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Major Depressive Disorder (MDD) is a prevalent, chronic, disabling, and multidimensional mental disorder. Cognitive dysfunction represents a core diagnostic and symptomatic criterion of MDD, and is a principal determinant of functional non-recovery. Cognitive impairment has been observed to persist despite remission of mood symptoms, suggesting dissociability of mood and cognitive symptoms in MDD. Recurrent impairments in several domains including, but not limited to, executive function, learning and memory, processing speed, and attention and concentration, are associated with poor psychosocial and occupational outcomes. Attempts to restore premorbid functioning in individuals with MDD requires regular screenings and assessment of objective and subjective measures of cognition by clinicians. Easily accessible and cost-effective tools such as the THINC-integrated tool (THINC-it) are suitable for use in a busy clinical environment and appear to be promising for routine usage in clinical settings. However, antidepressant treatments targeting specific cognitive domains in MDD have been insufficiently studied. While select antidepressants, e.g., vortioxetine, have been demonstrated to have direct and independent pro-cognitive effects in adults with MDD, research on additional agents remains nascent. A comprehensive clinical approach to cognitive impairments in MDD is required. The current narrative review aims to delineate the importance and relevance of cognitive dysfunction as a symptomatic target for prevention and treatment in the phenomenology of MDD.

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Cognitive dysfunction is a symptomatic domain identified across many mental disorders. Cognitive deficits in individuals with major depressive disorder (MDD) contribute significantly to occupational and functional disability. Notably, cognitive subdomains such as learning and memory, executive functioning, processing speed, and attention and concentration are significantly impaired during, and between, episodes in individuals with MDD. Most antidepressants have not been developed and/or evaluated for their ability to directly and independently ameliorate cognitive deficits. Multiple interacting neurobiological mechanisms (eg, neuroinflammation) are implicated as subserving cognitive deficits in MDD. A testable hypothesis, with preliminary support, posits that improving performance across cognitive domains in individuals with MDD may improve psychosocial function, workplace function, quality of life, and other patient-reported outcomes, independent of effects on core mood symptoms. Herein we aim to (1) provide a rationale for prioritizing cognitive deficits as a therapeutic target, (2) briefly discuss the neurobiological substrates subserving cognitive dysfunction, and (3) provide an update on current and future treatment avenues.

Objectives: Extant evidence indicates that ketamine exerts rapid antidepressant effects in treatment-resistant depressive (TRD) symptoms as a part of major depressive disorder (MDD) and bipolar disorder (BD). The identification of depressed sub-populations that are more likely to benefit from ketamine treatment remains a priority. In keeping with this view, the present narrative review aims to identify the pretreatment predictors of response to ketamine in TRD as part of MDD and BD. Method: Electronic search engines PubMed/MEDLINE, , and Scopus were searched for relevant articles from inception to January 2018. The search term ketamine was cross-referenced with the terms depression, major depressive disorder, bipolar disorder, predictors, and response and/or remission. Results: Multiple baseline pretreatment predictors of response were identified, including clinical (i.e., Body Mass Index (BMI), history of suicide, family history of alcohol use disorder), peripheral biochemistry (i.e., adiponectin levels, vitamin B12 levels), polysomnography (abnormalities in delta sleep ratio), neurochemistry (i.e., glutamine/glutamate ratio), neuroimaging (i.e., anterior cingulate cortex activity), genetic variation (i.e., Val66Met BDNF allele), and cognitive functioning (i.e., processing speed). High BMI and a positive family history of alcohol use disorder were the most replicated predictors. Conclusions: A pheno-biotype of depression more, or less likely, to benefit with ketamine treatment is far from complete. Notwithstanding, metabolic-inflammatory alterations are emerging as possible pretreatment response predictors of depressive symptom improvement, most notably being cognitive impairment. Sophisticated data-driven computational methods that are iterative and agnostic are more likely to provide actionable baseline pretreatment predictive information.

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To determine, via narrative, non-systematic review of pre-clinical and clinical studies, whether the effect of cannabis on hepatic biotransformation pathways would be predicted to result in clinically significant drug-drug interactions (DDIs) with commonly prescribed psychotropic agents. Areas covered: A non-systematic literature search was conducted using the following databases: PubMed, PsycInfo, and Scopus from inception to January 2017. The search term cannabis was cross-referenced with the terms drug interactions, cytochrome, cannabinoids, cannabidiol, and medical marijuana. Pharmacological, molecular, and physiologic studies evaluating the pharmacokinetics of Δ-tetrahydrocannabinol (Δ-THC) and cannabidiol (CBD), both in vitro and in vivo, were included. Bibliographies were also manually searched for additional citations that were relevant to the overarching aim of this paper. Expert opinion: Δ-Tetrahydrocannabinol and CBD are substrates and inhibitors of cytochrome P450 enzymatic pathways relevant to the biotransformation of commonly prescribed psychotropic agents. The high frequency and increasing use of cannabis invites the need for healthcare providers to familiarize themselves with potential DDIs in persons receiving select psychotropic agents, and additionally consuming medical marijuana and/or recreational marijuana.

Convergent evidence demonstrates that immune dysfunction (e.g. chronic low-grade inflammatory activation) plays an important role in the development and progression of mood disorders. The Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway is a pleiotropic cellular cascade that transduces numerous signals, including signals from the release of cytokines and growth factors. The JAK/STAT signaling pathway is involved in mediating several functions of the central nervous system, including neurogenesis, synaptic plasticity, gliogenesis, and microglial activation, all of which have been implicated in the pathophysiology of mood disorders. In addition, the antidepressant actions of current treatments have been shown to be mediated by JAK/STAT-dependent mechanisms. To date, two JAK inhibitors (JAKinibs) have been approved by the U.S. Food and Drug Administration and are primarily indicated for the treatment of inflammatory conditions such as rheumatoid arthritis. Indirect evidence from studies in populations with inflammatory conditions indicates that JAKinibs significantly improve measures of mood and quality of life. There is also direct evidence from studies in populations with depressive disorders, suggesting that JAK/STAT pathways may be involved in the pathophysiology of depression and that the inhibition of specific JAK/STAT pathways (i.e. via JAKinibs) may be a promising novel treatment for depressive disorders.