Altered immunity may have destructive consequences for the integrated central nervous system. This immune response often affects progressive neurodegenerative diseases such as Parkinson’s disease and/or psychiatric disorders such as schizophrenia. In particular, schizophrenia pathogenesis may be mediated by multiple neuro-immune interaction pathways. Gut microbiota might affect the brain and/or immune function. Significant machineries of immunity are commonly affected by the commensal gut microbiota. Therefore, schizophrenia may be connected with the gut-immune system. In addition, the brain and immune systems cooperate on multiple levels. The brain could save several pieces of information about specific inflammation in a body. This immunological memory named “engrams”, also called memory traces, could restore the initial disease state, which may help to explain key features of schizophrenia. Based on this concept, therapeutic strategies for schizophrenia could be the modification of the gut microbiota. Probiotics and/or fecal microbiota transplantation are now emerging as the most promising treatments for the modification. More consideration of the roles of gut microbiota will conduct the further development of immune-based therapeutics for the prevention and/or treatments of psychiatric disorders.

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Gut microbiota could modulate the effects of neuro-immune responses and memory traces via the gut-brain-immune axis in schizophrenia

Background and aim Excessive intake of sugars and energy from drinks has been postulated to increase the risk of obesity, which may in turn be associated with mental health disorders. In addition, excessive intakes of alcohol and caffeine may co-occur with psychiatric disorders. The purpose of the present pilot study was to estimate energy, sugar, caffeine, and alcohol intakes through the consumption of drinks in patients with schizophrenia and affective disorders and assess potential differences in drink consumption between the two disorders. Methodology The current study included 89 outpatients with schizophrenia (n = 36) and affective disorders (n = 53) attending the psychiatric clinic of the University General Hospital of Larissa (UGHL) in Greece. In addition to anthropometric measurements, the patients were asked to complete a specific, previously validated questionnaire on the frequency of drink consumption in order to estimate sugar, caffeine, and alcohol intakes. Results The participants had a mean body mass index (BMI) of 28.9 ± 5.6 kg/m2 without significant differences between the two types of mental disorders. Similarly, the mean waist circumference (102.6 ± 15.7 cm) and mean body fat percentage (32.9% ± 10.8%) were above the recommended values. The total energy intake from drinks was more than a third of the estimated daily energy requirements. Although there was no significant difference in the mean daily caffeine intake, those with affective disorders had a significantly higher intake of sugars from drinks (median (Mdn) = 80.0 (interquartile range (IQR) = 89.8) g/day) and alcohol (Mdn = 45.6 (IQR = 31.1) g/day), compared to those with schizophrenia (Mdn = 60.0 (IQR = 45.4) g/day and Mdn = 24.9 (IQR = 19.8) g/day, respectively). Conclusions Considering the link between high sugar and alcohol intake with excess body weight and mental health, these preliminary data are of particular concern and point to the need for better dietary counseling in order to improve the dietary behaviors of these patients.

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Sugars, Alcohol, and Caffeine Intake From Drinks Among Outpatients With Mental Health Disorders in Greece: A Pilot Study

Recently, morphological impairments have been detected in the brain of a triple-hit rat schizophrenia model (Wisket), and delayed depressive effects of caffeine treatment in both control and Wisket animals have also been shown. The aims of this study were to determine the basal and caffeine-induced acute (30 min) and delayed (24 h) changes in the cerebral 18fluorodeoxyglucose (18F-FDG) uptake by positron emission tomography (PET) in control and Wisket rats. No significant differences were identified in the basal whole-brain metabolism between the two groups, and the metabolism was not modified acutely by a single intraperitoneal caffeine (20 mg/kg) injection in either group. However, one day after caffeine administration, significantly enhanced 18F-FDG uptake was detected in the whole brain and the investigated areas (hippocampus, striatum, thalamus, and hypothalamus) in the control group. Although the Wisket animals showed only moderate enhancements in the 18F-FDG uptake, significantly lower brain metabolism was observed in this group than in the caffeine-treated control group. This study highlights that the basal brain metabolism of Wisket animals was similar to control rats, and that was not influenced acutely by single caffeine treatment at the whole-brain level. Nevertheless, the distinct delayed responsiveness to this psychostimulant in Wisket model rats suggests impaired control of the cerebral metabolism.

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Caffeine-Induced Acute and Delayed Responses in Cerebral Metabolism of Control and Schizophrenia-like Wisket Rats

Accumulating evidence reported the associations of coffee consumption with physical conditions and mortality, but the associations with mental disorders were limited. The objective of this study was to examine the associations of coffee consumption with incident depression and anxiety, and to assess whether the associations differed by coffee subtypes (instant, ground, and decaffeinated coffee) or additives (milk, sugar-sweetened, and artificial-sweetened). In this prospective cohort study, we utilized data from the UK Biobank and included a total of 146,566 participants who completed the touchscreen questionnaire at baseline between 2006 and 2010. During the follow-up, incident depression and anxiety were measured in 2016 using the Patient Health Questionnaire (PHQ)-9 and the Generalised Anxiety Disorder Assessment (GAD)-7, respectively. Multivariable-adjusted logistic regression models and restricted cubic splines were used to assess the associations. Approximately 80.7% of participants reported consuming coffee, and most drank 2 to 3 cups per day (41.2%). We found J-shaped associations between coffee consumption and both incident depression and anxiety, with the lowest risk of the mental disorders occurring at around 2-3 cups per day. Results were similar for participants who drank 2-3 cups of ground coffee, milk-coffee, or unsweetened coffee. Our findings highlight that 2-3 cups of coffee consumption could be recommended as part of a healthy lifestyle to improve mental health. 

The association between coffee consumption and risk of incident depression and anxiety: Exploring the benefits of moderate intake

Caffeine is the most consumed substance in the world. It is well known to affect alertness and interfere with sleep. Caffeine acts as an adenosine antagonist and indirectly affects other neurotransmitters. DSM-V lists four disorders directly related to caffeine intake. Caffeine interferes with anxiety and sleep disorder. Studies have shown positive effect of caffeine on neurocognitive function, such as Alzheimer’s and Parkinson’s disease. Caffeine is found to improve some elements of depressive disorder, such as amotivation symptom, and it is widely used during the electoral convulsive therapy to lower seizure threshold. It can decrease the lithium level, which might precipitate switch to manic or hypomanic episode and bipolar disorder. Further research and randomized control trials are needed to establish the relationship between caffeine and psychiatric effects. 

Lumei Huang

Papers

Caffeine consumption and schizophrenia: A highlight on adenosine receptor-independent mechanisms.