Dynamic complexity of positive and negative affect in NSSI – A daily diary study

Background: Non-suicidal self-injury (NSSI) is a major health problem. Previous studies have shown that NSSI is related to affect instability and increased affective intensity. While the role of negative affects has already been extensively explored, only few studies have investigated the relationship between intensity, stability, and other characteristics of positive affects and NSSI. The concept of dynamic complexity (DC), derived from the theory of nonlinear systems, is particularly well suited to analyze the dynamics of the affect in a differentiated manner by means of ecological momentary assessment (EMA). Accordingly, this study examines DC of positive and negative affects in individuals with and without a NSSI history in an EMA setting. Method: Participants from a clinical NSSI group (n = 28) and a comparable control group without NSSI (n = 33) worked on the Positive and Negative Affect Schedule (PANAS) once a day between six and 37 days (M = 15.60, SD = 5.80). DC was calculated multiplying intensity and fluctuation indices of the daily affect. Results: Persons with a history in NSSI had a higher dynamic complexity in affect in general as well as in positive and negative affect compared to control persons. In addition, the NSSI group reported more positive affect compared to the controllers. Conclusions: These results suggest that it is important to assess dynamic emotional patterns and analyze in detail the role of both positive and negative affects in individuals with a history of NSSI in order to better understand the complex interplay between the different emotional states and to be able to use it for diagnostic purposes and clinical interventions.