In a previous post, we examined whether lead exposure was responsible for worsening ADHD symptoms. We saw that there is a solid (although still somewhat hypothetical) connection between lead and hyperactive behavior. This lead to the blog's conclusion that high lead levels (the exact amount is still hotly debated, but a federal recommendations appear to be headed to a cutoff of around 10 micrograms lead/deciliter of blood. This converts roughly to half of a gramof leadtotal in the entire blood supply in the average adult male, or less than half a gram of lead total in a child's blood ). This post can be found here.
Now it appears that another metal may be connected to hyperactivity. While the connection between manganese and hyperactivity appears to be more strained that that between lead and hyperactivity, it is at least worth mentioning. Additionally, manganese seems to be less tied to actual ADHD behavior (including inattention and impulse control problems alongside hyperactivity), and more towards generalized hyperactivity. Nevertheless, like the post on lead and hyperactivity mentioned previously, there at least remains that possibility that unhealthy buildup of manganese in the body may lead to hyperactive behavior. This could, at least hypothetically, "push" an individual with the predominantly inattentive form of ADHD to more of a mixed or combined subtype of ADHD, which includes hyperactive/impulsive behavior as well. A study of French Canadian children who lived in an area with naturally high levels of manganese found a significant tie-in between high manganese levels and hyperactive behavior. A summary of that study can be found here. Some key points of the article (along with some of my thoughts and comments) are listed below:
Hair samples, while not a perfect method of evaluating manganese intake, is typically a good indicator of overall manganese exposure. This was the method used in the study of children in a region of Quebec, Canada with naturally high manganese levels in the drinking water. Children whose drinking water source came from a well with higher manganese levels showed consistently higher manganese levels in their hair samples.
46 children, ages 6-15 were examined in the study. Most were previously non-medicated and untreated for ADHD or related conditions before the study.
A strong positive correlation was seen between high manganese levels in the hair and oppositional behavior scores in the children, as based on the teacher rating scale mentioned above. This was done using a form of the revised Connner's Teacher rating scales (a common method used for diagnosing ADD, ADHD and related symptoms and behaviors). For a brief synopsis of the different elements or categories of Conner's rating scales, please click here. Briefly, oppositional is characterized by "angry" or "annoyed" temperament as well as "rule-breaking" behavior.
Additionally, an even stronger statistical correlation was seen between high manganese hair levels (above the study threshold level of 3 millionths of a gram of manganese per gram of hair sample, which was established based on detection methods and previous studies) and hyperactivity. Here, hyperactivity is characterized by restlessness and the inability to sit still, impulsive behavior and the inability to maintain adequate focus for a given task.
Every single child who displayed the necessary score to be considered "hyperactive" or "oppositional" had manganese levels above the study cutoff amount of 3 millionths of a gram of manganese per gram of hair. Additionally, a large majority (11 of 13), who tested above the critical score for ADHD risk had manganese levels above the cutoff mark mentioned above.
In contrast, cognitive problems (i.e. difficulty concentrating, slow learning, poor organizational skills) did not seem to be linked to manganese levels based on the study. Hypothetically, this suggests that high manganese exposure, should it be a factor in the onset and symptomology of ADHD, would likely be aligned or affiliated more with the hyperactive/impulsive subtype of ADHD and less towards the inattentive form of ADHD.
Interestingly, the high degree of connection between high manganese levels and hyperactivity or oppositional behavior was not present in an analogous Conners Parent rating scale as it was for the teacher rating scale. While it may be simply due to differences in observational patterns and previous history with the children (i.e. parents may be more "accustomed" to specific behaviors based on long-terms relationships, or may be less objective in identifying problem behaviors in their children for a study), this should raise some questions to the replicability of this study and its findings. Additionally, it is possible that some of these observed behaviors are more relevant to an academic setting, and solutions such as trying to reduce manganese exposure at home, may provide more benefits in the classroom than at home. None of these should be ruled out as possibilities.
*** Blogger's note: The following 2 points was addressed briefly in the manganese article, are rather long and complex and stray slightly off-topic. They can be omitted if necessary. Nonetheless, I think there are some interesting affiliations between this post, which deals primarily with manganese and common symptoms seen in ADHD and related disorders, and previous posts, which have dealt with genes associated with ADHD.
Signaling and proper communication in the nervous system is dependent on certain chemicals such as GABA (which is also important for proper muscle tone and function) as well as dopamine and their respective systems or "targets". These complex systems in the body have been shown to be effected by high manganese levels. The negative effects of high manganese exposure are thought to work through these very systems. A quick summary of a study done on this can be found here.
Interestingly, the very systems associated with these two agents ( GABA and dopamine ) are also thought to be affiliated with hyperactivity. A summary and link to the full article on this can be found here. Note that this study investigated a genetic connection between these systems and the onset of ADHD. Some of the genes indicated in this paper have been investigated in previous posts on this blog. Among these are the DRD4 gene, the DRD5 gene, and the DAT gene.
There appear to be slight but noticeable differences based on age and sex. Based on the teacher (but not parent) rating scales, older children appeared to have more severe symptoms of ADHD behavior, hyperactivity, cognitive impairment and oppositional behavior. While the effects were relatively small, there remains the possibility that cumulative exposure to elevated levels of manganese can lead to increased impairment over time. However, I am personally not comfortable in making this assertion based solely on the limited scope of this study.
What I did find interesting was the fact that girls showed substantially higher manganese concentrations in their hair samples than did boys. I am intrigued by the possibility that there may be hormonal reasons behind this, especially given the context of a previous post which mentioned that magnesium has a tendency to be stored better in females due to the effects of estrogen, and iron levels are thought to be lower in females due to menstruation as well as other effects.
While the study made several noteworthy observations, there are too many loose ends and questions left to be answered before determining whether manganese can pose similar risks to lead as far as inducing hyperactive behavior and ADHD-related symptoms. As of now, we are unsure whether the effects were do more to interference with iron absorption (given that numerous studies have shown that individuals with ADHD are typically iron deficient) or through a non-iron-based regulation of the GABA and dopamine pathways mentioned above. Further clouding this is the fact that iron itself plays a key role in dopamine synthesis and manufacturing.
As of now, my conclusion is that there is a possible correlation between high manganese and ADHD (especially the hyperactive form), but this connection is much weaker than that of lead (which is debatable in its own right at the moment). It certainly appears that manganese is more tolerable and overall more benign than lead, at least with regards to similar levels of exposure.
Unlike lead, manganese is actually a trace element micronutrient (i.e., it's good for the body at low levels). Manganese-rich foods include teas, beans, nuts and many types of whole grains. Additionally, excess manganese can be cleared more easily from the body than can lead. While common sources are food and drinking water (with water thought to be a more potent source of intake than food), inhalation is also a common mode of entry. This is especially true of specific occupations such as welders. Typical blood manganese levels hover around 1 microgram of manganese/deciliter of blood. This roughly translates into about .05 grams total manganese in the bloodstream.
It is easy and often tempting to try to assimilate anything and everything to a disorder such as ADHD. Many professionals and researchers often fall into this trap. However, I caution against this, since this clouds the picture as to what the real underlying causes of the disorder might be. That is why I urge restraint before passing judgment on this particular metal, at least in regards to its causative role with respect to ADHD and related disorders.
Certainly, manganese toxicity is a problem, with the deleterious effects of manganism (sometimes referred to as "manganese poisoning" and is characterized by loss of balance and coordination and impaired reaction timing) going back hundreds of years and still seen in certain metal-related occupations such as welding. Nevertheless, the relative ease of excretion of manganese (at least when compared to other heavy metals such as lead) and somewhat higher limits of tolerability make it a possible foe in the ADHD symptom world, but not a powerful one, at least for the time being.
In the next post, we will be shifting gears a bit and looking into the connection between celiac disease and ADHD and its degree of association with specific symptoms of the disorder.