Depressed mood enhances anxiety to unpredictable threat

Abstract

Background: Depression and anxiety disorders (ADs) are highly co-morbid, but the reason for this co-morbidity is unclear. One possibility is that they predispose one another. An informative way to examine interactions between disorders without the confounds present in patient populations is to manipulate the psychological processes thought to underlie the pathological states in healthy individuals. In this study we therefore asked whether a model of the sad mood in depression can enhance psychophysiological responses (startle) to a model of the anxiety in ADs. We predicted that sad mood would increase anxious anxiety-potentiated startle responses.

Method: In a between-subjects design, participants (n=36) completed either a sad mood induction procedure (MIP; n=18) or a neutral MIP (n=18). Startle responses were assessed during short-duration predictable electric shock conditions (fear-potentiated startle) or long-duration unpredictable threat of shock conditions (anxiety-potentiated startle).

Results: Induced sadness enhanced anxiety- but not fear-potentiated startle.

Conclusions: This study provides support for the hypothesis that sadness can increase anxious responding measured by the affective startle response. This, taken together with prior evidence that ADs can contribute to depression, provides initial experimental support for the proposition that ADs and depression are frequently co-morbid because they may be mutually reinforcing.

Figure 1

Task schematic. Following a startle habituation procedure, subjects underwent a shock workup procedure followed by a neutral or negative Mood Induction Procedure (=MIP and -MIP, respectively), after which the threat of shock experiment started. The threat of shock consisted of three conditions, no shock (N), predictable shock only during cue (P), and unpredictable shock (U).

Figure 2

Anxiety – not fear - was facilitated by sadness. Anxiety is operationally defined as the difference in ITI startle magnitude between unpredictable shock and no-shock condition. Fear is operationally defined as the difference in startle magnitude between the ITI and cue of the predictable shock condition. Neutral and Sad represent neutral and sad mood induction procedures *p=0.03