A test of three psychophysiological theories on primary insomnia

The study was aimed at evaluating three hypotheses about primary insomnia: (a) insomniacs are physiologically more activated than controls (e.g. 1); (b) insomniacs respond with higher arousal to novel stimulation (arousability) (2); (c) insomniacs have a deficit in the de-activation processes (3). Twelve young insomniacs (F = 8, M = 4, mean-age = 22.66; SD = 4.33), and 11 good sleepers (F = 7,M = 4, mean-age = 22.54; SD = 2.20) participated in the study.Sleep parameters were monitored at home through sleep-logs and actigraphy for 1 week. Each night skin conductance levels (SCL), peripheral body temperature and heart interbeat-intervals (IBI) were recorded trough a portable device in a 3 min. baseline trial (BSL,) and in 2.5 min a STARTLE reflex trial. For each subject two nights were identified: the one with the worst sleep quality (N-) and the one with the best quality (N+). Hypotheses (a) and (c) were evaluated throughthree mixed 2 x2 x 2 ANOVAs in which dependent variables were the means of each parameter sampled during the first and last minutes of the BSL and factors were the GROUP (insomniacs, controls), theNIGHT (N-, N+), and the MINUTE (first, last). The arousability hypothesis was evaluated through 3 similar mixed 2 x2 x 2 ANOVAs analyzing data collected in the STARTLE trial. Significant and marginally significant results showed that insomniacs have slower deactivation rate and lower habituation to the startle stimuli before a bad night. References: 1. Monroe L.J. (1967). Psychological and physiological differences between good and poor sleepers. Journal of Abnormal Psychology, 71:255–264. 2. Lundh L.G., Broman J.E. (2000). Insomnia as an interaction between sleep-interfering and sleep-interpreting processes. Journal of Psychosomatic Research, 99: 299–310. 3. Espie C.A. (2002). Insomnia: conceptual issues in the development, persistence, and treatment of sleep disorder in adults. Annual Review of Psychology, 53: 215–243.