain medicine community might not be aware enough of the importance of clinical recognition of such comorbidities. Growing old undiagnosed with such complex health problems can be very stressful and later present more like chronic fatigue syndrome/fibromyalgia or major depressive disorder.

And this leads us to another neurodevelopmental disorder, Autism Spectrum Disorder, which deserves special attention in relation to body pain and will be discussed in one of the following posts.