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Background: Observational studies that have supported the role of the leptin level in schizophrenia (SCZ) risk are conflicting. Therefore, we performed a two-sample Mendelian randomization (MR) analysis to investigate whether the circulating leptin and soluble plasma leptin receptor (sOB-R) levels play a causal role in SCZ risk.Methods: We first selected five independent single-nucleotide polymorphisms (SNPs) associated with the circulating leptin level and three independent SNPs associated with the sOB-R level from two genome-wide association studies (GWASs) of European individuals. Then, we extracted their associations with SCZ using a large-scale GWAS that consisted of 40,675 patients with SCZ and 64,643 controls of European ancestry. We performed an MR analysis using the inverse variance-weighted (IVW) method to examine the causal effect of leptin on SCZ risk. Moreover, we performed sensitivity analyses to verify our MR results using the weighted median and MR-Egger methods.Results: According to the IVW method, genetically predicted circulating leptin levels were not associated with SCZ risk (OR = 1.98, for per 1-SD unit increase in leptin level; 95% CI, 0.87–4.53; p = 0.10). In addition, the sOB-R level showed no causal effect on the SCZ risk using IVW (OR = 0.98 for per 1-SD unit increase in sOB-R level; 95% CI, 0.97–1.00; p = 0.06). Our sensitivity analysis results confirmed our MR findings.Conclusions: By estimating the causal effect of leptin on SCZ risk using the MR methods, we identified no effect of genetically predicted circulating leptin or the sOB-R level on SCZ. As such, our study suggests that leptin might not be a risk factor for SCZ.

BackgroundHigher homocysteine (Hcy) level has been suggested to be associated with major psychiatric disorders (MPDs), such as schizophrenia (SCZ), bipolar disorder (BD), and major depressive disorder (MDD). We investigated the causal relationships between plasma Hcy level and MPDs risks using the Mendelian randomization (MR) method.MethodsWe selected 18 loci associated with plasma Hcy level from a large-scale genome-wide association study (GWAS) as genetic instruments. Genetic associations with SCZ, MDD, BD and BD subtypes (BD-I and BD-II) were extracted from several GWAS datasets from the Psychiatric Genomics Consortium. We used the Generalized Summary-data-based Mendelian Randomization (GSMR) method to estimate the associations of genetically predicted plasma Hcy levels with MPDs risks. We also performed inverse variance-weighted (IVW) analysis to verify the GSMR results and used MR-Egger regression and leave-one-out analysis to test the assumptions for a valid MR analysis.ResultsGenetically predicted plasma Hcy levels were associated with risks of SCZ (odds ratio [OR] = 1.12, PGSMR = 1.73 × 10−3) and BD-I (OR = 1.14, PIVW = 5.23 × 10−3) after Bonferroni correction. These associations were statistically significant when using IVW analysis (SCZ: OR = 1.11, PIVW = 2.74 × 10−3; BD-I: OR = 1.13, PIVW = 9.44 × 10−3). Furthermore, no significant horizontal pleiotropy was found by sensitivity analysis, and leave-one-out analyses showed no specific SNP affected the overall estimate. However, genetically determined plasma Hcy levels were not causally associated with MDD, BD, or BD-II risks.ConclusionOur results suggest that elevated plasma Hcy levels may increase the risk of SCZ or BD-I. Further randomized clinical trials are warranted to validate the MR findings in our study.

ObjectivesFatty acids (FA) are widely believed to play a role in the pathophysiology of depression. However, the causal relationships between FA and depression remain elusive and warrant further research. We aimed to investigate the potential causal relationship between FA [saturated fatty acids (SFA), mono-unsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA)] and the risk of depression using Mendelian randomization (MR) analysis.MethodsWe conducted a two-sample MR analysis using large-scale European-based genome-wide association studies (GWASs) summary data related to depression (n = 500,199 individuals) and FA [saturated fatty acids (SFA), mono-unsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA)] levels. MR analysis was performed using the Wald ratio and inverse variance-weighted (IVW) methods, and sensitivity analysis was conducted by the simple mode, weighted mode, weighted median method, and MR-Egger method.ResultsWe found the causal effects for the levels of oleic acid (OA; OR = 1.07, p = 5.72 × 10–4), adrenic acid (OR = 0.74, p = 1.01 × 10–3), α-linolenic acid (ALA; OR = 2.52, p = 1.01 × 10–3), eicosapentaenoic acid (EPA; OR = 0.84, p = 3.11 × 10–3) on depression risk, after Bonferroni correction. The sensitivity analyses indicated similar trends. No causal effect between the levels of SFA and depression risk was observed.ConclusionOur study suggests that adrenic acid and EPA are protective against the risk of depression, while OA and ALA are potential risk factors for depression. Nonetheless, the underlying mechanisms that mediate the association between these FAs and depression risk should be investigated in further experiments.

The aim of this study was to investigate the effectiveness of cognitive behavioral therapy (CBT) on improving the cognitive function in minor depression (MiD) and major depression (MaD). The study will constitute a placebo-controlled single-blind parallel-group randomized controlled trial. The selected participants will be randomly allocated into one of two parallel groups with a 1:1 ratio: the CBT-based group and the general health education group. CBT significantly alleviated depressive symptoms of MiD and MaD at 12 weeks (p < 0.001), and the treatment effect was maintained for at least 12 months (p < 0.001). Interestingly, CBT significantly promotes more cognitive function of MiD and partial cognitive function of MaD at 12 weeks in the intervention group than in the control group (p < 0.01). CBT can alleviate depressive symptoms of both minor and MaDs. The effectiveness of CBT is different on improving the cognitive function in MiD and MaD.