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Defense Mechanisms

Psychiatry and Psychology · NLM MeSH · updated 2026-11-04 · version 1

Citations verified against PubMedNot yet clinician-reviewed10 referencesApproximately 5 min read

Unconscious process used by an individual or a group of individuals in order to cope with impulses, feelings or ideas which are not acceptable at their conscious level; various types include reaction formation, projection and self

Table of Contents

1. Definition2. Research landscape3. Reading the evidence4. Open-access studies5. Key reviews6. References7. About this article

Definition and research guide

This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.

Content available: 4 complete abstracts (866 words), 10 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.

Definition

Unconscious process used by an individual or a group of individuals in order to cope with impulses, feelings or ideas which are not acceptable at their conscious level; various types include reaction formation, projection and self reversal.

Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.

Also known as: Mechanisms, Defense.

Where it fits in the MeSH classification

Broader topics
Behavior and Behavior Mechanisms
Narrower topics
Acting Out; Denial, Psychological; Displacement, Psychological; Fantasy; Helplessness, Learned; Identification, Psychological; Information Avoidance; Perceptual Defense; Procrastination; Projection; Rationalization; Regression, Psychology; Repression, Psychology; Sublimation, Psychological

Research landscape

PubMed indexes 57,638 records tagged with the MeSH heading “Defense Mechanisms” (counts retrieved 2026-10-31). 8,839 of them (15.3%) were published from 2020 onward, and the busiest period so far is through 1999 with 26,623 records.

Reviews account for 4,979 records (8.6%) and meta-analyses for 215. Randomized controlled trials number 775 (1.3%) as a share of all records on the topic. Randomized trials make up only a small share of this literature, so much of what is known comes from laboratory, observational or descriptive work.

PubMed records by publication periodthrough 1999: 26,623 records; 2000-2009: 10,147 records; 2010-2019: 12,029 records; 2020 onward: 8,839 records26,623through 199910,1472000-200912,0292010-20198,8392020 onward
Records in PubMed indexed with this heading, by publication period. Real counts from NCBI E-utilities; the final period covers only part of the current year. Volume reflects how much has been published, not how strong the evidence is.
Show the data
PeriodRecords
through 199926,623
2000-200910,147
2010-201912,029
2020 onward8,839
Share of records by publication typeReviews: 8.6 percent; Meta-analyses: 0.4 percent; Randomized controlled trials: 1.3 percentReviews8.6% (4,979)Meta-analyses0.4% (215)Randomized controlled trials1.3% (775)
Share of all PubMed records on this heading that carry each publication type. Types overlap with other records, so the shares do not sum to 100%.
Publication-type chart data
Publication types among 57,638 PubMed records
TypeRecordsShare
Reviews4,9798.6%
Meta-analyses2150.4%
Randomized controlled trials7751.3%

Method: PubMed query "Defense Mechanisms"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-31.

Reading the evidence in psychiatry and psychology

Research on mental health and behaviour relies on questionnaires, interviews and rating scales rather than physical measurements, so how a condition was defined and measured shapes every result. Many studies are observational or small, placebo responses can be large, and findings in one group or culture may not carry over to another. Nothing on this page is advice about diagnosis or treatment; anyone worried about their mental health should talk to a qualified clinician. Check how outcomes were measured, who took part and how long they were followed.

Evidence from open-access studies

These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.

Study comparison — selected abstracts, not a systematic review
Study / authorsYearSource label / designEurope PMC citationsLicence / source
Men's Mental Health Matters: The Impact of Traditional Masculinity Norms on Men's Willingness to Seek Mental Health Support; a Systematic Review of Literature
Mokhwelepa LW, Sumbane GO
2025Systematic review
Design not recorded in structured metadata
34cc by
PMID 40421591 · DOI · PMC12117241
Mental health help-seeking among Korean men: the influence of stigma, masculine norms, and face
Kim S, Kim D
2025Research article
Design not recorded in structured metadata
10cc by
PMID 40317029 · DOI · PMC12046740
Sex/gender entanglement: A problem of knots and buckets
Maney DL, Duchesne A, Grossi G
2025Review article
Design not recorded in structured metadata
6cc by
PMID 41168807 · DOI · PMC12577278
Exploring the Intersection of Gender Identity and Eating Behaviours in Gender-Diverse Populations
Meneguzzo P, Biscaro M, Vozzi L, Bonato M, Scala A, Miscioscia M, et al.
2026Research article
Design not recorded in structured metadata
4cc by
PMID 41205200 · DOI · PMC13048733

Men's Mental Health Matters: The Impact of Traditional Masculinity Norms on Men's Willingness to Seek Mental Health Support; a Systematic Review of Literature [1]

Systematic review Mokhwelepa LW, Sumbane GO · · 2025 · cited 34 times (Europe PMC)

Abstract reading summary — source excerpts
Opening excerpt
Men's mental health is a focus area for improving population health worldwide.
Closing excerpt
Traditional masculinity norms significantly deter men from seeking mental health support, highlighting the need for culturally sensitive interventions that address these barriers.
Interpretation limits
Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (212 words)

Men's mental health is a focus area for improving population health worldwide. Traditional masculine norms among men have been reported to make them more susceptible to mental health issues. This study aims to review existing literature on how traditional masculinity norms influence men's willingness to seek mental health support. This review followed stages of systematic review. The review search was initiated in February 2024. The search process was conducted on electronic databases such as PubMed, PsycINFO, Science Direct, and Google Scholar to identify relevant studies published in English between 2000 and 2024. The search terms included "traditional masculinity norms," "men's mental health," "help-seeking behavior," and "barriers to mental health care." Studies were selected based on their relevance to the topic. The inclusion criteria were studies focusing on adult men and examining the relationship between traditional masculinity norms and mental health help-seeking behaviors. Exclusion criteria included studies focusing on children, adolescents, or women and nonempirical articles. Data extraction covered study details, design, population characteristics, and key findings. This study included 47 relevant studies. Two key themes emerged, namely: masculinity and mental health (impact on mental health); and barriers to seeking help. Traditional masculinity norms significantly deter men from seeking mental health support, highlighting the need for culturally sensitive interventions that address these barriers.

Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 40421591 · DOI · PMC12117241

Mental health help-seeking among Korean men: the influence of stigma, masculine norms, and face [2]

Research article Kim S, Kim D · · 2025 · cited 10 times (Europe PMC)

Abstract reading summary — source excerpts
Opening excerpt
BackgroundPrevious studies have found that Asians and men are more susceptible to the stigma and stereotypes associated with mental illness.
Closing excerpt
The ultimate goal is to foster a social environment that encourages open discussion about mental illness, masculinity, and Asian values.
Interpretation limits
Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (194 words)

BackgroundPrevious studies have found that Asians and men are more susceptible to the stigma and stereotypes associated with mental illness. This social perception makes it difficult for Korean men to seek professional psychological help even when they desperately need it. The primary objectives of this study were to investigate barriers to mental health help-seeking among Korean men and to identify the role of sociocultural factors.MethodsA total of 341 Korean men aged 19 to 59 years participated in an online survey, which included questionnaires on loss of face, self-stigma of seeking help, attitudes toward seeking professional psychological help, and conformity to masculine norms. Structural Equation Modeling was used to explore the relationships among these variables.ResultsThe results revealed that loss of face indirectly affected attitudes toward seeking professional psychological help (ATSPPH) through its mediating effect on self-stigma. Loss of face did not directly influence ATSPPH. Furthermore, conformity to masculine norms negatively affected ATSPPH, and self-stigma mediated this relationship.ConclusionThese findings highlight the importance of understanding the influence of sociocultural factors in encouraging Korean men to seek help. The ultimate goal is to foster a social environment that encourages open discussion about mental illness, masculinity, and Asian values.

Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 40317029 · DOI · PMC12046740

Sex/gender entanglement: A problem of knots and buckets [3]

Review article Maney DL, Duchesne A, Grossi G · · 2025 · cited 6 times (Europe PMC)

Abstract reading summary — source excerpts
Opening excerpt
When used as variables in biomedical research, sex and gender can be difficult to operationalize and measure.
Closing excerpt
In addition, we advocate for attention to variation within sex/gender, which is more informative in investigations of mechanism than comparing means across sex/gender categories.
Interpretation limits
Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (267 words)

When used as variables in biomedical research, sex and gender can be difficult to operationalize and measure. Questions have arisen about whether either category is stable or causally meaningful in a research context. Here, we discuss some of the limitations of using both or even one of these categories in correlational or experimental work. We argue that attempting to draw a distinction between sex and gender can reignite the nature/nurture debate, inadvertently bringing outdated metaphors and assumptions about innateness and causation into our research. Many researchers, including ourselves, have described sex and gender as separate collections of causal factors (which we describe as a "bucket" metaphor) or as entangled (a "knot" metaphor). Because they regard sex and gender as conceptually separable and internally consistent, such metaphors have limited value for understanding the drivers of diversity in our data. Rather than continuing to reify sex and gender as distinct buckets or threads of explanatory variables, we call for deconstruction of these categories by focusing instead on clearly operationalized, instantiating variables that researchers can manipulate or measure. Our proposed approach differs from recent, similar calls in that we are not suggesting the exclusion of a sex/gender category from statistical models; instead, we recommend keeping it-not as a representation of biological reality, but as a tool used under a careful set of assumptions. We provide example datasets to illustrate how a sex/gender category can, when thoughtfully operationalized, be used to improve statistical rigor and inferential precision. In addition, we advocate for attention to variation within sex/gender, which is more informative in investigations of mechanism than comparing means across sex/gender categories.

Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 41168807 · DOI · PMC12577278

Exploring the Intersection of Gender Identity and Eating Behaviours in Gender-Diverse Populations [4]

Research article Meneguzzo P, Biscaro M, Vozzi L, Bonato M, Scala A, Miscioscia M, et al. · · 2026 · cited 4 times (Europe PMC)

Abstract reading summary — source excerpts
Opening excerpt
BackgroundGender-diverse individuals are at elevated risk for disordered eating, shaped by body dissatisfaction, gender dysphoria, and minority stress.
Closing excerpt
Clinicians should consider how masculinity- and femininity-linked eating patterns shape assessment and intervention.
Interpretation limits
Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (193 words)

BackgroundGender-diverse individuals are at elevated risk for disordered eating, shaped by body dissatisfaction, gender dysphoria, and minority stress. The roles of gender identity and expression, however, remain underexplored in clinical samples. This study examined how self-perceived masculinity, femininity, and gender variance relate to eating behaviours in gender-diverse adults seeking gender-affirming care.MethodsEighty-four adults assigned female (n = 50) or male (n = 34) at birth were recruited from a regional gender incongruence clinic. Participants self-identified as male (n = 44), female (n = 30), or non-binary (n = 10); 36 were receiving gender-affirming hormone therapy (GAHT). They completed the Three-Factor Eating Questionnaire (TFEQ) and the Gender Variance Scale (GVS), assessing masculinity, femininity, and deviation from cisnormative expectations. Regression models tested associations between gender traits and eating behaviours.ResultsMasculinity was positively associated with cognitive restraint, while femininity correlated with emotional and uncontrolled eating. Gender variance was not significantly related to TFEQ; however, exploratory analyses suggested a modest quadratic trend with dysregulated eating. Eating behaviours did not differ by GAHT status.ConclusionsGender expression, more than gender variance, appears to influence eating behaviours in gender-diverse individuals. Clinicians should consider how masculinity- and femininity-linked eating patterns shape assessment and intervention.

Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 41205200 · DOI · PMC13048733

Key reviews and meta-analyses

The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.

  • Research article Gender differences in depression in representative national samples: Meta-analyses of diagnoses and symptoms [5]
    Salk RH, Hyde JS, Abramson LY · Psychol Bull · 2017 · cited 1,817 times (Europe PMC)
  • Research article Gender differences in emotion expression in children: a meta-analytic review [6]
    Chaplin TM, Aldao A · Psychol Bull · 2013 · cited 527 times (Europe PMC)
  • Research article Emotion Regulation Strategies in Depressive and Anxiety Symptoms in Youth: A Meta-Analytic Review [7]
    Schäfer JÖ, Naumann E, Holmes EA, Tuschen-Caffier B, Samson AC · J Youth Adolesc · 2017 · cited 489 times (Europe PMC)
  • Research article A meta-analytic review of sex differences in facial expression processing and their development in infants, children, and adolescents [8]
    McClure EB · Psychol Bull · 2000 · cited 476 times (Europe PMC)
  • Research article Systematic review and meta-analysis of prevalence studies in transsexualism [9]
    Arcelus J, Bouman WP, Van Den Noortgate W, Claes L, Witcomb G, Fernandez-Aranda F · Eur Psychiatry · 2015 · cited 273 times (Europe PMC)
  • Research article Assessing and Addressing Cardiovascular Health in People Who Are Transgender and Gender Diverse: A Scientific Statement From the American Heart Association [10]
    Streed CG, Beach LB, Caceres BA, Dowshen NL, Moreau KL, Mukherjee M, et al. · Circulation · 2021 · cited 246 times (Europe PMC)

References

  1. Mokhwelepa LW, Sumbane GO. Men's Mental Health Matters: The Impact of Traditional Masculinity Norms on Men's Willingness to Seek Mental Health Support; a Systematic Review of Literature. . 2025. PMID 40421591 · DOI · PMC12117241
  2. Kim S, Kim D. Mental health help-seeking among Korean men: the influence of stigma, masculine norms, and face. . 2025. PMID 40317029 · DOI · PMC12046740
  3. Maney DL, Duchesne A, Grossi G. Sex/gender entanglement: A problem of knots and buckets. . 2025. PMID 41168807 · DOI · PMC12577278
  4. Meneguzzo P, Biscaro M, Vozzi L, Bonato M, Scala A, Miscioscia M, et al.. Exploring the Intersection of Gender Identity and Eating Behaviours in Gender-Diverse Populations. . 2026. PMID 41205200 · DOI · PMC13048733
  5. Salk RH, Hyde JS, Abramson LY. Gender differences in depression in representative national samples: Meta-analyses of diagnoses and symptoms. Psychol Bull. 2017. PMID 28447828 · DOI · PMC5532074
  6. Chaplin TM, Aldao A. Gender differences in emotion expression in children: a meta-analytic review. Psychol Bull. 2013. PMID 23231534 · DOI · PMC3597769
  7. Schäfer JÖ, Naumann E, Holmes EA, Tuschen-Caffier B, Samson AC. Emotion Regulation Strategies in Depressive and Anxiety Symptoms in Youth: A Meta-Analytic Review. J Youth Adolesc. 2017. PMID 27734198 · DOI
  8. McClure EB. A meta-analytic review of sex differences in facial expression processing and their development in infants, children, and adolescents. Psychol Bull. 2000. PMID 10825784 · DOI
  9. Arcelus J, Bouman WP, Van Den Noortgate W, Claes L, Witcomb G, Fernandez-Aranda F. Systematic review and meta-analysis of prevalence studies in transsexualism. Eur Psychiatry. 2015. PMID 26021270 · DOI
  10. Streed CG, Beach LB, Caceres BA, Dowshen NL, Moreau KL, Mukherjee M, et al.. Assessing and Addressing Cardiovascular Health in People Who Are Transgender and Gender Diverse: A Scientific Statement From the American Heart Association. Circulation. 2021. PMID 34235936 · DOI · PMC8638087

About this article

Sources
NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
Verification
Every reference was resolved against PubMed on 2026-11-04; title, year and DOI matched.
Review state
automated source verified; no human expert review has been recorded yet.
Version
1, last updated 2026-11-04.

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At a glance

57,638
PubMed records on this heading
15%
published since 2020
4,979
review articles
775
randomized trials
10
verified references below

Counts come from PubMed on 2026-10-31; they show how much has been written, not how strong the evidence is.

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