Background: Despite known association of internet addiction with a reduced brain volume and abnormal connectivity, the impact of excessive smartphone use remains unclear. Methods: PubMed, Embase, ClinicalTrial.gov, and Web of Science databases were systematically searched from inception to July 2022 using appropriate keywords for observational studies comparing differences in brain volumes and activations between excessive smartphone users and individuals with regular use by magnetic resonance imaging. Results: Of the 11 eligible studies retrieved from 6993 articles initially screened, seven and six evaluated brain volumes and activations, respectively. The former enrolled 421 participants (165 excessive smartphone users vs. 256 controls), while the latter recruited 276 subjects with 139 excessive smartphone users. The results demonstrated a smaller brain volume in excessive smartphone users compared to the controls (g = −0.55, p < 0.001), especially in subcortical regions (p < 0.001). Besides, the impact was more pronounced in adolescents than in adults (p < 0.001). Regression analysis revealed a significant positive association between impulsivity and volume reduction. Regarding altered activations, the convergences of foci in the declive of the posterior lobe of cerebellum, the lingual gyrus, and the middle frontal gyrus were noted. Conclusions: Our findings demonstrated a potential association of excessive smartphone use with a reduced brain volume and altered activations.

Background: The efficacy of surface electroencephalographic neurofeedback (EEG-NF) for improving attentional performance assessed by laboratory measures in patients with attention-deficit/hyperactivity disorder (ADHD) remains unclear. Methods: Following the PRISMA guidelines, the PubMed, Embase, ClinicalKey, Cochrane CENTRAL, ScienceDirect, Web of Science, and ClinicalTrials.gov databases were systematically searched for randomized controlled trials on the efficacy of surface EEG-NF against ADHD focusing on attentional performance evaluated by laboratory measures from inception to January 2022. Results: Fourteen eligible studies were analyzed. Of the 718 participants involved, 429 diagnosed with ADHD received EEG-NF treatment. Significant improvement in attentional performance in ADHD subjects receiving EEG-NF was noted compared to their comparators (p < 0.01). Besides, there was a significant EEG-NF-associated beneficial effect on sustained attention (Hedges’ g = 0.32, p < 0.01), whereas the impact on selective attention (p = 0.57) and working memory (p = 0.59) was limited. Moreover, protocol including beta wave enhancement was superior to that only focusing on reducing theta/beta ratio or modulation of slow cortical potential. Subgroup analyses showed that three sessions per week of EEG-NF produced the best effect, while the efficacy of surface EEG-NF was much poorer (Hedges’ g = 0.05) when only studies that blinded their participants from knowledge of treatment allocation were included. No significant difference was noted in the improvement of attentional performance 6–12 months after EEG-NF intervention (n = 3, p = 0.42). Conclusions: Our results demonstrated the satisfactory effectiveness of surface EEG-NF for improving sustained attention, especially when beta wave enhancement was included, despite its failure to sustain a long-term effect. Further large-scale trials are warranted to support our findings.

Background: No established pharmacological treatment is available for the core symptoms of autism spectrum disorder (ASD). This study aimed at investigating the efficacy of antidepressants for the core and associated symptoms of ASD. Methods: We searched PubMed, Embase, ClinicalKey, Cochrane CENTRAL, ScienceDirect, Web of Science and ClinicalTrials.gov using the keywords “ASD” and “antidepressants.” We searched from database inception to June 2021 for randomized controlled trials of antidepressant use in patients with ASD. We calculated pooled effect sizes based on a random-effects model. Results: Analysis of 16 studies with 899 participants showed improvements in restricted and repetitive behaviours (effect size = 0.27) and global symptoms (effect size = 1.0) in patients with ASD taking antidepressants versus those taking placebos (p ≤ 0.01). We found no differences between the 2 groups (p ≥ 0.36) in terms of dropout rate (odds ratio [OR] = 1.17) or rate of study discontinuation because of adverse events (OR = 1.05). We also noted improvements in irritability and hyperactivity in the antidepressant group (Hedges g = 0.33 and 0.22, respectively, both p < 0.03). Subgroup analyses showed significant effects of medication type (i.e., clomipramine was better than SSRIs) and age (antidepressants were more effective in adults than in children or adolescents) on both restricted and repetitive behaviours and global improvement (p < 0.05). Meta-regression demonstrated that better therapeutic effects were associated with lower symptom severity and older age. Limitations: The small effect sizes and variations in treatment response that we found warrant further study. Conclusion: Our results supported the effectiveness of antidepressants for global symptoms and symptom subdomains of ASD, with tolerable adverse effects. Low symptom severity and adulthood were associated with better outcomes.

The significance of probability discounting (PD) among individuals with Internet gaming disorder (IGD) remains unclear. Following the PRISMA guidelines, we systematically searched the PubMed, Embase, and ScienceDirect databases for English articles on Internet addiction that included comparison between individuals with and without IGD as well as probabilistic discounting task as the main outcome from January 1970 to July 2020 using the appropriate keyword strings. The primary outcome was the overall difference in rate of PD, while the secondary outcomes included the difference in PD with magnitude of probabilistic reward and response time of the PD task. Effect size (ES) was calculated through dividing the group means (e.g., h value or AUC) by the pooled standard deviations of the two groups. A total of five studies with 300 participants (i.e., IGD group, n = 150, mean age = 20.27 ± 2.68; healthy controls, n = 150, mean age = 20.70 ± 2.81) were analyzed. The IGD group was more willing to take risks in probabilistic gains but performances on probabilistic losses were similar between the two groups. The IGD group also exhibited a shorter response time (Hedge’s g = − 0.51; 95%CI = − 0.87 to − 0.15). Meta-regression demonstrated a positive correlation between maximum reward magnitude and PD rate (p < 0.04). However, significant publication bias was noted among the included studies (Egger’s test, p < 0.01). In conclusion, individuals with IGD seemed more impulsive in making risky decisions, especially when the potential gains were expected. Our findings not only supported the use of PD for assessing individuals with IGD but may also provide new insights into appropriate interventions.

The structural impact of chronic pain on amygdala in chronic pain (CP) patients remains unclear, although major depression and anxiety are known to be associated with its increase and decrease in size, respectively. This study aimed at examining the relationship between emotional stress and amygdala size in CP patients. The effects of mediating and moderating variables were also examined. The PubMed, Embase, and Web of Science databases were searched for English clinical trials from inception to February 2022 using the appropriate keyword strings. We compared the differences in amygdala size assessed with magnetic resonance imaging between CP patients with emotional stress and healthy counterparts. Of the 49 full-text articles identified, 13 studies enrolling 1,551 participants including 738 CP patients with emotional stress and 813 controls were analyzed. Emotional stress evaluated with questionnaires based on Beck depression inventory, Hamilton depression/anxiety scale, state-trait anxiety inventory, and hospital anxiety and depression scale revealed significant differences between CP patients with emotional stress and controls, indicating a subclinical but significant level of emotional stress in CP patients. The results demonstrated an amygdala shrinkage among CP patients with emotional stress compared to the controls, especially the right side (P = .02). Besides, pain from a single body region was more likely to impact the amygdala size compared to diffuse pain (P = .02). Regression analysis revealed no significant association between continuous variables (age, gender, pain duration/intensity) and amygdala size. Our findings demonstrated that emotional stress was associated with a reduced right amygdala size in CP patients.