Potential association between mobile phone usage duration and postpartum depression risk: Evidence from a Mendelian randomization study

Abstract

The widespread adoption of mobile phones in daily life has raised concerns regarding their impact on mental health, including among postpartum women. Considering the rising prevalence of postpartum depression (PPD) and the pervasive use of mobile phones in modern society, this study aimed to rigorously investigate the causal relationship between mobile phone use duration and the risk of developing PPD. Data were collected through an online survey assessing mobile phone usage and mental health among postpartum women. The survey’s reliability and validity were evaluated using Statistical Package for the Social Sciences software. In total, 2015 participants completed the survey. To explore causal relationships, genetic data were sourced from open-access databases, and two-sample Mendelian randomization (MR) techniques were employed. Statistical analysis, including chi-square tests, revealed a significant association between higher mobile phone use and lower incidence of PPD. MR analysis supported these findings, indicating a protective effect of mobile phone use against PPD (P < .05 based on inverse variance weighting and the weighted median method). This MR-based study provides evidence that increased mobile phone use is associated with a decreased risk of PPD, suggesting that mobile phones could serve as an effective tool for PPD prevention. These findings highlight the importance of evidence-based evaluations of lifestyle factors in mental health research.

1. Introduction

Mobile phone use is now pervasive, being deeply integrated into daily life, raising concerns regarding its health implications, particularly for mental health.^[1–3] Postpartum depression (PPD), a major global mental health challenge among women, has been associated with various environmental and behavioral factors, including digital device use.^[4–6] However, the relationship between mobile phone use and PPD remains underexplored.

PPD markedly impacts maternal health, affecting mother–newborn bonding and the mother’s functional and emotional well-being.^[7,8] Although traditional risk factors for PPD include hormonal changes, lack of support, and prior mental health issues, emerging evidence suggests that lifestyle factors, including mobile phone usage, may also play a role.^[9]

Mobile phone use can disrupt daily routines, influence sleep patterns, and alter social interactions, all critical during the postpartum period.^[10,11] Some studies indicate that excessive screen time may exacerbate anxiety and depression,^[12] whereas others suggest that mobile phones could enhance access to social support and health information, potentially alleviating feelings of isolation among new mothers.^[13]

Understanding the relationship between mobile phone use and PPD is crucial given the widespread adoption of mobile technology and the increasing incidence of PPD. This study employs a two-sample Mendelian randomization (MR) approach to explore the potential causal link between mobile phone use and PPD. MR enables causal assessment using genetic variants as proxies for exposure, thereby mitigating confounding factors commonly observed in observational studies.^[14] This method aimed to provide robust insights into whether mobile phone use duration influences PPD risk alongside valuable data to extend discussions on digital health interventions.

2. Materials and methods

2.1. Survey

The study was approved by the Ethics Committee of the Jiaxing Maternity and Children Health Care Hospital. Data collection was conducted through an online survey via Wenjuanxing (https://www.wjx.cn/). Data were anonymously collected from postpartum women 6-weeks postdelivery, having recovered well, with voluntary informed consent obtained from all participants. The survey comprised 21 questions, divided into 2 main categories: (1) demographic information and mobile phone usage and (2) the Edinburgh postnatal depression scale. Based on preliminary studies, the clinical threshold for screening postpartum depression in Chinese women was set at 9/10.^[15,16] Statistical Package for the Social Sciences software was used to determine the validity of the questionnaire, employing factor analysis to automatically select extracted factors. Additionally, Cronbach alpha was used to assess the questionnaire’s consistency and reliability.

2.2. Genomic insights into mobile phone use duration

Summary statistics regarding mobile phone use duration were sourced from genome-wide association studies (GWAS) in a specific database (https://gwas.mrcieu.ac.uk/). This GWAS analysis involved 456,972 individuals assessing 9,851,867 distinct single nucleotide polymorphism (SNPs), with the study population predominantly of European descent.

2.3. Genomic analysis of postpartum depression

Summary statistics for postpartum depression were sourced from the aforementioned GWAS database. The sample included 67,205 mothers with complete postpartum follow-up records, including 7604 cases and 59,601 controls, with approximately 16,376,275 SNPs evaluated. The study focused on individuals of European descent. Postpartum depression was defined using endpoint definitions approved by the FinnGen study’s clinical expert groups, comprising leading experts in their respective medical fields. The FinnGen study has provided a robust framework for defining medical conditions; thus, its use ensured the consistency and reliability of our diagnostic criteria.

2.4. Study methodology of MR

In this research, we applied a bi-directional two-sample MR approach to explore the hypothesized causative nexus between mobile phone use duration and postpartum depression. Within the MR paradigm, genetic variants are harnessed as surrogate markers for potential risk factors. For the derivation of credible causal inferences using instrumental variables (IVs), adherence to 3 cardinal tenets is imperative:

1. There is a direct correlation between genetic variation and exposure.

2. Absence of any linkage between these genetic variants and confounders that could bias the exposure-outcome interplay.

3. Exclusivity in the influence of the genetic variation-driven exposure on the outcome.

2.5. IV selection

We set the significance level for IVs associated with each characteristic at 1 × 10⁻⁵ based on recent findings.^[17] Using the TwoSampleMR package in R, SNPs were optimized. The clumping parameter was activated, with a secondary significance level set at 1 × 10⁻⁵. The criterion for linkage disequilibrium was set at r² = 0.001, and the clumping proximity was set at 10,000 kb. To mitigate bias from suboptimal instruments, we computed R² and F statistics for each SNP using the following formulas:

$${\displaystyle \begin{array}{l}{\displaystyle R^2=\frac{2{\mathrm{\beta }}_{exposure}^{2}ea{f}_{exposure}(1-ea{f}_{exposure})}{\begin{array}{lll}& {\displaystyle 2{\mathrm{\beta }}_{exposure}^{2}ea{f}_{exposure}(1-ea{f}_{exposure})}& {\displaystyle +2s{e}_{exposure}^{2}samplesiz{e}_{exposure}ea{f}_{exposure}(1-ea{f}_{exposure})}\end{array}}}\end{array}}$$

$${\displaystyle \begin{array}{l}{\displaystyle F=\frac{R^2(samplesiz{e}_{exposure}-2)}{1-R^2}}\end{array}}$$

In these formulas,

• β_exposure represents the beta coefficient of exposure.

• eaf_exposure is the effect of allele frequency of exposure.

• se_exposure represents the standard error of exposure.

• samplesize_exposure indicates the sample size of the exposure group.

SNPs with an F-statistic < 10 were excluded from our analysis to mitigate weak instrument bias, which can inflate type I error rates and yield unreliable estimates.

2.6. Statistical approach

Analyses were conducted using the R programming environment (version 4.3.1). Causal relationships between mobile phone use duration and postpartum depression were evaluated using inverse variance weighting (IVW), weighted median, and mode-based techniques, primarily through the TwoSampleMR package. Heterogeneity among IVs was assessed using Cochran Q statistic, with a P > .05 indicating nonsignificant heterogeneity. In cases involving significant heterogeneity, a random-effects IVW model replaced the fixed-effects approach. The MR-Egger (a method within MR analysis) method addressed potential horizontal pleiotropy, with significance in its intercept indicating the presence of pleiotropy. The Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) technique identified and excluded potential pleiotropic outliers. Funnel plots were included to assess publication bias and validate result consistency and robustness.

3. Results

3.1. Demographic information and mobile phone usage analysis

The demographic information and mobile phone usage of the 2015 participants are detailed in Table S1, Supplemental Digital Content, http://links.lww.com/MD/N685. The internal consistency of the 10-item Edinburgh postnatal depression scale was confirmed using Cronbach α coefficient, yielding a high value of 0.921. Questionnaire validity was assessed using Statistical Package for the Social Sciences software, employing principal component analysis with varimax rotation. Notably, the Kaiser–Meyer–Olkin measure was exceptionally high at 0.966, suggesting robust intervariable correlations and confirming the data’s suitability for factor analysis. Bartlett test of sphericity confirmed questionnaire construct validity, with a significant value of 17,009.548 and P < .001. Further details of these results are provided in Table S2, Supplemental Digital Content, http://links.lww.com/MD/N685.

Further analysis revealed that various demographic and lifestyle factors were correlated with PPD. Notably, older mothers (≥35 years) exhibited significantly higher PPD rates compared with younger mothers (P = 1.90E − 26). Divorced or widowed status was significantly associated with elevated PPD rates, highlighting the substantial impact of marital disruption on mental health. Poor sleep quality (P = 6.25E − 87) and unemployment or part-time work (P = 1.46E − 171) were significantly associated with higher PPD rates. Educational level, number of pregnancies, number of children, and feeding style did not significantly impact PPD rates, whereas increased mobile phone use duration significantly reduced PPD incidence (P-value = 1.23E − 154). Detailed analysis results are provided in Table S3, Supplemental Digital Content, http://links.lww.com/MD/N685.

To focus on the relationship between mobile phone use duration and PPD, the survey was refined by excluding questionnaires from older mothers (≥35 years) and those with divorced or widowed status, poor sleep quality, and unemployed or part-time worker status. Following these exclusions, 1181 remaining questionnaires were analyzed. In this refined dataset, although most factors showed no significant association with PPD (P > .05), increase mobile phone usage duration was significantly correlated with lower PPD incidence (P-value = 1.55E − 08).

3.2. Impact of mobile phone use duration on PPD

Based on predefined IV selection criteria, 163 SNPs were used as IVs, with palindromic SNPs exhibiting intermediate allele frequencies removed. Detailed information regarding the selected SNPs and their characteristics is provided in Table S4, Supplemental Digital Content, http://links.lww.com/MD/N685. Our analysis revealed a statistically significant negative correlation between mobile phone use duration and PPD based on the IVW method (odds ratio [OR] = 1.60, b = 0.47, P < .01). A similar protective effect was confirmed through the weighted median method, indicating decreased risk (OR = 1.42, b = 0.35, P = .01), as depicted in Figure 1 and Table S5, Supplemental Digital Content, http://links.lww.com/MD/N685.

Figure 1.

(A) Forest plot showing the causal association between mobile phone use duration and postpartum depression. (B) Scatter plot illustrating the causal association between length of mobile phone use and postpartum depression. (C) Funnel plot assessing notable heterogeneity in the observed associations.

Cochran IVW Q test results indicated no significant heterogeneity among the IVs (Table S6, Supplemental Digital Content, http://links.lww.com/MD/N685). MR-Egger (a method within MR analysis) regression intercept analysis did not reveal significant directional horizontal pleiotropy (Table S7, Supplemental Digital Content, http://links.lww.com/MD/N685). Additionally, the Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) global test did not identify significant outliers (Table S8, Supplemental Digital Content, http://links.lww.com/MD/N685), implying minimal horizontal pleiotropy in the association.

4. Discussion

The impact of mobile phone use on health has been a consistent focus in the medical community. This study investigated the potential causal relationship between mobile phone use duration and PPD through a questionnaire survey conducted among postpartum women coupled with MR analysis. Integrating observational data with MR analysis provides a genetic basis for enhancing our understanding of this causal relationship. This comprehensive approach integrates community perceptions with robust genetic insights, offering a holistic perspective on potential causal links while strengthening the depth and validity of the findings.

Our analysis revealed a significant association: increased mobile phone use duration was linked to reduced PPD risk. This contrasts with previous studies predominantly focusing on the negative impacts of mobile phone use on mental health.^[18,19] However, our findings suggest that moderate mobile phone use may decrease PPD risk, as confirmed through MR techniques, including IVW and the weighted median method.

The potential reduction in PPD risk associated with increased mobile phone use can be attributed to several factors supported by existing literature. Increased mobile phone use can facilitate improved access to social support and communication, which is crucial for mental health during the postpartum period.^[20] Research by Martina et al (2022) showed that digital access to social support significantly correlates with reduced depression symptoms among postpartum women, providing immediate contact with friends, family, and online communities that may offer emotional support and information that alleviate feelings of isolation and stress commonly experienced during the postpartum period.^[21] Moreover, mobile phones serve as platforms for mental health interventions, such as mindfulness apps, which are effective in reducing depression symptoms.^[22] Indeed, a systematic review performed by Firth et al (2017) highlighted the efficacy of mobile health apps in improving mental health, with such tools delivering therapeutic interventions alongside user engagement and adherence.^[3] These interventions may include cognitive-behavioral therapy techniques, relaxation exercises, and mood tracking, which may be beneficial for mothers during the postpartum phase. Therefore, mobile phones used to enhance social connections and access mental health resources could potentially lower PPD risk.

The rigorous methodological framework incorporating the two-sample MR approach strengthens the present study, supporting the validity of our causal inferences. Nevertheless, our study has limitations. For instance, the findings’ applicability may be confined to specific demographic groups, necessitating further investigation across a broader population. Although the survey method provides valuable insights from participants, its reliance on the respondents’ subjective feelings and personal health awareness introduces potential biases, as individuals may inaccurately assess their health issues based on personal judgment or medical knowledge gaps. Additionally, despite excluding certain confounders, such as older mothers and those with poor sleep quality, other unmeasured variables could still exert an influence. Therefore, future research should validate the present results in more diverse populations and consider additional potential confounding factors. Furthermore, acknowledging the limitations of the current study, future research should aim to collect more genetic data from non-European populations, such as those in China, to verify and expand upon our findings, enhancing the generalizability and applicability of the results.

In summary, this study presents new genetic evidence regarding the relationship between mobile phone use duration and PPD, underscoring the importance of evidence-based approaches for deepening our understanding of health–behavior interventions. Overall, these findings suggest promising new directions for PPD prevention and intervention.

5. Conclusions

This study indicates that increased mobile phone usage may mitigate the risk of PPD, likely by enhancing access to social support and mental health resources. These findings suggest a possible role for mobile phones in PPD prevention strategies. However, given the specific demographics studied, further research across diverse populations is required to validate this study’s conclusions.

Author contributions

Data curation: Siyi Zhang, Liqin Jin.

Formal analysis: Siyi Zhang, Liqin Jin.

Investigation: Liqin Jin.

Writing – original draft: Keng Ling.

Writing – review & editing: Jianguo Wang.