A COMPARISON OF SLEEP EVENTS IN PTSD AND PD
There is evidence indicating that both PTSD and PD involve similar symptomatology indicative of frequent and chronic sleep disturbances, such as, recurrent awakenings, decreased sleep time and the occurence of nocturnal panic. Perhaps most distinctive is the apparent intrusion of arousal into the sleep state and the inability of PTSD and PD subjects to maintain diminished arousal for long periods of time. Nevertheless, there are important differences which reinforce the distinction between these diagnoses. First, the evidence demonstrates that the timing of awakenings with panic symptoms tends to occur at separate and discrete stages of sleep. Accordingly, it is possible that these disorders involve common neural pathways, but that they are triggered by different stimuli. Specifically, these stimuli would involve featurs of slow wave sleep in PD and features of REM sleep in PTSD. Furthermore, although PTSD subjects without comorbid PD
experience flashbacks with anxiety symptoms following lactate infusions, there is insufficient knowledge regarding qualitative differences in the panic attacks which occur with PD and PTSD to arrive at any definite conclusions (Jansen et al,1997). Consequently, although both groups appear to be sensitive to biological challenge and experience anxiety symptoms, the instruments currently employed to measure panic, such as the AAcute Panic Inventory, are not sensitive enough to differentiate cognitive and physiological symptom differences between these subject groups (Jensen et al,1997). Moreover, due to the difference in events which precede the onset of PTSD and PD, one might expect differences inthe qualitative nature of anxiety attacks in these disorders. For example, the PTSD falshback is viewed as "an expected response to reexperiencing a life-threatening situation" (Jensen et al,1997,268); whereas, the panic attack in PD is defined by its spontaneity and the absence of a threatening trigger (Jensen et al
,1997).
The evidence gathered to date has facilitated a less ambiguous understanding of sleep psychopathology and anxiety disorders, but there are still many questions which require further investigation. Consequently, future research should focus on specifying the differences between PTSD and PD anxiety symptoms, such as, distinguishing variations in the occurrence of nocturnal panic in populations of PTSD subjects compared with PD subjects. Other dirctions for researchers to pursue should include defining subsets of both PTSD and PD populations. For example, establishing whether it is the same population of PD patients which is triggered by biological challenge tests as that which experiences sleep-disordered breathing and whether PTSD patients with disordered breathing are a distinct subset with comorbid PD (Stein, Millar, Larsen & Kryger,1995). It is also essential that the mechanisms responsible for the inability to maintain low levels of arousal in both PTSD and PD be identified so that adequate treatments can be developed. Additionally, the role of recurrent stressors and traumatic memories in the maintenance of PTSD and PD should be examined. This seems especially important in light of several findings related to levels of daily functioning, including data demonstrating that:
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