ANXIETY
In a 1992 review of the literature (1), it was concluded that “it appears that caffeine can increase anxiety when administered in single bolus doses of 300 mg or higher, which is many times greater than the amount present in a single serving of a typical caffeine-containing beverage. However, in lower doses it appears to have little effect on this mood-state or, under certain circumstances, it may even reduce anxiety levels.”
Since this review was published two studies have confirmed that high doses of caffeine promote anxiety. Thus 600 mg caffeine (2) or several cups of coffee each containing 125 mg caffeine (3) increased anxiety. Caffeinism has been defined as a group of symptoms associated with daily intakes of caffeine of 1000-1500 mg which closely resemble the symptoms of severe chronic anxiety. However, there is little evidence in the literature of associations between caffeine intake and anxiety. Intervention trials with normal doses of caffeine have not shown effects on anxiety either in healthy subjects or in psychiatric patients with anxiety disorders. In addition, caffeine has not been shown to increase the anxiety induced by other stressors. Hence there is no reason to modify the conclusions of the 1992 review on effects of caffeine on anxiety (1).
References:
1. Liebermann, H.R. Caffeine. In: Smith, A.P. and Jones, D.M. (Eds.), Handbook of Human Performance, vol. 2.Academic Press, London, pp. 49-72, 1992.
2. Sicard, B.A. et al. Aviation, Space, and Environmental Medicine, 67, 859-862, 1996.
3. Green, P.J. and Suls, J. Journal of Behavioral Medicine, 19, 111-128, 1996.