Harvey noted that
insomnia is often viewed to be epiphenomenal to or a byproduct of the primary mental disorders.
However, the author concluded after a review of current research that insomnia may be a primary
cause (both onset and relapse) and contributor to the maintenance of mental health disturbances,

Experimental observations of LRTCs estimated
over phase synchronization in EEG/MEG signals suggest that the main driving mechanism of the
observed avalanche activity is global where all temporal scales contribute to the characteristic
system behavior (Botcharova et al., 2014). LRTCs have been reported as being impaired in
epilepsy (Monto et al., 2007), Alzheimer’s disease (Montez et al., 2009), schizophrenia (Nikulin
et al., 2012), major depressive disorder (Linkenkaer-Hansen et al., 2005), post-traumatic stress
disorder (PTSD) (Ros et al., 2015; for reviews see Cohen et al., 2010 ) and in age-related
cognitive disorders (Mishra and Gazzaley, 2014) and, for that reason, a closed-loop
neurofeedback approach could be a valuable tool for non-pharmaceutical treatment (Zhigalov et
al., 2016).
Conflict of

In this review we summarize the main outcomes and find that there
are consistencies between these studies, but also many inconsistencies that
make obvious the need of a unified line of investigation. We also propose some
suggestions for the future in order to improve our knowledge about LRTC and
depression.