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Dynamics of violence.

RATIONALE, AIMS AND OBJECTIVES
Three behavioural models suggest different dynamic patterns of intimate partner violence (IPV). However, few studies permit assessment of IPV dynamics. The purpose of this study was to estimate the degree of non-linearity in daily violence between partners over a 3-month period, identify their specific dynamic patterns and determine whether measures of violence severity and dynamics are interrelated.


METHODS
From six primary care clinics, we enrolled 200 adult women who experienced violence in the previous month and asked them to complete daily telephone assessments of household environment, marital relationship and violence using Interactive Verbal Response. To assess non-linearity of violence, algorithmic complexity was measured by LZ complexity and lack of regularity was measured by approximate entropy. Lyapunov exponents and correlation dimension saturation were used to approximate dynamic patterns.


RESULTS
Of the 9618 daily reports, women reported experiencing abuse on 39% of days, while perpetrating violence themselves on 23% of days. Most (59%) displayed random dynamics, 30% showed chaotic and 12% showed periodic dynamics. All three measures of non-linearity consistently demonstrated non-linear patterns of violence. Using multivariate analysis of variance, neither episode severity for men or women showed significant differences across dynamic types, but chaotic dynamics had the lowest frequencies of violence in men and women while random dynamics had the highest frequencies. Approximate entropy was positively correlated with violence frequency and burden in men and women, but Lyapunov exponent was inversely related to violence. LZ complexity correlated positively with wife-perpetrated violence only.


CONCLUSIONS
IPV is rarely a predictable, periodic phenomenon; no behavioural model describes the violence dynamics for all violent relationships. Yet, the measures of non-linearity and specific dynamic patterns correlate with different violent features of these relationships.