Effort-based decision-making is affected by overweight/obesity in major depressive disorder

Glucagon-like peptide 1 agonist and effects on reward behaviour: A systematic review

INTRODUCTION

The roles of metabolic signals, including Glucagon-like peptide 1 (GLP-1), have been implicated in multiple domains outside metabolic regulation. There is a growing interest in repurposing Glucagon-like peptide 1 receptor agonists (GLP-1RAs) as therapeutics for motivation and reward-related behavioural disturbances. Herein, we aim to systematically review the extant evidence on the potential effects of GLP-1RAs on the reward system.

METHODS

The study followed PRISMA guidelines using databases such as OVID, PubMed, Scopus, and Google Scholar. The search focused on "Reward Behavior" and "Glucagon Like Peptide 1 Receptor Agonists" and was restricted to human studies. Quality assessment achieved by the NIH's Quality Assessment of Controlled Intervention Studies RESULTS: GLP-1RAs consistently reduced energy intake and influenced reward-related behaviour. These agents have been associated with decreased neurocortical activation in response to higher rewards and food cues, particularly high-calorie foods, and lowered caloric intake and hunger levels.

DISCUSSION

GLP-1RAs show promise in addressing reward dysfunction linked to food stimuli, obesity, and T2DM. They normalize insulin resistance, and might also modulate dopaminergic signalling and reduce anhedonia. Their effects on glycemic variability and cravings suggest potential applications in addiction disorders.

Neurobiological foundations and clinical relevance of effort-based decision-making

Applying effort-based decision-making tasks provides insights into specific variables influencing choice behaviors. The current review summarizes the structural and functional neuroanatomy of effort-based decision-making. Across 39 examined studies, the review highlights the ventromedial prefrontal cortex in forming reward-based predictions, the ventral striatum encoding expected subjective values driven by reward size, the dorsal anterior cingulate cortex for monitoring choices to maximize rewards, and specific motor areas preparing for effort expenditure. Neuromodulation techniques, along with shifting environmental and internal states, are promising novel treatment interventions for altering neural alterations underlying decision-making. Our review further articulates the translational promise of this construct into the development, maintenance and treatment of psychiatric conditions, particularly those characterized by reward-, effort- and valuation-related deficits.

Adjunctive cariprazine for major depressive disorder: a systematic review and meta-analysis

Converging evidence has suggested that treatment augmentation with a second-generation atypical antipsychotic (SGA) may improve treatment outcomes in major depressive disorder (MDD) patients after an incomplete response to a first-line antidepressant. Cariprazine is a recently approved SGA for MDD augmentation. Herein, we evaluate both continuous (ie, change in depressive symptom severity scores over time) and categorical (ie, remission and response rates) outcomes. Following a full-text review, four randomized controlled trials (RCTs) were included in our meta-analysis, while five studies were included for a qualitative review. Risk ratios (RRs) were calculated for all included randomized controlled studies to determine the relative response and remission rates of cariprazine compared to placebo augmentation. The RR for all-cause dropout was also determined as a proxy for overall acceptability. Two studies found a statistically significant treatment response using cariprazine augmentation. One study observed depressive symptom remission for cariprazine compared to placebo. Our random-effects model revealed moderate antidepressant effects of cariprazine, with a standardized mean difference (SMD) in Montgomery-Åsberg Depression Rating Scale (MADRS) scores of -1.79 (95% CI): -2.89, -0.69). Our pooled response RR and remission RR were calculated as 1.21 (95% CI: 1.05, 1.39, P=0.008) and 0.99 (95% CI: 0.84, 1.17, P=0.91), respectively. The RR for response was statistically significant (P<0.05). However, the RR for remission was not statistically significant. The findings from our meta-analysis include a variable magnitude of effects. Evidence suggests cariprazine may be an effective treatment for MDD; however, further results are needed to clarify this relation.

Impact of Elevated Body Mass Index (BMI) on Hedonic Tone in Persons with Post-COVID-19 Condition: A Secondary Analysis

INTRODUCTION

The post-COVID-19 condition (PCC) is characterized by persistent, distressing symptoms following an acute COVID-19 infection. These symptoms encompass various domains, including hedonic tone, which is critical for overall well-being. Furthermore, obesity is both a risk factor for COVID-19 and PCC and associated with impaired hedonic tone. This study aims to investigate whether elevated body mass index (BMI) is associated with hedonic tone in persons with PCC.

METHODS

We perform a post hoc analysis of a randomized, double-blind, placebo-controlled clinical trial investigating the impact of vortioxetine on cognitive impairment in persons with PCC. Statistical analysis of baseline data using a generalized linear model was undertaken to determine the relationship of BMI to hedonic tone measured by Snaith-Hamilton Pleasure Scale (SHAPS) scores. The model was adjusted for covariates including age, sex, race, suspected versus confirmed COVID-19 cases, alcohol amount consumed per week, and annual household income.

RESULTS

The baseline data of 147 participants were available for analysis. BMI had a statistically significant positive association with baseline SHAPS total scores (β = 0.003, 95% CI [6.251E-5, 0.006], p = 0.045), indicating elevated BMI is associated with deficits in self-reported reward system functioning.

CONCLUSION

Higher BMI is associated with greater deficits in hedonic tone in persons with PCC, which may impact reward functioning processes such as reward prediction and processing. The mediatory effect of BMI on reward function underscores the need to investigate the neurobiologic interactions to elucidate preventative and therapeutic interventions for persons with PCC. Therapeutic development targeting debilitating features of PCC (e.g., motivation, cognitive dysfunction) could consider stratification on the basis of baseline BMI.

TRIAL REGISTRATION NUMBER

NCT05047952.

Overweight or Obesity Rate and Risk Factors in First-Episode and Drug-Naïve Patients with Major Depressive Disorder with Comorbid Abnormal Lipid Metabolism: A Large-Scale Cross-Sectional Study

Overweight and obesity are frequent symptoms in patients with major depressive disorder (MDD) and abnormal lipid metabolism (ALM). There are no studies on the rate, risk factors, and underlying mechanisms of overweight/obesity in Chinese patients with MDD with comorbid ALM. The purpose of this study was to examine the rate of overweight/obesity and the associated risk factors among Chinese patients with MDD first-episode and drug-naïve (FEDN) with comorbid ALM. This study was a cross-sectional research work. A total of 1718 patients were enrolled. Their clinical and laboratory data were obtained. All participants were assessed with the 17-item Hamilton Depression Rating Scale (HAMD), the Hamilton Anxiety Rating Scale (HAMA), and the Positive and Negative Syndrome Scale (PANSS) positive subscale. The plasma total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triacylglycerols (TG), blood glucose concentrations, thyroid peroxidase antibody (A-TPO), thyoglubulin antibody (A-TG), thyroid-stimulating hormone (TSH), free thyoxine (FT4) and free triiodothyronine (FT3), and blood glucose concentrations were measured. ALM was identified as elevations in the plasma lipid values in this study. Of all the included subjects, the rate of ALM was 81.1%. The rate of obesity and overweight was 3.94% and 57.21%, respectively. Logistic regression analysis showed that TSH was the independent risk factor for overweight or obesity in MDD patients (adjusted OR = 1.158, 95%CI = 1.081-1.24, p < 0.001). The risk of developing overweight or obesity in MDD with ALM with comorbid TSH abnormalities was 2.176 times higher than those without TSH abnormalities (p < 0.001). Further linear regression showed TSH level (B = 0.1, t = 3.376, p = 0.001) and systolic blood pressure (B = 0.015, t = 2.351, p = 0.019) were risk factors for a higher body mass index (BMI). Our results demonstrate that being overweight is very frequent among patients with FEDN MDD with comorbid ALM but not obesity. TSH was the risk factor for overweight and obesity in MDD patients with comorbid ALM.

Impact of insulin and insulin resistance on brain dopamine signalling and reward processing- an underexplored mechanism in the pathophysiology of depression?

Type 2 diabetes and major depressive disorder (MDD) are the leading causes of disability worldwide and have a high comorbidity rate with fatal outcomes. Despite the long-established association between these conditions, the underlying molecular mechanisms remain unknown. Since the discovery of insulin receptors in the brain and the brain's reward system, evidence has accumulated indicating that insulin modulates dopaminergic (DA) signalling and reward behaviour. Here, we review the evidence from rodent and human studies, that insulin resistance directly alters central DA pathways, which may result in motivational deficits and depressive symptoms. Specifically, we first elaborate on the differential effects of insulin on DA signalling in the ventral tegmental area (VTA) - the primary DA source region in the midbrain - and the striatum as well as its effects on behaviour. We then focus on the alterations induced by insulin deficiency and resistance. Finally, we review the impact of insulin resistance in DA pathways in promoting depressive symptoms and anhedonia on a molecular and epidemiological level and discuss its relevance for stratified treatment strategies.

Evaluating the neural substrates of effort-expenditure for reward in adults with major depressive disorder and obesity

Converging evidence has suggested that disturbances in monetary reward processing may subserve the shared biosignature between major depressive disorder (MDD) and obesity. However, there remains a paucity of studies that have evaluated the deficits in specific subcomponents of reward functioning in populations with MDD and obesity comorbidity. We evaluated the association between effort-expenditure for monetary reward and neural activation in regions associated with reward-based decision making (i.e., the caudate nucleus, anterior cingulate cortex (ACC) and hippocampus) in people with MDD and obesity comorbidity. We acquired structural and functional magnetic resonance imaging (fMRI) in 12 participants and performed a spherical region-of-interest analysis (ROI) using previously defined peak MNI coordinates. A one-sample t-test was employed to compare ROI-specific blood-oxygen-level-dependent (BOLD) signal change during the task choice selection window (i.e., high-effort vs. low-effort task) of the effort-expenditure for reward task (EEfRT). We observed no change in activation of the caudate nucleus, ACC or hippocampus in participants with increased BMI when contrasting the high effort > low effort reward magnitude condition for the EEfRT. The findings from our exploratory study evaluated the disturbances in fundamental reward processes, including cost-benefit decision making, in people MDD and obesity. Future studies should further investigate this relationship with a larger sample size.

The Relationship between Social Anhedonia and Perceived Pleasure from Food-An Exploratory Investigation on a Consumer Segment with Depression and Anxiety

Anhedonia, the diminished ability to experience pleasure, is a key symptom of a range of mental and neurobiological disorders and is associated with altered eating behavior. This research study investigated the concept of anhedonia in relation to mental disorders and the perception of pleasure from food to better understand the link between anhedonia and eating behavior. A consumer survey (n = 1051), including the Food Pleasure Scale, the Chapman Revised Social Anhedonia Scale, the Patient Health Questionnaire, and the Generalized Anxiety Disorder scale, was conducted to explore the perception of pleasure from food among people with anhedonic traits. Comparative analyses were performed between people with symptoms of depression and/or anxiety and people with no symptoms of these conditions. A segmentation analysis was furthermore performed based on three levels of anhedonia: Low, Intermediate and High anhedonia. Thus, insights into how food choice and eating habits may be affected by different levels of anhedonia are provided for the first time. Our findings showed that the 'Low anhedonia' segment found pleasure in all aspects of food pleasure, except for the aspect 'eating alone'. 'Eating alone' was, however, appreciated by the 'Intermediate anhedonia' and 'High anhedonia' segments. Both the 'Intermediate anhedonia' and 'High anhedonia' segments proved that their perceptions of food pleasure in general were affected by anhedonia, wherein the more complex aspects in particular, such as 'product information' and 'physical sensation', proved to be unrelated to food pleasure. For the 'High anhedonia' segment, the sensory modalities of food were also negatively associated with food pleasure, indicating that at this level of anhedonia the food itself is causing aversive sensations and expectations. Thus, valuable insights into the food pleasure profiles of people with different levels of anhedonia have been found for future research in the fields of mental illness, (food) anhedonia, and consumer behaviors.

Characterizing eating behavioral phenotypes in mood disorders: a narrative review

Mood disorders, including depressive and bipolar disorders, represent a multidimensional and prevalent group of psychiatric illnesses characterized by disturbances in emotion, cognition and metabolism. Maladaptive eating behaviors in mood disorders are diverse and warrant characterization in order to increase the precision of diagnostic criteria, identify subtypes and improve treatment strategies. The current narrative review synthesizes evidence for Eating Behavioral Phenotypes (EBP) in mood disorders as well as advancements in pathophysiological conceptual frameworks relevant to each phenotype. Phenotypes include maladaptive eating behaviors related to appetite, emotion, reward, impulsivity, diet style and circadian rhythm disruption. Potential treatment strategies for each phenotype are also discussed, including psychotherapeutic, pharmacological and nutritional interventions. Maladaptive eating behaviors related to mood disorders are relevant from both clinical and research perspectives, yet have been somewhat overlooked thus far. A better understanding of this aspect of mood disorders holds promise to improve clinical care in this patient group and contribute to the subtyping of these currently subjectively diagnosed and treated disorders.

The association between overweight/obesity and poor cognitive function is mediated by inflammation in patients with major depressive disorder

BACKGROUND

Cognitive dysfunction is a common and core feature of major depressive disorder (MDD). Evidences exerted a potentially harmful role of obesity and higher peripheral levels of inflammation in cognitive function, but few studies have explored whether markers of peripheral inflammation might mediate the association between overweight/obesity and deficits in cognitive function. Our study aimed to examine the cognitive function in MDD patients and clarify the effects of overweight/obesity and inflammatory cytokines on cognitive dysfunction in this population.

METHOD

We used a cross-sectional design in this study. A total of 265 patients with MDD were enrolled and divided into underweight, normal weight and overweight/obese groups. The MATRICS Consensus Cognitive Battery (MCCB) was administered to measure the cognition. Plasma levels of nineteen cytokines were measured using high sensitivity multiplex bead-based assays.

RESULTS

We found overweight/obese MDD patients associated with higher plasma levels of tumor necrosis factor (TNF)-α, interleukin (IL)-8, and macrophage inflammatory protein (MIP)-1β and worse performance in speed of processing and working memory. The mediation analysis found higher levels of IL-8 (direct: β = -0.591 (95 % Confidence Interval (CI): -1.0 to -0.2), P = 0.002; indirect: β = 0.060 (95 % CI.: 0.0-0.2), P = 0.032) and TNF-α (direct: β = -0.589 (95 % CI.: -1.0 to -0.2), P = 0.002; indirect: β = 0.059 (95 % CI.: 0.1-0.2), P = 0.037) were associated with more deficits in speed of processing, and partially mediated the relationship between body mass index and speed of processing.

CONCLUSION

Our results suggest that elevated inflammation might be one biological mechanism underlying the link between higher body mass and deficits in processing speed in patients with MDD.

Frequency analysis of symptomatic worsening following ketamine infusions for treatment resistant depression in a real-world sample: Results from the canadian rapid treatment center of excellence

Antidepressants are associated with symptomatic worsening in a subgroup of patients. Replicated evidence has demonstrated rapid and robust antidepressant effects with intravenous (IV) ketamine in treatment resistant depression (TRD); however, the risk of ketamine worsening depressive symptoms in a subgroup of patients remains unknown. Herein we report a retrospective analysis on the rates of symptomatic worsening during an acute course of IV ketamine in individuals with unipolar (n = 142) and bipolar (n = 22) TRD. Adults (N = 164; mean age = 45.97) with TRD underwent four sub-anesthetic infusions (0.5-0.75 mg/kg over 40 min) of IV ketamine over two weeks, and were assessed with the Quick Inventory for Depression Symptomatology-Self Report-16 (QIDS-SR₁₆) at baseline and after each infusion. The primary outcome was the proportion of patients experiencing clinically significant worsening of depressive symptoms (≥20% increase on the QIDS-SR₁₆) at each time point relative to baseline. Secondary analyses explored trends in the results. The frequency of clinically significant worsening fluctuated between 1.83% to 5.49%, with no identifiable trend across time. Zero individuals with bipolar TRD reported symptomatic worsening. Limitations include the single-centered, uncontrolled, retrospective nature of this study. Rates of symptomatic worsening associated with IV ketamine therapy for TRD appear to be very low and similar to conventional antidepressants.

Role of obesity in systemic low-grade inflammation and cognitive function in patients with bipolar I disorder or major depressive disorder

BACKGROUND

Studies have suggested the detrimental effects of obesity and systemic inflammation on the cognitive function of patients with bipolar or major depressive disorder. However, the complex associations between affective disorder, obesity, systemic inflammation, and cognitive dysfunction remain unclear.

METHODS

Overall, 110 patients with affective disorder (59 with bipolar I disorder and 51 with major depressive disorder) who scored ≥61 on the Global Assessment of Functioning and 51 age- and sex-matched controls were enrolled. Body mass index ≥25 kg/m2 was defined as obesity or overweight. Levels of proinflammatory cytokines-including interleukin-6, tumor necrosis factor (TNF)-α, and C-reactive protein (CRP)-were measured, and cognitive function was assessed using various methods, including the Wisconsin Card Sorting Test (WCST) and go/no-go task.

RESULTS

Patients with bipolar I disorder or major depressive disorder were more likely to be obese or overweight, had higher CRP and TNF-α levels, and had greater executive dysfunction in the WCST than the controls. TNF-α level (P < .05) but not affective disorder diagnosis or obesity/overweight was significantly associated with cognitive function deficits, although obesity/overweight and diagnosis were significantly associated with increased TNF-α level.

CONCLUSIONS

Our findings may indicate that proinflammatory cytokines, but not obesity or overweight, have crucial effects on cognitive function in patients with bipolar I disorder or major depressive disorder, although proinflammatory cytokines and obesity or overweight were found to be strongly associated. The complex relationships between affective disorder diagnosis, proinflammatory cytokine levels, obesity or overweight, and cognitive function require further investigation.

Psychiatric Safety and Weight Loss Efficacy of Naltrexone/bupropion as Add-on to Antidepressant Therapy in Patients with Obesity or Overweight

There is significant association between obesity and depression. Naltrexone/Bupropion (NB) is indicated for treatment of overweight and obesity (BMI ≥27 kg/m² with a comorbidity or ≥30 kg/m²). This post-hoc analysis examines safety and efficacy of NB and placebo among individuals with overweight or obesity who were also taking antidepressant therapy during the LIGHT trial (N=8910). Subjects were divided into four subgroups: NB + antidepressants (n=1150), NB without antidepressants (n=3300), placebo + antidepressants (n=1127) and placebo without antidepressants (n=3317). Among subjects taking NB, the combined incidence of serious adverse events (AEs) and AEs leading to treatment discontinuation was not significantly different between those on antidepressants and those who were not. The key weight-loss efficacy analyses were performed on NB or placebo-treated subjects who remained on study therapy through 104 weeks and who did or did not have documented antidepressant use at each of the baseline, week 52 and week 104 visits (Completers: N=1811; 47.0% female, 86.9% white, mean age of 61 years, mean baseline BMI 37.4 kg/m²). The mean adjusted weight change in subjects taking antidepressants was numerically, but not significantly greater for NB vs. placebo (-6.3% vs. -4.3%). For those subjects not on antidepressants, weight loss was significantly greater for NB vs. PL (-6.8% vs. -3.6%). NB is generally well tolerated in patients with overweight or obesity who are on antidepressants and is effective in promoting weight loss regardless of antidepressant use. These results show that for patients on antidepressant therapy, NB may be an effective option for obesity management.

Is Obesity A Determinant Of Success With Pharmacological Treatment For Depression? A Systematic Review, Meta-Analysis And Meta-Regression

BACKGROUND

The bidirectional association between Major Depressive Disorder (MDD) and obesity suggests that body mass index (BMI) at the baseline could influence remission rates (RR) with pharmacological treatment. We evaluated the influence of baseline BMI on the chances of remission among patients with MDD administered antidepressants.

METHODS

Based on the guidelines of the PRISMA statement, we conducted a systematic review on PubMed, Cochrane and Embase databases with subsequent meta-analysis and meta-regression. We included only randomized controlled trials evaluating the efficacy of antidepressants of different classes (monotherapy and combined therapies) that evidenced baseline BMI assessment. We created a model to describe the linear relationship between baseline BMI and RR.

RESULTS

Our systematic review yielded 70 studies with a total of 9,779 patients in the active group and 7,136 patients in the placebo group. In placebo controlled studies, BMI influenced the RR of patients randomized to active treatment. The RR for antidepressants in monotherapy was higher in normal weight to overweight patients rather than obese patients (33% vs 12%, respectively). Also in monotherapy, the RR is higher when the study is conducted on patients with a lower baseline BMI (p=0.029). For combined therapies, the pooled RR was higher in obese patients rather than in normal weight to overweight patients (75% vs 17%, respectively).

LIMITATIONS

BMI provides no information about body composition and obesity can be related to several potential confounders that potentially influence RR.

CONCLUSION

The RR with antidepressant therapy seems to be associated with baseline BMI in patients with MDD, although this simple variable was insufficiently explored so far.

The impact of overweight/obesity on monetary reward processing: A systematic review

OBJECTIVE

Converging evidence suggests abnormalities in monetary reward processing may underlie the shared pathophysiology between major depressive disorder and obesity. As such, there is a need to parse deficits in specific subcomponents of monetary reward functioning (i.e., valuation, learning and anticipation).

METHODS

PsycINFO, Google Scholar and PubMed databases were searched for English-language articles published between database inception to June 6th, 2020. Studies were identified using the following medical search heading (MeSH) terms and search strings: (reward (valuation OR motivation OR anticipation OR learning OR functioning OR decision-making OR reinforcement)) AND ((obesity OR overweight OR obese).

RESULTS

Findings were reviewed from 11 studies evaluating the association between obesity and monetary reward processing. Four studies found significant differences in reward learning in individuals with obesity compared to normal-weight participants. Five studies found body mass index (BMI) to be predictive of willingness to expend effort (i.e., valuation) for a monetary reward. Three studies found changes in neural activations in the ventral striatum during anticipatory phases preceding receipt of a monetary reward in participants with obesity.

CONCLUSIONS

Participants with obesity demonstrated significantly poorer performance in task-based measures of reward learning, valuation, and anticipation, resulting in lower monetary reward outcomes across all studies compared to healthy controls. Notably, participants with obesity and comorbid depression performed worse than participants with no comorbid depression.

LIMITATIONS

There persists heterogeneity between studies with regards to inclusion of mood disorder populations and exclusion of psychiatric comorbidities in groups with obesity.

A novel method for automatic pharmacological evaluation of sucrose preference change in depression mice

Sucrose preference test (SPT) is a most frequently applied method for measuring anhedonia, a core symptom of depression, in rodents. However, the method of SPT still remains problematic mainly due to the primitive, irregular, and inaccurate various types of home-made equipment in laboratories, causing imprecise, inconsistent, and variable results. To overcome this issue, we devised a novel method for automatic detection of anhedonia in mice using an electronic apparatus with its program for automated detecting the behavior of drinking of mice instead of manual weighing the water bottles. In this system, the liquid surface of the bottles was monitored electronically by infrared monitoring elements which were assembled beside the plane of the water surface and the information of times and duration of each drinking was collected to the principal machine. A corresponding computer program was written and installed in a computer connected to the principal machine for outputting and analyzing the data. This new method, based on the automated system, was sensitive, reliable, and adaptable for evaluation of stress- or drug-induced anhedonia, as well as taste preference and effects of addictive drugs. Extensive application of this automated apparatus for SPT would greatly improve and standardize the behavioral assessment method of anhedonia, being instrumental in novel antidepressant screening and depression researching.

Cumulative Cardiovascular Disease Risk and Triglycerides Differentially Relate to Subdomains of Executive Function in Bipolar Disorder; preliminary findings

OBJECTIVES

Cardiovascular disease is disproportionally prevalent in bipolar disorder (BD) and has been linked to cognition in preliminary studies. Herein we evaluate the association between known risk factors for cardiovascular disease and executive function in BD patients compared to healthy controls.

METHODS

In a sample of n=57 individuals (n=23 BD, n=34 controls) we assessed two subdomains of executive function; cognitive flexibility (using the Trail Making Test - Part B) and cognitive inhibition (using the Stroop Colour Word Interference Task). Cardiovascular risk was assessed by means of serum triglyceride levels, body mass index (BMI) and waist circumference, as well as dietary saturated fat intake and a sex-specific cumulative cardiovascular risk score calculated using the Framingham Heart Study method.

RESULTS

Patients with BD had higher BMI and waist circumference, with more BD patients categorized as having central obesity than controls. In the BD group only, higher triglyceride levels were associated with worse cognitive flexibility, and elevated cumulative cardiovascular disease risk was associated with worse cognitive inhibition. No correlations between cardiovascular risk factors and executive function were evident in the control group.

LIMITATIONS

The study was limited by the small sample size and should be considered hypothesis-generating CONCLUSIONS: The associations between triglyceride levels, cumulative cardiovascular disease risk and executive functioning evident in BD in this study preliminarily indicate the potential for mechanistic overlap of physical health and cognitive function in the disorder.

What is bipolar disorder? A disease model of dysregulated energy expenditure

Advances in the understanding and management of bipolar disorder (BD) have been slow to emerge. Despite notable recent developments in neurosciences, our conceptualization of the nature of this mental disorder has not meaningfully progressed. One of the key reasons for this scenario is the continuing lack of a comprehensive disease model. Within the increasing complexity of modern research methods, there is a clear need for an overarching theoretical framework, in which findings are assimilated and predictions are generated. In this review and hypothesis article, we propose such a framework, one in which dysregulated energy expenditure is a primary, sufficient cause for BD. Our proposed model is centered on the disruption of the molecular and cellular network regulating energy production and expenditure, as well its potential secondary adaptations and compensatory mechanisms. We also focus on the putative longitudinal progression of this pathological process, considering its most likely periods for onset, such as critical periods that challenges energy homeostasis (e.g. neurodevelopment, social isolation), and the resulting short and long-term phenotypical manifestations.