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 (T) and heart interbeat-intervals (IBI) were recorded trough a portable device in a 3 baseline trial (BSL,) and in 2.5 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 through three mixed 2 · 2 · 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), the NIGHT (N), N+), and the MINUTE (first, last). The arousability hypothesis was evaluated through 3 similar mixed 2 · 2 · 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.