As anxiety remains prevalent in patients after their cardiac events (Goodacre et al 2001
), progress was indicated in the participants by their significantly reduced anxiety scores after five sessions of beta training. The ability to generate alpha brainwaves has been associated with the self-regulation of stress (Wacker 1996
). Previous studies specifically linked anxiety and relaxation with EEG recordings (Isotani et al 2001
) and found that an increase in alpha frequencies in the frontal scalp area is an indication of positive relaxation training effects of audiovisual stimulation (Teplan et al 2003
) and is neuroprotective (Sterman et al 1970
As a whole, most participants had normal anxiety levels and this probably had some effect on the results of the EEG recordings particularly the alpha waves. Although alpha changes are tightly linked to anxiety changes, this is only evident in high-anxiety subjects as discovered by Hardt and Kamiya (1978)
. Their study showed that some people with high levels of anxiety have low alpha waves, and EEG alpha increase is beneficial only for patients who exhibit this low amplitude alpha. Patients with anxiety who show abnormally high levels of alpha at baseline readings do not respond as effectively to alpha increase biofeedback. Another important factor is that alpha waves attenuation is no longer evident with open eyes (Nakagome 2000
), and our subjects were instructed to keep their eyes open throughout their sessions. Another study also found no stimulation on the alpha band for participants that were asked to remain awake but with their eyes closed (Schutter et al 2001
Generally, patients undergoing beta training would have initial high beta frequencies of 22–40 Hz to be used for baseline comparisons. However, the beta bands for all our subjects during the recruitment stage were in the low SMR frequencies, which were below normal beta frequencies. This also suggests that these participants were not highly stressed at the initial diagnosis of their cardiac event during recruitment as excessive beta waves are associated with anxiety (Kiloh et al 1981
The significant difference in the mean anxiety scores between the participants and the control group for the second assessment suggests that EEG biofeedback can effectively lower mild to moderate levels of anxiety, thus making it ideal to be used in nonpsychiatric units, ie, cardiac settings. Biofeedback as a low arousal training methodology has been previously efficient in treating anxiety disorders (Rice et al 1993
). Inconsistencies in the different studies concerning anxiety reduction could be attributed to the way anxiety was assessed in individual patients and the actual length of treatment with longer periods of treatment reducing anxiety more effectively.
Detailed evaluation of each patient undergoing treatment would be a better evaluation of the characteristics and efficiency of the treatment. The Biograph program used for our study only required an electrode to be placed on only one active site in the scalp (C3) for EEG recordings. Most of the other similar studies recorded EEG from more than one active site according to the International 10–20 system. Furthermore, any increase in arousal affects the EEG frequencies in the entire region of the scalp and not just an isolated area (Barry et al 2004
). Changes in arousal levels are linked with global activity while specific regional activity is linked with processing. A comprehensive EEG recording from the global activity might give more details on the effect of EEG beta waves training on anxiety levels.
While the number of subjects participating was sufficient, the initial high dropout rate makes it difficult to conduct a double-blind study in which the one group of subjects are randomly assigned to EEG biofeedback and the other group to another type of biofeedback. Nevertheless, our study of 5 sessions of operant training of EEG activity was sufficient to produce significant changes in anxiety scores. Even in the subjects 2 group, those that dropped out by the third or fourth session were able to reduce their anxiety scores. A more detailed assessment would be to see the long-term effect of therapy, and evaluate whether a 3-month program could still have positive influence on anxiety 6 months or one year after completion of treatment.