ADHD is a disorder that has numerous comorbids ("comorbids" refer to disorders that often accompany or are seen alongside of ADHD). These include, but are not limited to: Depression, Tourette's, Conduct Disorders, Sleep Disturbances, Restless Legs Syndrome, Body mass and obesity issues, dysgraphia (poor writing skills and abilities), processing disorders, sensory integration disorders as well as several others.
In the midst of all of these co-occurring disorders, there are a few that often evade the attention of both researchers and the general public. One of these is the disorder bulimia nervosa. Bulimia nervosa (which is often simply referred to as bulimia), which is often characterized by eating (and often binging) followed by purging, is a major issue in many industrialized nations, especially among teens and young women. Based on a study by Surman and co-workers, it appears that there is a relatively high correlation and prevalence of bulima and ADHD. A link to a quick synopsis of the study can be found here, but for sake of time, I will summarize a few key findings from the article:
- Impulsive behavior is a hallmark characteristic of ADHD, and impulsivity is also thought to be a major factor in bulimia as well. It is even hypothesized that some type of underlying factor may be responsible for governing both disorders.
- Given the fact that the disorder of bulimia is expressed at much higher frequencies in young females in late adolescence and early adulthood, it is interesting to note that correlations between the two disorders were relatively weak for men and non-adult women. Additionally, this is worth mentioning because the percentage of individuals with ADHD is heavily skewed towards the male side. That being said, the fact that there was not more of a correlation between ADHD and bulimia in males could be a reflection of either a poor sample size or representation of t he general population, or a relatively weak connection between the two disorders (i.e., one this is unable to override the so-called gender bias of bulimia favoring women and ADHD favoring men).
- These results were tallied from 4 relatively large sample pools previously constructed to evaluate the effects of ADHD over an extended, longitudinal, multi-year period of time. This suggests that some of these relatively strong bulimia/ADHD correlations did not appear simply due to random statistical chance.
- Like ADHD, bulimia has been tied to functional imbalances involving several systems of neurotransmitters, which include serotonin and norepinephrine. It is also possible that hormonal surges during puberty may increase imbalances of neurotransmitters like serotonin, especially in females. Since serotonin levels are tied to feelings of satiation or fullness, imbalanced in this key neurotransmitter can interfere with the feedback of normal eating patterns. In addition to social and environmental pressures, this neurotransmitter imbalance may be another contributing factor to the prevalence of bulimia, anorexia and other eating disorders in females of this age.
- Stimulant medications, such as methylphenidate, which are often the first line of treatment for individuals with ADHD, especially those showing pronounced signs of impulsivity and hyperactivity, have shown potential in the treatment of bulimia, albeit through studies with very small sample sizes.
Taking this one step further, it appears that genetics may be an additional overlapping factor involved in stimulant medication treatment for ADHD. For example, some research suggests that different forms of DAT1 may be responsible for the effects of methylphenidate on appetite and eating behaviors including purging (DAT is short for "Dopamine Transporter Gene"). We have seen previously that there is a connection between the DAT gene and ADHD. Located on human chromosome #5, DAT1 has been linked to Parkinson's, Tourette's and substance abuse.Additionally, proteins coded for by the DAT gene are expressed in high concentrations in the basal ganglia region of the brain. The basal ganglia is essentially responsible, among other things, for determining how fast a person's brain "idles" For example, "type A" individuals, who are often workaholics, easily stressed, and always on the go at 100 miles per hour often have overactive basal ganglia, while the more relaxed, easy-going, "type B" personalities typically have less activity in this critical brain region. While there also appears to be a significant overlap between bulimia and depression, individuals with bulimia typically display higher basal ganglia activities than those with isolated depressive symptoms.
Given the prevalent distribution of this gene's expressed proteins in key brain regions like the basal ganglia, and the role of involvement of these brain regions in eating disorders, the DAT gene may be an important determining and regulating factor for bulimia and other eating disorders, especially in the context of comorbid ADHD.
Please note: These final remarks are simply this blogger's opinion on the subject:
I personally find this connection between ADHD and bulimia to be interesting. However, I do believe that we should be cautious when investigating ADHD comorbid disorders. It is tempting sometimes to fall into the trap of falsely assuming that correlation always implies causation, and trying to find underlying causes for disorders and attempting to link ADHD to every other disorder under the sun.
However, the role of the DAT genes, which have been tied to ADHD, do offer at least some credence to at least some degree of genetic predisposition to both ADHD and bulimia. This claim is further strengthened by the degree of overlap involving medication treatments of the two disorders, namely stimulants. However, there have been several documented cases of the disappearance of bulimia symptoms following treatment with methylphenidate (Ritalin, Concerta, Daytrana, etc.) for comorbid ADHD.
As a result, we may be faced with a "chicken and egg" question: "Does bulimia increase the risk of ADHD or does ADHD increase the risk of bulimia?" (or even "Are they both side effects of an even larger underlying cause?"). Another plausible explanation is that ADHD is a culmination of secondary effects involving bulimia and other eating disorders. Constant purging will typically wreak havoc on the digestive system and lead to improper food and nutrient absorption. I have hinted in previous posts that digestive disorders such as celiac disease can often manifest symptoms which closely approximate those of ADHD. Given the mounting evidence connecting ADHD (or other disorders which exhibit closely related symptoms which could potentially lead to a "false" diagnosis of ADHD if one is not careful) to nutrient deficiencies, it is quite possible that ADHD and its symptoms are secondary effects of nutritional deficits caused by eating disorders such as bulimia.