Abstract
Aim
To assess plasma zinc and copper levels in individuals with anxiety and to test the hypothesis that there is a relationship between copper and zinc concentration and improved symptoms.
Subjects and Methods
Serum from 38 individuals with anxiety and 16 neurotypical age, gender and size similar controls were tested for plasma zinc and copper concentration using inductively-coupled plasma-mass spectrometry. Zinc and copper levels, pre and post therapy, were compared and assessed for perceived anxiety symptoms.
Results
In this preliminary study, individuals with anxiety had significantly higher plasma levels of Cu (P = 0.0348), Cu/Zn (P = 0.0493) and lower Zn (P = 0.0294) compared to controls. Zn levels normalized (increased to the normal range) and Cu/Zn significantly decreased after zinc therapy (P = 0.0004, P = 0.0033, respectively), but Cu did not significantly decrease (0.3577). These same patients improved significantly with respect to perceived overall symptoms after zinc and anti-oxidant therapy (P = 0.013).
Discussion
These results suggest an association between Zn plasma levels and individuals with anxiety, demonstrate that zinc therapy is effective in increasing zinc plasma levels, and show that zinc supplementation may play a role in improved symptoms.
Introduction
Anxiety is a normal emotional response to a threat or potential threat. However, when this emotion is inappropriate, extreme and persistent, and is not proportionate to the nature of the peril, it is classified as pathological.1,2 In response to threatening situations, the feeling of anxiety is usually accompanied by emotional stress, which involves behavioral, expressive and physiological features, such as an avoidance of the source of the danger, assuming defensive postures and increasing blood pressure, respectively.1,3
Anxiety disorders are the most common class of psychiatric disorders in the US 4 and many other countries.5–8 Yet, population-based studies have shown that this disease frequently goes untreated.9,10 Anxiety is implicated in a number of psychiatric disorders, such as depression, panic attacks and post-traumatic stress disorder 2 and affects approximately 30% of the US population, 4 and one-eighth of the total population worldwide. 11 This imposes a social burden that amounts to billions of dollars each year. 12
Zinc has a unique and extensive role in biological processes. Since the discovery of this element as an essential nutrient for living organisms,13–15 many diverse biochemical roles for it have been identified. These include roles in enzyme function, 16 nucleic acid metabolism,17,18 cell signaling 19 and apoptosis. 20 Zinc is essential for physiological processes including growth and development, 21 lipid metabolism, 22 brain and immune function.21,23
Dietary factors that reduce the availability of zinc are the most common cause of zinc deficiency, however, inherited defects can also result in reduced zinc. Both nutritional and inherited zinc deficiency produce similar symptoms, such as dermatitis, diarrhoea, alopecia and loss of appetite. 24 With more prolonged deficiency causing growth impairment and neuropsychological changes such as emotional instability, irritability and depression.25–28
Low intracellular zinc has been found to be associated with DNA damage, oxidative stress, antioxidant defenses, and DNA repair,29,30 and zinc may serve as an important anti-oxidant. 31
Because of the potential association between zinc and the etiology of neurological diseases, we tested patients with anxiety for plasma zinc concentration, and compared those levels with perceived symptoms, pre and post zinc therapy.
Materials and Methods
Subjects
Experimental and controls
Serum from individuals with diagnosed anxiety (N = 38; 18 female; mean age 35.1 +/- 19.2 years; mean weight 141.2 +/- 48.8 lbs) and controls (N = 16; 8 female; mean age 41.3 +/- 27.4 years; mean weight 145.3 +/- 43.3 lbs) was obtained from patients presenting at the Health Research Institute/Pfeiffer Treatment Center. There was not a significant difference in age (P = 0.23) or weight (P = 0.77) between experimental and control individuals. Most of individuals with anxiety were diagnosed using The Hamilton Rating Scale for Anxiety before presenting for treatment at the Pfeiffer Treatment Center, Warrenville, Il*.
The Pfeiffer Treatment Center is a comprehensive treatment and research center, specializing in the care of neurological disorders, including anxiety.
When comparing anxiety patients who were not taking drug therapy (N = 20) with those taking therapy (SSRIs (N = 6), anti-anxiety (N = 4), anti-convulsants (N = 2), stimulants (N = 2), blood pressure medication (N = 4), and sedatives (N = 2)), there was no significant difference in Cu (P = 0.636), Zn (P = 0.14904), Cu/Zn (P = 0.555), overall symptoms (P = 0.467) or specific anxiety symptoms (P = 0.841).
Patient consent was obtained from all patients involved in this study and this study was approved by the IRB of the Health Research Institute/Pfeiffer Treatment Center*.
Severity of disease
A modified Hamilton Scale was used to determine the severity of depression. Patients were asked to rate their depressive behavior such as; irritability and anger, lack of ability to focus/concentrate, racing thoughts, trouble sleeping, light sensitivity, migraines, OCD behavior, intrusive thoughts, overall anxiety, disorganization, panic, obsessive behavior, and overall anxiety. The patients were rated on a scale of 0-5 (5 being the most severe) for each of these behaviors. We evaluated the overall severity of anxiety behavior by establishing the mean of all of the scores for each patient.
Zinc and anti-oxidant therapy
Individuals in this study who presented to the Pfeiffer Treatment Center with anxiety were tested for zinc, copper and anti-oxidant levels. Based on deficiencies, they were then prescribed the appropriate dose of anti-oxidants. Pre-therapy patients represent those who were tested when they first presented and were not previously taking any zinc or anti-oxidants. Post-Therapy patients received anti-oxidant therapy (Vitamin C, E, B-6 as well as Magnesium, and Manganese if warranted), and zinc supplementation (as zinc picolinate), daily, for a minimum of 8 weeks.
Plasma
All experimental and control plasmas were treated in an identical fashion. Blood was drawn into tubes containing EDTA as an anti-coagulant, refrigerated and sent to LabCorp, Naperville Il for separation and analysis.
Copper and zinc serum concentration
Copper and zinc plasma concentration was performed by LabCorp, Inc. (Naperville, IL 60563) using inductively-coupled plasma-mass spectrometry, as previously described. 32
Statistics
Inferential statistics were derived from t-test with 95% confidence intervals.
Results
Individuals with anxiety had significantly higher plasma levels of Cu (P = 0.0348), Cu/Zn (P = 0.0493) and lower Zn (P = 0.0294) compared to controls (Table 1).
Cu, Cu/Zn and Zn serum concentration (mg/dL) in anxiety patients compared to controls.
Twenty of the 38 anxiety patients (chosen randomly) were given zinc and vitamin B-6 therapy. Zn levels normalized (increased to the normal range) and Cu/Zn significantly decreased after zinc and B-6 therapy (P = 0.0004, P = 0.0033, respectively), but Cu did not significantly decrease (0.3577) (Table 2).
Cu, Cu/Zn and Zn serum concentration (mg/dL) in anxiety patients pre and post therapy.
Symptoms (a scale of 1 to 5; 5 being the most symptomatic) of these same patients improved significantly post therapy (P = 0.013) (Table 3).
Anxiety symptoms pre and post therapy.
Discussion
The results reported here support previous findings of our lab and others who have found zinc deficiency in patients with depression,33–35 and anxiety, 36 and have suggested zinc homeostasis for possible therapy.37–39
In addition, elevated copper has been associated with women having a history of post-partum depression 40 and clinical depression has been associated with high copper in patients with Wilson's disease. 41
There is much support for the role of GABA and glutamate in mood disorders, particularly anxiety and depression. 42 Zinc has also been found to be associated with GABA and glutamate regulation, particularly through anxiolytic activity, modulating GABAergic inhibition and seizure susceptibility.43–45 Zinc deficiency has also been found to be associated with GABAergic impairment. 46
Zinc is well known as one of the most important trace elements in the body. Dietary zinc deficiency is associated with a variety of physiological defects including anorexia, skin lesion, and growth retardation. 47 Mechanistic studies demonstrated that zinc deficiency affects a large number of hepatic genes involved in multiple cellular functions. In particular, zinc deficiency has been shown to down-regulate hepatic gene expression of metallothionein (MT), insulin-like growth factor I (IGF-I), insulin-like growth factor binding protein 1 (IGFBP1), cyclin D1, and HGF, which are involved in cell proliferation.48–50
Studies have shown a potential association between oxidative stress and the etiology of anxiety. As an example, oxidative stress-related anxiety can be reversed in mice upon inhibition of NADPH oxidase or phosphodiesterase-2, enzymes that are indirectly implicated in oxidative stress mechanisms. 51 Surprisingly, diazepam, a well-known anxiolytic, does not fully reverse oxidative stress-related anxiety. 51 These results point to a possible utility for antioxidants in the prevention or reduction of anxiety. Further research will be necessary to show whether anxious subjects need more antioxidants than non-anxious subjects. Recent work51,52 has shown that some dietary polyphenols have both anxiolytic and antioxidant effects, which may be beneficial to anxious subjects. The potential relationship between oxidative stress and anxiety may generate interest in antioxidant therapy.
Zinc supplementation has also been found to prevent liver cell injury through attenuation of oxidative stress, 53 and there is evidence suggesting that alcohol-induced liver damage initiates hepatocyte proliferation, and zinc supplementation accelerates liver regeneration, through up-regulating cell proliferation-related proteins. 54
Based on the results presented in this study, we suggest that the low levels of zinc, possibly associated with concurrent oxidative stress, may cause lower GABA and glutamate, having an anxiogenic effect, and that zinc supplementation, raising GABA levels, may help improve anxiety symptoms. To evaluate this possible association, future studies will assess more patients with anxiety and evaluate GABA and glutamate levels along with zinc concentration, pre and post zinc therapy.
Disclosure
This manuscript has been read and approved by the author. This paper is unique and is not under consideration by any other publication and has not been published elsewhere. The author and peer reviewers of this paper report no conflicts of interest. The author confirms that they have permission to reproduce any copyrighted material.