Joao G. Ribeiro, Department of Psychiatry, Hospital Prof. Doutor Fernando Fonseca EPE, Amadora, Portugal
Carlos Lourenco, Universidade de Lisboa, Portugal

Abstract: Individuals with affective disorders show losses in the complexity of their mood variation. We hypothesized that this complexity is a mechanism by which resilient individuals respond to everyday-life adversity, a response that would be disrupted in patients with affective disorders. Participants were outpatients with affective disorders (N=17) and matched controls (N=10) who self-recorded their daily mood over a mean duration of 233 days. Complexity was measured by sample entropy. The load of adversity was conveyed by the proportion of severely negative-affective days. Results showed that, in both controls and patients, complexity increased with adversity but patients displayed substantial disruptions in this complexity response by: (a) weaker associations between complexity and adversity (Pearson s r=0.54 to 0.59 vs. 0.59 to 0.70);(b) lower complexity for the same load of adversity (ANCOVA, p<0.01), representing losses of up to 29% of the complexity expected from controls (Mann-Whitney, p<0.005). We concluded that patients with affective disorders fail to increase the complexity of their mood variation to the same extent as resilient individuals when exposed to the same load of adversity, and propose that rigid emotion regulation processes may be causing this attenuated response. Resilience implies complex mood for complicated lives.

Keywords: depression, bipolar disorder, nonlinear dynamical systems, entropy, resilience, emotion regulation