ebbadurietz

Physical exercise and the brain

Emerging evidence from research studies suggests that physical activity can improve attention, brain function and well-being. In an attempt to understand more about the beneficial effects of high-intensity exercise, we recently conducted a study on the effect of PHysical Activity on Brain function (PHAB study). We examined whether cycling at a high intensity for 20 minutes would improve brain-activity (electroencephalography; EEG) measures of attention and focus during computerised tasks. We also aimed to investigate whether some individuals, for example those who are physically fit, would benefit more or less from exercise.

Does high-intensity exercise improve attention?

Participants (young adult men) were invited to our research centre, where they completed computer tasks while we recorded their brain activity. In the first task, they were asked to respond to letter ‘X’ following an ‘O’, but not to respond if another letter was presented after an ‘O’. Participants performed the task both before and after exercise and rest, and so we were able to test if their brain activity changed after exercise.

We found that an attention measure called the “P3” was enhanced after exercise but not after rest. This suggests that the intense exercise session led to improvements in their attention. These improvements in attention from exercise were equal across participants, regardless of how physically fit they were.

The participants also performed two subsequent computer tasks, but we did not find improvements after exercise in these tasks. We believe that the beneficial effects of exercise may have worn off by the time that they performed these tasks.

These results suggest that intense exercise may improve attention. Exercise may therefore be beneficial for individuals with impairing levels of inattentive and restless behaviours, such as ADHD. This is currently being tested in the clinical trial CoCA (https://mind-the-gap.live/2018/10/09/10-weeks-of-physical-exercise-or-light-therapy/) (https://mind-the-gap.live/2017/02/18/coca-proud-trial-ready-to-roll/).

ADHD is a heritable disorder, which means that genes contribute to the risk for getting the disorder. There are hundreds or even thousands of genes that contribute to ADHD, and while each single gene itself will not cause ADHD, together they contribute to the risk. But it is important to note that genes are not everything – environmental influences, such as preterm birth or exposures during pregnancy, may also contribute to the risk for ADHD.

Individuals with ADHD sometimes have other co-occurring conditions, such as mood disorders, obesity and substance abuse. This has led to the important research question of why do these conditions often co-occur with ADHD. Are there shared risk factors?

Comorbidity

We know that people with ADHD not only tend to have a family history of ADHD, but they also are more likely to have siblings or parents with certain other co-occurring traits and disorders. This suggests that there are overlapping familial risk factors – which could be genes – between ADHD and other conditions.

A very large and recent genetic study that examined thousands of common genetic markers across our DNA, identified for the first time several genes that underlie risk for ADHD². This information allowed us to investigate the genetic overlap between ADHD and other disorders using actual genetic data. In our new paper published in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging³, we selected a bunch of genetic markers that most strongly underlie risk for ADHD, identified in the previous genetic study, and tested if they showed an overlap with other traits and disorders that often co-occur with ADHD. We tested this on a very large sample of 135,000 people in the UK. We found that some of the genetic risk factors were shared between ADHD and co-occurring conditions in the general population, specifically – atypical cognitive functioning, higher body mass index, neurotic behaviour, anxiety, depression, risk-taking behaviour, smoking and alcohol use.

Our study findings suggest that genes do, at least to some extent, explain the overlap between ADHD and co-occurring conditions. These genetic factors contribute to cognitive functioning, body mass index, mood symptoms and substance use in the general population.

The aim of this research is to further our understanding of ADHD and co-occurring traits and disorders. A better understanding of why ADHD often co-occurs with other conditions may help in the development of new treatments. Also, if we know how to predict which individuals with ADHD are at risk for other co-occurring disorders, we will be in a better position to offer early interventions that could prevent such further problems from developing.

Ebba Du Rietz and Jonna Kuntsi

References:

Faraone SV, Perlis RH, Doyle AE, Smoller JW, Goralnick JJ, Holmgren MA, Sklar P. Molecular genetics of attention-deficit/hyperactivity disorder. Biol Psychiatry. 2005; 57:1313–1323. doi: 10.1016/j.biopsych.2004.11.024.
Demontis D, Walters RK, Martin J, et al. Discovery of the first genome-wide significant risk loci for ADHD. bioRxiv 145581. 2017. doi: https://doi.org/10.1101/145581.
Du Rietz E, Coleman J, Glanville K, Wan Choi S, O’Reilly PF, Kuntsi J. Association of polygenic risk for attention-deficit/hyperactivity disorder with co-occurring traits and disorders. Biol Psychiatry: CNNI. In press. doi: https://doi.org/10.1016/j.bpsc.2017.11.013