Generalized anxiety disorder consists of excessive worry about many issues combined with an inability to control that worry. Other symptoms include sleep disturbance, restlessness, irritability and being easily fatigued. Genes seem to play a role, as do stressful events and learned behavior. Treatments may include antidepressants that work on the serotonergic system and cognitive-behavioral therapy. In the last few years, there has been an interest in zinc as a possible treatment for this condition.
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Zinc and Childhood Anxiety
A study reported in the November 2010 issue of the "American Journal of Clinical Nutrition" examined the effects of zinc supplementation on Guatemalan children. An earlier study defined children having serum zinc levels of below 75 micrograms per deciliter as being zinc-deficient. In this study, one-fifth of the children had zinc levels below 65 micrograms per deciliter.
Children were randomly assigned to either a group that received zinc supplementation or a group that received a placebo. At the end of the study, even the children who did not receive zinc had higher plasma levels of this mineral than they did when the experiment started.
When children were evaluated for depression, anxiety, hyperactivity and conduct disorder, the researchers found that there were no significant differences between the zinc and placebo groups on any measure of mental health used in the study. However, when children were studied individually, it was found that higher zinc levels were correlated with lower levels of depression and anxiety.
Revew of Zinc Studies
A November 2010 article published in "Current Opinion in Clinical Nutrition & Metabolic Care" reviewed studies on zinc and mood disorders. Animal studies showed that zinc reduced symptoms of depression and anxiety. Clinical studies with humans have found that zinc levels tend to be low in depressed patients. Supplementation improved their responsiveness to antidepressants and may be particularly valuable for treatment-resistant patients. There is no indication, however, that zinc supplements would benefit depressed people who already have adequate levels of this mineral. Since depression and anxiety are thought to be closely related disorders and since many of the same medications used for depression are also used to treat anxiety, this finding may have relevance for the treatment of anxiety.
Why Zinc May Alleviate Anxiety
Enzymes containing zinc are necessary for the synthesis of serotonin. Since many of the current pharmacological treatments for anxiety act on the serotonergic system, the implication is that a severe zinc deficiency could lead to a reduction in serotonin synthesis and an increase in anxiety.
A second neurotransmitter, gaba-aminobutyric acid (GABA), regulates mood states. In fact, some of the older medications for treating anxiety like Valium and Xanax work by binding to GABA-nergic receptors in the brain. Zinc stimulates one of the crucial enzymes, pyridoxal kinase, involved in the synthesis of this neurotransmitter.
Effects of Too Much Zinc
Higher levels of zinc do not necessarily reduce anxiety. In fact, too much zinc can have the opposite effect, according to the results of animal research published in the May 11, 2010 edition of "Physiology & Behavior." In this study, rats were given either plain water, zinc in various concentrations or a combination of zinc and copper. Compared to rats given water only, the zinc-only rats showed more anxiety, as measured by their tendency to "freeze" under stress. The zinc-only rats also showed impaired memory on a task requiring them to swim to an underwater platform whose location was rendered invisible by adding powdered milk to the water. In contrast, the rats given both zinc and copper performed as well as the rats given water only. These results do not prove that zinc causes anxiety or memory loss, but they do indicate that a proper balance of zinc and copper is necessary for optimum mental functioning.
If you are considering taking zinc to treat anxiety, it is important to realize that it may not help you if your zinc levels are already within normal range. Zinc, like other minerals, is beneficial in proper amounts but toxic in large doses. Unless you are pregnant or nursing, the recommended daily allowance of zinc is 11 mg. You should never take more than 40 mg per day under any circumstances and should always consult your doctor before taking more than the recommended daily allowance of any nutrient.