Omega-3 Polyunsaturated Fatty Acids for Core Symptoms of Attention-Deficit/Hyperactivity Disorder: A Meta-Analysis of Randomized Controlled Trials.

Objective: Previous studies have shown conflicting results for the effectiveness of omega-3 polyunsaturated fatty acids (PUFAs) in improving attention-deficit/hyperactivity disorder (ADHD) symptoms. This inconsistency may be due to differences in dosage, composition, and treatment duration. The current meta-analysis aims to address this inconsistency by improving subtype analyses and focusing on heterogeneity in treatment duration, omega-3 PUFA composition, and eicosapentaenoic acid (EPA) dose.Data Sources and Study Selection: We searched PubMed, EMBASE, PsycINFO, and Cochrane Library for randomized controlled trials of omega-3 PUFAs for ADHD, without publication year or language limitations, up to November 27, 2022. The primary outcome was the improvement of ADHD core symptoms. Subgroup analyses were conducted based on the formula, dosages, and composition ratios of omega-3 PUFAs. To ensure methodological quality, the Cochrane Risk-of-Bias Tool 1.0 was utilized to assess the risk of bias for each study included in the analysis. The pooled data were then analyzed using the random-effect meta-analysis, and the inverse variance method was employed.Data Extraction: The outcomes of interest were extracted using a data extraction form developed for this study.Results: Twenty-two studies with 1,789 participants were included in the analysis. Overall, omega-3 PUFAs did not significantly improve ADHD core symptoms compared to placebo (standardized mean difference [SMD]: -0.16; 95% CI, -0.34 to 0.01; P = .07). However, in the subgroup of studies with a treatment duration of at least 4 months, omega-3 PUFAs were significantly more effective than placebo (SMD: -0.35; 95% CI,-0.61 to -0.09; P = .007). Neither high eicosapentaenoic acid (EPA) dosage nor high EPA/docosahexaenoic acid (DHA) ratio was found to improve ADHD symptoms.Conclusions: Our findings indicate that omega-3 PUFAs did not improve ADHD core symptoms, but long-term supplementation may have potential benefits. The main limitation of the study was the moderate heterogeneity and small sample sizes in subgroup analyses and the lack of dietary pattern information.

Brain Mechanisms of Pain and Dysautonomia in Diabetic Neuropathy: Connectivity Changes in Thalamus and Hypothalamus.

CONTEXT: About one-third of diabetic patients suffer from neuropathic pain, which is poorly responsive to analgesic therapy and associated with greater autonomic dysfunction. Previous research on diabetic neuropathy mainly links pain and autonomic dysfunction to peripheral nerve degeneration resulting from systemic metabolic disturbances, but maladaptive plasticity in the central pain and autonomic systems following peripheral nerve injury has been relatively ignored. OBJECTIVE: This study aimed to investigate how the brain is affected in painful diabetic neuropathy (PDN), in terms of altered structural connectivity (SC) of the thalamus and hypothalamus that are key regions modulating nociceptive and autonomic responses. METHODS: We recruited 25 PDN and 13 painless (PLDN) diabetic neuropathy patients, and 27 healthy adults as controls. The SC of the thalamus and hypothalamus with limbic regions mediating nociceptive and autonomic responses was assessed using diffusion tractography. RESULTS: The PDN patients had significantly lower thalamic and hypothalamic SC of the right amygdala compared with the PLDN and control groups. In addition, lower thalamic SC of the insula was associated with more severe peripheral nerve degeneration, and lower hypothalamic SC of the anterior cingulate cortex was associated with greater autonomic dysfunction manifested by decreased heart rate variability. CONCLUSION: Our findings indicate that alterations in brain structural connectivity could be a form of maladaptive plasticity after peripheral nerve injury, and also demonstrate a pathophysiological association between disconnection of the limbic circuitry and pain and autonomic dysfunction in diabetes.

Brain imaging signature of neuropathic pain phenotypes in small-fiber neuropathy: altered thalamic connectome and its associations with skin nerve degeneration.

ABSTRACT: Small-fiber neuropathy (SFN) has been traditionally considered as a pure disorder of the peripheral nervous system, characterized by neuropathic pain and degeneration of small-diameter nerve fibers in the skin. Previous functional magnetic resonance imaging studies revealed abnormal activations of pain networks, but the structural basis underlying such maladaptive functional alterations remains elusive. We applied diffusion tensor imaging to explore the influences of SFN on brain microstructures. Forty-one patients with pathology-proven SFN with reduced skin innervation were recruited. White matter connectivity with the thalamus as the seed was assessed using probabilistic tractography of diffusion tensor imaging. Patients with SFN had reduced thalamic connectivity with the insular cortex and the sensorimotor areas, including the postcentral and precentral gyri. Furthermore, the degree of skin nerve degeneration, measured by intraepidermal nerve fiber density, was associated with the reduction of connectivity between the thalamus and pain-related areas according to different neuropathic pain phenotypes, specifically, the frontal, cingulate, motor, and limbic areas for burning, electrical shocks, tingling, mechanical allodynia, and numbness. Despite altered white matter connectivity, there was no change in white matter integrity assessed with fractional anisotropy. Our findings indicate that alterations in structural connectivity may serve as a biomarker of maladaptive brain plasticity that contributes to neuropathic pain after peripheral nerve degeneration.