Sleep–wake cycles and cognitive functioning in schizophrenia

Abstract

Consolidated circadian rhythms and sleep may be a prerequisite for adequate cognitive functioning in individuals with schizophrenia.

Sleep dysfunctions in schizophrenia: A practical review

“…The timing, and architecture, of sleep have been linked to performance on broad neuropsychological tests in SZ. Deficits on test of attention and response times are the most commonly reported findings [10], and are in agreement with the literature in healthy people showing that sleep deficits cause reliable reductions in speed of processing and attention. Increasing evidence also links impairments in slow waves and sleep spindles with attention [46], but not with general cognitive ability.…”

“…As noted above, investigations of circadian rhythm chronobiologic parameters in SZ have identified dysregulation of the SCN, including abnormal 24-hr rhythms (phase advance) of melatonin and serotonin, body temperature, cortisol, and prolactin e.g. [9,11,12,35,52]. In addition to the role of serotonin dysfunctions, deficits of the inhibitory neurotransmitter gamma amino butyric acid (GABA) may play a role in SZ sleep dysfunctions.…”

“…The evidence also suggests that reduced sleep duration is more commonly reported in neuroleptic-naive or drug-free individuals, while a longer need for sleep is reported in medicated samples [4,8], consistent with drug studies demonstrating the sedative properties of antipsychotic medication. Investigations of circadian rhythm chronobiologic parameters in SZ also point to disruptions in the internal biological clock of patients, showing dysregulation of the suprachiasmatic nucleus (SCN) and abnormal levels of melatonin [9][10][11][12]. Insomnia has been noted as one of the earliest clinical symptom that heralds the onset of psychosis, and possibly relapse [13], yet these sleep symptoms are not pathognomonic for the disorder.…”

“…While these findings promote the positive effects of antipsychotics on sleep, abnormalities of sleep timing and architecture still persist when compared non-psychiatric controls. For example, neurobiological circadian parameters and sleep spindle abnormalities remain uncorrected [9,12,35]. In addition, a recent study examined the relationship between the number (and dosage) of antipsychotic medications and sleep in a psychiatric inpatient population including SZ patients.…”

Investigation of genetic variants in ubiquitin enzyme genes involved in the modulation of neurodevelopmental processes: a role in schizophrenia susceptibility?

“…Furthermore, the circadian pattern of FBXL21 expression in the mouse suprachiasmatic nucleus (region responsible for controlling circadian rhythm) is reminiscent of the expression pattern seen for other circadian pacemaker genes such as Period 1 (PER1) (Dardente et al, 2008). Mutations in either the FBXL21 or FBXL3 genes can lead to a dysfunction of circadian rhythm oscillations and lead to significant behavioral disturbances in individuals and alterations in their sleeping patterns; moreover the absence of FBXL21 causes a short-period phenotype in both mice and cells (Hirano et al, 2013;Yoo et al, 2013 (Bromundt et al, 2011); which is further supported by a microarray study which found a significant downregulation of the circadian pacemaker gene PER1 in the postmortem temporal cortex of schizophrenia patients compared to healthy controls (Aston et al, 2004). Furthermore, an animal model study has shown dysfunction in the synchronization of circadian rhythms between brain cell networks involved in sleep-wake regulation and cognition (Dudley et al, 2003).…”