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The risk for obesity and depression co-occurring with attention-deficit/hyperactivity disorder (ADHD) is increased in adolescents and adults with ADHD. Moreover, ADHD in adolescence predicts obesity and depression in later life. Sleep disorders such as a not being able to fall asleep, shorter sleep and a shifted day-night cycle (circadian rhythm) are also common among individuals with ADHD. In turn, sleep problems have been linked to obesity.
In a series of papers, a research group from the Netherlands tried to make sense of these findings, suggesting a connection between ADHD symptoms, depression, sleep disturbances and weight. The first study1 investigated the associations between ADHD, sleep problems and depression by obtaining self-reported sleep/wake characteristics, lifestyle factors and information on physical and mental health from 202 adults with ADHD and 189 control participants. The second study2 extended the first by adding a group of 114 adults with obesity to examine whether sleep problems and unstable eating patterns (circadian rhythm disruptions) may be the mechanism linking ADHD to obesity.
Individuals with ADHD reported problems sleeping, including shorter sleep and difficulties falling asleep. Shorter and later sleep was further associated with hyperactivity symptoms and depression, as well as with higher Body Mass Index (BMI). The authors, therefore, propose common origin for the sleeping problems and ADHD symptoms, which may lead to depressive symptoms. Moreover, both sleep duration and unstable eating patterns mediated the association between ADHD symptoms and BMI. This means that higher ADHD symptoms increased the risk for worse sleep and unstable eating patterns, leading to an increased risk for a higher BMI. These results support the idea that circadian rhythm disruption is a mechanism linking ADHD symptoms to obesity.
While these are interesting and important findings, the studies also suffered a few methodological shortcomings. Firstly, cross-sectional studies like these do not allow strong conclusions about cause and effect. Secondly, the data are based on self-report measures, which have not been extensively validated. Thirdly, due to the high proportion of young, better-educated females and the high levels of depressive symptoms in the control group, the sample may not be representative of the general population. Lastly, confounding diagnoses such as mood, anxiety and substance use disorders, were not assessed comprehensively, despite findings from the initial analysis suggesting a relationship between ADHD, sleep problems and depression.
These thought-provoking initial results, therefore, require replication using a longitudinal design, as well as more validated and objective measures, in representative samples. The European collaborative study CoCA (Comorbid conditions of ADHD) aims to investigate major comorbid conditions in ADHD, including depression and obesity, using diagnostic interviews and physical examinations. In addition, CoCA will examine sleep and physical activity in adolescents and adults with ADHD using objective light sensors and accelerometers. To establish whether therapies combining ADHD treatment and treatment of the circadian rhythm disruptions are effective in treating and preventing obesity and depression in patients with ADHD, CoCA will test two potential interventions, namely bright light therapy and exercise, in a 10-week trial. While bright light therapy is proposed to have an effect on the circadian rhythm and is an established therapy for major depression in adolescents and adults, exercise prevents and reduces obesity in adolescents and adults, and may also improves depressive symptoms.
- Bijlenga, D. et al. Associations Between Sleep Characteristics, Seasonal Depressive Symptoms, Lifestyle, and ADHD Symptoms in Adults. J. Atten. Disord. 17, 261–275 (2013).
- Vogel, S. W. N. et al. Circadian rhythm disruption as a link between Attention-Deficit/Hyperactivity Disorder and obesity? J. Psychosom. Res. 79, 443–450 (2015).