Robert W. Bond, Jr., Marquette University, Milwaukee, WI
Stephen J. Guastello, Marquette University, Milwaukee, WI

Abstract: A dynamical disease is one in which the symptoms appear and disappear over time in a deterministic pattern that could be chaotic. By determining the dynamic structure of the temporal pattern it would be possible to gain some insight into the triggers for symptoms if not the disease process as a whole. The present study investigated whether obsessive-compulsive disorder (OCD) could be considered a dynamical disease because of the intermittent outbursts of ritual behaviors. One-week diaries were collected from 17 clinical cases with 16 matched controls to record both the occurrence of rituals as they transpired over time and the influence the family may have had upon the spatiotemporal structure of symptoms. Comparisons of nonlinear regression parameters and Lyapunov exponents revealed that OCD exhibited a low-dimensional deterministic structure. The average nonlinear model (R2 = 0.32) explained more than 10 times the variance of its linear counterpart (R2 = 0.03). Family reactions and emotional responses accounted for only a very modest increase in the variance explained by the nonlinear regression model or in the amount of turbulence. Family reactions and emotional responses do little to make the rituals go away, but instead may strengthen the dynamics. Finally, significant rank order correlations were found between the R2 for the time series for each logbook and Lyapunov exponents with symptom severity and family reactions.

Keywords: obsessive-compulsive disorder, dynamical disease, aperiodic, deterministic, diary method, Lyapunov, nonlinear regression