Electrophysiological measures have mainly been used to assess the side effects of interferon treatment on cognitive and psychological function in patients with hepatitis B and C (Tanaka et al, 2004). In one of the earliest reports of this kind, hepatitis C patients who were treated with interferon-alpha had higher delta, theta-1, and theta-2 power values, and lower alpha-2 and beta power values as measured by EEG (Kamei et al, 2002). These changes were recorded when comparing baseline values to those obtained during the course of treatment. Another study compared baseline EEG recordings and psychological functioning to that assessed at various time points during interferon treatment in hepatitis B
and C patients, abnormal EEG activity (e.g., general slowing of the basic rhythm and of the alpha wave) was associated with increased incidence of various psychological symptoms including mania, depression, and sleep disorders (Tanaka et al, 2004). This association appeared to be independent of multiple medical or treatment factors. Amodio et al (2005) confirmed the general slowing of the mean dominant frequency in hepatitis C patients and also observed increases in frontal alpha power and parietal theta power. These results, unlike those of Tanaka et al (2004), were unrelated to cognitive or other psychological factors.
This group of studies largely supports the contention that interferon treatment given to hepatitis patients influences EEG activity; however, it remains unclear what effects, if any, these changes may have on cognitive and psychological function. Variation in the precise brain indices related to treatment limit inference, but likely relate to variation in measurement, differences in instruments used, and participant differences (which were often not well described).
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