Nutrition and ADHD

 There is a well-documented relationship between dietary factors, health and human behavior. Severe malnutrition produces neurological and psychiatric symptoms. It is also assumed that dietary factors play a role in common mental disorders, such as ADHD, but this is less established and more difficult to investigate. A few studies have documented a beneficial effect of dietary interventions and vitamin supplements in ADHD in children and adults.

To examine the nutritional status in ADHD, Landaas et al. recently compared blood vitamin levels in 133 adult ADHD patients and 131 healthy controls. In the ADHD group there was a clear overrepresentation in the group with low levels of vitamins B2, B6 and B9.

It is yet unclear whether these vitamin levels are associated with ADHD symptoms, or whether they are the result of altered dietary intake or metabolism in ADHD patients. However, it is possible that the differences reflect dietary habits that are different in a subgroup of ADHD patients and controls. Dietary habits are established early during life and may last into adulthood. It is possible that suboptimal dietary habits may precipitate, exacerbate or maintain symptoms of ADHD. More research in larger samples is obviously needed to clarify these issues.


What’s known about comorbid conditions in ADHD?

The European collaborative study CoCA (Comorbid conditions of ADHD) aims to identify and treat major comorbid conditions in ADHD. It is mainly focused on mood and anxiety disorders, substance use and obesity.

However, in addition to these well documented co-occurring problems , other conditions have also been reported to be associated with ADHD. For clinicians and researchers alike, it’s important to be aware of such connections.

In a recent systematic review, Instanes and coworkers attempted to identify and evaluate the scientific evidence published during the past 20 years, connecting adult ADHD with any somatic condition.

Starting from >4000 articles, the authors identified 126 studies that were subjected to further scrutiny. Although many potentially important comorbid conditions were reported, the authors concluded that most of the studies were “small and of modest quality”.

Importantly, many studies suffered from methodological shortcomings, such as using “convenience samples”, where ADHD cases and controls were not adequately matched. Other studies used non-standard diagnostic criteria or protocols, making it difficult to compare date across sites.

Given the importance of this problem, more data is obviously needed. More care should also be given to the design of such studies. In particular, Instanes et al. recommend the use of population based registry studies and common diagnostic protocols to estimate the rates of comorbidity.

CoCA aims to make a major contribution to our understanding of ADHD comorbidities, not only by generating more data, but also by providing more reliable and clinically relevant information.


Instanes JT, Klungsøyr K, Halmøy A, Fasmer OB, Haavik J. Adult ADHD and Comorbid Somatic Disease: A Systematic Literature Review. J Atten Disord. 2016 Sep 22. pii: 1087054716669589. PMID: 27664125

How can we make sense of comorbidity?

Comorbidity, defined as the simultaneous occurrence of more than one disorder in a single patient, is commonplace in psychiatry and somatic medicine. In research, as well as in routine clinical settings.

In March 2016 the new H2020 collaborative project “CoCA” (Comorbidity in adult ADHD) was officially launched, with a 3-day kick-off meeting in Frankfurt, Germany. This ambitious project, which is coordinated by professor Andreas Reif and is co-maintaining this shared blog, will investigate multiple aspects of comorbidity in ADHD.

For instance, CoCA will “identify and validate mechanisms common to the most frequent psychiatric conditions, specifically ADHD, mood and anxiety disorders, and substance use disorders (SUD), as well as a highly prevalent somatic disorder, i.e. obesity”.

As reflected in this bold mission, most scientists trained in the biological sciences agree that studies of overlapping and concurrent phenomena may reveal some underlying common mechanisms, e.g. shared genetic or environmental risk factors.

However, particularly in psychiatry and psychology, the origins of comorbidity have been fiercely debated. Critics have argued that observed comorbidities are “artefacts” of the current diagnostic systems (Maj, Br J Psychiatry, 2005 186: 182–184).

This discussion relates to fundamental questions of how much of our scientific knowledge reflects an independent reality, or is merely a product of our own epistemological traditions. In psychiatry, the DSM and ICD classification systems have been accused of actively producing psychiatric phenomena, including artificial diagnoses and high comorbidity rates, rather than being “true” representations of underlying phenomena.  Thus, the “constructivist” tradition argues that diagnostic systems are projected onto the phenomena of psychiatry, while “realists” acknowledge the presence of an independent reality of psychiatric disorders.

In an attempt to explain these concepts and their implications, psychiatric diagnoses and terminology have been termed “systems of convenience”, rather than phenomena that can be shown to be true or false per se (van Loo and Romeijn, Theor Med Bioeth. 2015, 41-60). It remains to be seen whether such philosophical clarifications will advance the ongoing debate related to the nature of medical diagnoses and their co-occurrence.

CoCA will not resolve these controversies. Neither can we expect that our new data will convince proponents of such opposing perspectives.

It is important to acknowledge the imperfections and limitations of concepts and instruments used in (psychiatric) research.

However, it may provide some comfort that similar fundamental discussions have a long tradition in other scientific disciplines, such as physics and mathematics. Rather  than being portrayed as a weakness or peculiarity of psychiatric research, I consider that an active debate, with questioning and criticism is considered an essential part of a healthy scientific culture.

Hereby, you are invited to join this debate on this blog page!Wooden ruler vector