Beta-blockers are a class of drugs that selectively compete for and inhibit binding at the beta-adrenergic subset of receptors of the sympathetic nervous system (Middlemiss et al., 1981; Patel & Turner, 1981). Beta-adrenergic receptors are primarily located in the heart and in the smooth muscle of the blood vessels and the lungs, but also exert metabolic and other effects. The beta-blockers are structurally similar to the body's adrenergic neurotransmitters, norepinephrine and epinephrine, and they exhibit their greatest effects during periods of intense sympathetic nervous system (SNS) activation. Therefore, the most common clinical use of these drugs is for the treatment of cardiovascular disorders, including hypertension and manifestations of ischaemic heart disease such as angina pectoris and cardiac arrhythmias (Frishman, 1980; Patel & Turner, 1981; Weiner, 1985).

However, since the introduction of these drugs and their wide therapeutic use, a variety of both desirable and unwanted psychological effects have been observed. One of the most frequently noted beneficial effects has been the reduction of reported anxiety by individuals in certain acutely stressful situations (e.g. performing before an audience or dental surgery) that are normally accompanied by several somatic manifestations of arousal (Frishman et al., 1981; Noyes, 1982; Elman et al., 1998). There have also been some reports that chronic beta-blocker therapy might lessen anger and irritability or ‘coronary-prone’ behaviour pattern (Schmeider et al., 1983; Krantz & Durel, 1983; Fedorets et al., 2004).