Attention Deficit/Hyperactivity Disorder (ADHD)
Causes and Risk Factors
No single factor has been identified as a definitive cause of ADHD. Instead, most scientists believe that several variables influence ADHD risk. For example, genetics, exposure to stressors during pregnancy or infancy, early social interactions, and environmental toxins all appear to affect ADHD risk (Thapar 2013).
A considerable portion of ADHD cases are thought to be attributable to genetics and heritability (Neale 2010). A number of specific genetic variations are associated with ADHD. These are predominantly related to the regulation of dopamine (ie, a chemical messenger used by brain cells) (Faraone 2006; Thapar 2013; Franke 2012). The importance of dopamine in ADHD is highlighted by the fact that methylphenidate is thought to treat ADHD symptoms in part by increasing dopamine signaling in the brain (Volkow 2005).
Environmental toxins such as polychlorinated biphenyls, some pesticides, and lead have been linked to ADHD development, but no studies have proven that they directly cause the condition (Thapar 2013).Other external factors, such as negative child-parent interactions and poor or lacking early social contact, have been found to have a contributory effect in ADHD onset (McLaughlin 2010; Thapar 2013). Some variables in utero (in the womb) are seen as risk factors, but not causative links to ADHD. These include maternal smoking during pregnancy, premature birth and/or low birth weight, and/or maternal stress (Thapar 2013).
Traumatic brain injury has been linked to behaviors similar to those observed in ADHD (Eme 2012; NIH 2013a). Approximately 20–50% of children who suffer a traumatic brain injury develop a form of clinically relevant attention disorder termed secondary ADHD (Senior 2013; Ornstein 2013; Sinopoli 2011).
There is some evidence that deficiencies in certain nutrients, such as zinc, magnesium, and polyunsaturated fatty acids may be linked to ADHD (Thapar 2013). As will be discussed later in this protocol, studies have found evidence for insufficiency or imbalance of omega-3 and omega-6 fatty acids in people with ADHD (Colter 2008). Zinc and magnesium intake have also been found to be reduced in those with ADHD (Dura Trave 2013). Additionally, there is some evidence that high levels of ingested food additives such as artificial coloring (eg, tartrazine (E103), quinolone yellow (E104), sunset yellow (E110), carmoisine (E122), ponceau 4R (E124) and allura red (E129)) correlate with increased activity in children and therefore may exacerbate this symptom in those with ADHD (Stevens 2013). Excessive sugar intake has often been linked to ADHD as well, although the majority of research has largely debunked this as unsubstantiated; definitive evidence for a causal relationship is currently lacking (Johnson 2011). Nevertheless, it is generally advisable to limit sugar intake, as high sugar consumption may contribute to numerous other health detriments.