| Anxiety disorders and depression are some of the most frequently comorbid and confusingly intertwined psychological conditions (Kessler, Chiu, Demler, & Walters, 2005; Brown, Campbell, Lehman, Grisham, & Mancill, 2001). They share some observable characteristics but also have qualities that seem more exclusive to one or the other. The difficulty of making an accurate diagnosis is further complicated by the inaccuracies of self-report and changing clinical criteria. Psychophysiological methods may serve as an additional or converging means of distinguishing between anxiety and depression. The current study attempts to establish an easily observable difference between the two using electromyographic (EMG) and skin conductance response (SCR) measurements of the acoustic startle response (ASR) and its related phenomena of prepulse inhibition (PPI), habituation, and dishabituation. Evidence exists for increased startle (Ludewig et al., 2005) and decreased habituation and PPI (Ludewig, Ludewig, Geyer, Hell, & Vollenweider, 2002) in persons with anxiety-related disorders but no such effects in persons with non-psychotic depression (Taiminen et al., 2000; Ludewig & Ludewig, 2003). In addition, depression has been associated with low SCR (Argyle, 1991) and anxiety with high SCR (Roth et al., 1990; Doberenz et al., 2010). We hypothesized that participants who report themselves high on anxiety but not depression will have increased ASR and SCR and decreased PPI and habituation compared to those who report themselves high on depression but not anxiety and compared to a control group. Further hypotheses stated that participants high on depression but not anxiety would show lower SCR and decreased ability to regain startle magnitude following a novel tone compared to high anxiety and control groups. One-way ANOVAs indicated no significant differences among groups on the basis of ASR, PPI, habituation, or SCR. Hierarchical regressions indicated that habituation significantly predicted a small percentage of variance in total depression and total anxiety scores such that persons with lower percentages of habituation were likely to score higher on measures of both depression and anxiety. Future studies should further investigate the relationship of startle habituation to anxiety and depression, preferably using a clinical sample of participants for greater power to detect effects. |
