Schizophrenia Bulletin Advance Access published online on May 8, 2009
Schizophrenia Bulletin, doi:10.1093/schbul/sbp028
Concurrent Measurement of "Real-World" Stress and Arousal in Individuals With Psychosis: Assessing the Feasibility and Validity of a Novel Methodology
2 Department of Psychiatry, Columbia University, New York, NY
3 New York State Psychiatric Institute, New York, NY
4 Departments of Psychiatry and Neuropsychology, Maastricht University, Maastricht, The Netherlands
5 Department of Applied Mathematics and Statistics, State University of New York (SUNY), Stony Brook, NY
6 Department of Psychiatry, New York University Medical Center, New York, NY
1 To whom correspondence should be addressed; Department of Psychiatry, Box 55, Columbia University, 1051 Riverside Drive, New York, NY 10032; tel: 212-543-6817, fax: 212-543-6176, e-mail: dk553{at}columbia.edu.
Background: Psychosis has been repeatedly suggested to be affected by increases in stress and arousal. However, there is a dearth of evidence supporting the temporal link between stress, arousal, and psychosis during "real-world" functioning. This paucity of evidence may stem from limitations of current research methodologies. Our aim is to the test the feasibility and validity of a novel methodology designed to measure concurrent stress and arousal in individuals with psychosis during "real-world" daily functioning. Method: Twenty patients with psychosis completed a 36-hour ambulatory assessment of stress and arousal. We used experience sampling method with palm computers to assess stress (10 times per day, 10 AM 
10 PM) along with concurrent ambulatory measurement of cardiac autonomic regulation using a Holter monitor. The clocks of the palm computer and Holter monitor were synchronized, allowing the temporal linking of the stress and arousal data. We used power spectral analysis to determine the parasympathetic contributions to autonomic regulation and sympathovagal balance during 5 minutes before and after each experience sample. Results: Patients completed 79% of the experience samples (75% with a valid concurrent arousal data). Momentary increases in stress had inverse correlation with concurrent parasympathetic activity (
= –.27, P < .0001) and positive correlation with sympathovagal balance ( = .19, P = .0008). Stress and heart rate were not significantly related ( = –.05, P = .3875). Conclusion: The findings support the feasibility and validity of our methodology in individuals with psychosis. The methodology offers a novel way to study in high time resolution the concurrent, "real-world" interactions between stress, arousal, and psychosis. The authors discuss the methodology's potential applications and future research directions.
Keywords: psychosis / schizophrenia / stress / arousal / heart rate variability / vagal / cardiac autonomic regulation / experience sampling method / palm computers