Neurocognitive Predictors of Clinical Improvement in Selective Serotonin Reuptake Inhibitor-Treated Adolescents with Major Depressive Disorder

The multifaceted effects of fluoxetine treatment on cognitive functions

Fluoxetine, the prototypical selective serotonin reuptake inhibitor (SSRI), is widely used to treat major depressive disorder (MDD) and a variety of other central nervous system conditions, primarily due to its established clinical safety profile. Although its efficacy in treating depression is well-recognized, the impact of fluoxetine on cognitive functions remains inconsistent and elusive. In this review, we first examine the well-substantiated biological mechanisms underlying fluoxetine's antidepressant effects, which include serotonin reuptake inhibition and activation of TrkB receptors-key to brain-derived neurotrophic factor (BDNF) signaling. Subsequently, we delve into the cognitive side effects observed in both preclinical and clinical studies, affecting domains such as memory, attention, and executive functions. While certain studies indicate cognitive improvements in patients with underlying disorders, there is also evidence of negative effects, influenced by variables like gender, duration of treatment, age, disease pathology, and the specifics of cognitive testing. Significantly, the negative cognitive outcomes reported in preclinical research often involve healthy, non-diseased animals. This review underscores the necessity for heightened caution in fluoxetine prescription and further investigation into its potentially detrimental cognitive effects, even when used prophylactically.

Cognitive Control Deficits in Depression: A Novel Target to Improve Suboptimal Outcomes in Childhood

Cognitive control deficits are one of three primary endophenotypes in depression, and the enhanced targeting of these deficits in clinical and research work is expected to lead to improved depression outcomes. Cognitive control is a set of self-regulatory processes responsible for goal-oriented behavior that predicts clinical/functional outcomes across the spectrum of brain-based disorders. In depression, cognitive control deficits emerge by the first depressive episode, persist during symptom remission, and worsen over the course of depression. In addition, the presence of these deficits predicts a poor response to evidence-based depression treatments, including psychotherapy and antidepressant medication. This is particularly relevant to childhood depression, as 1%-2% of children are diagnosed with depression, yet there are very limited evidence-based treatment options. Cognitive control deficits may be a previously underaddressed factor contributing to poor outcomes, although there remains a dearth of research examining the topic. The investigators describe the prior literature on cognitive control in depression to argue for the need for increased focus on this endophenotype. They then describe cognitive control-focused clinical and research avenues that would likely lead to improved treatments and outcomes for this historically undertreated aspect of childhood depression.

Irritability and Inattention Not Sad Low Mood Predict Impulsiveness in Children and Adolescents With Major Depressive Disorder and Persistent Depressive Disorder

ABSTRACT

The specific relationships between impulsiveness, inattention, sad, low mood, and irritability have not been systematically examined in young people with major depressive disorder with and without persistent depressive disorder. The relationships are important to clarify because these symptom dimensions may increase suicidal risk in children and adolescents with these depressive disorders. A total of 313 medication-naive young people (aged 6-16 years) with active major depressive disorder (MDD) alone, persistent depressive disorder (DD) alone, and comorbid MDD and DD were identified. "Inattention," "sad/unhappy," and "irritable" mood were identified by parent standardized questionnaire. Standard multiple regression was used to investigate how well inattention, sad/unhappy, and irritable mood predict impulsiveness. Inattention (32% of the variance, increased) and irritable mood (5% of the variance, increased) both made independent significant contributions to impulsiveness, whereas sad/unhappy mood did not. Decreasing irritability via more targeted and comprehensive management approaches may ameliorate impulsiveness in young people with these depressive disorders.

Cognitive mechanisms underlying depressive disorders in ADHD: A systematic review

The risk for major depressive disorder (MDD) is considerably increased in young adults with attention-deficit/hyperactivity disorder (ADHD) but underlying mechanisms are poorly understood. This review explores ADHD-specific neurocognitive impairments as possible underlying mechanisms for ADHD-depression comorbidity. Two systematic literature searches were conducted in EBSCOhost, PubMED, and Cochrane Reviews databases according to PRISMA guidelines. The first search identified 18 meta-analyses of cross-sectional and longitudinal studies on cognitive dysfunctions in MDD across the lifespan. The second search identified six original studies on reaction time variability in MDD. During acute depression, children and adults showed cognitive deficits that overlapped with some of the ADHD-related impairments. Findings from remitted patients, high-risk individuals, and few prospective studies suggest that a subset of these shared impairments, specifically executive dysfunctions (selective attention, verbal fluency, working memory) and long-term memory problems, are candidate pre-existing risk markers of depression. We discuss if and how these specific neurocognitive mechanisms may mediate developmental pathways from ADHD to depression. If replicated by longitudinal studies, these findings may guide future prevention strategies.

Spatial working memory performance in children and adolescents with major depressive disorder and dysthymic disorder

BACKGROUND

Spatial working memory (SWM) is known to be impaired in children with Major depressive disorder (MDD), and, separately, Dysthymic disorder (DD) (DSM V persistent depressive disorder equivalent). Yet, it remains unclear whether MDD or DD is associated with worse SWM impairment, whether DD adds to the SWM impairments evident in MDD and whether these findings are evident in children as well as adolescents with MDD and DD.

METHODS

The association of SWM and its strategy and spatial span components is explored in carefully defined children and adolescents (age 6-16 years) with MDD alone (N = 29), MDD and DD (N = 130), DD alone (N = 154) compared to healthy typically developing participants (N = 107), controlling for age, gender, full scale IQ and social adversity status. The relationship between SWM and its strategy and span components and anxious/depressed and inattentive symptoms were also examined.

RESULTS

MDD was associated with worse SWM impairment than DD and there was no evidence of an additive effect of MDD and DD on SWM, strategy and spatial span deficits. Further, these findings were age-independent.

LIMITATIONS

The data presented are cross sectional and limited to SWM deficits in MDD and/or DD.

CONCLUSIONS

This study concurs with and extends current influential models about the cognitive effects of MDD and DD. Clinical implications and future research directions are discussed.