ADHD has traditionally been diagnosed more frequently in males than females, with differences observed in symptom presentation.
Males often display more obvious hyperactive-impulsive behaviors, while females may exhibit more subtle inattentive symptoms.
This discrepancy in diagnostic rates and symptom manifestation highlights the importance of investigating gender differences in ADHD.
Understanding these variations is crucial for improving diagnostic accuracy, developing targeted interventions, and ensuring that affected individuals of both genders receive appropriate support and treatment.
Young, S., Uysal, O., Kahle, J., Gudjonsson, G. H., Hollingdale, J., Cortese, S., Sakalli-Kani, A., Greer, B., Cocallis, K., Sylver, N., Yilmaz, U. E., Semerci, B., & Kilic, O. (2024). A systematic review and meta-analysis comparing the severity of core symptoms of attention-deficit hyperactivity disorder in females and males. Psychological Medicine. Advance online publication. https://doi.org/10.1017/S0033291724001600
Key Points
- The study found no significant differences in ADHD symptom severity between males and females when using clinical diagnostic interview data for both children and adults.
- Rating scale data showed some small but significant gender differences, with boys having more severe hyperactivity/impulsivity symptoms than girls in childhood, and men having more severe inattention symptoms than women in adulthood.
- The overall effect sizes for gender differences were small across all analyses.
- There may be gender biases in the referral and assessment process for ADHD that contribute to perceived differences in prevalence rates between males and females.
- The findings challenge previous assumptions about substantial gender differences in ADHD symptom presentation and severity.
- Limitations include high heterogeneity across studies and potential publication bias for some analyses.
- Understanding gender differences in ADHD presentation is crucial for improving identification and treatment, especially for females who may be underdiagnosed.
Rationale
Previous meta-analyses comparing ADHD symptom severity between males and females were conducted over 20 years ago and had methodological limitations (Gaub & Carlson, 1997; Gershon, 2002).
Since then, substantial changes have occurred in diagnostic criteria for ADHD, including the recognition that it can persist into adulthood.
Additionally, there has been increased interest in understanding ADHD presentation in females, who may be underdiagnosed (Willcutt, 2012).
This study aimed to provide an updated and more refined analysis of gender differences in ADHD symptom severity across the lifespan using current diagnostic criteria.
The researchers sought to examine potential differences between clinical diagnostic interviews and rating scale data, as well as compare findings for children and adults.
Method
The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines.
The protocol was registered on PROSPERO (CRD42020103830). The researchers also adhered to MOOSE guidelines for reporting meta-analyses of observational studies.
Search strategy and terms
The researchers searched PubMed, PsycINFO, and Scopus databases for articles published through May 28, 2021.
Search terms related to attention-deficit/hyperactivity disorder (ADHD) and gender/sex were used, including variations like “attention deficit disorder,” “hyperkinetic disorder,” “female,” “male,” etc.
Boolean operators were employed to combine terms. No age restrictions were applied. The full search strings are provided in the supplementary materials.
Inclusion and exclusion criteria
Included studies were:
- Peer-reviewed articles in English
- Primary research on ADHD symptoms using DSM-IV, DSM-IV-TR, or DSM-5 criteria
- Reported results separately for males and females
Excluded were studies:
- Using diagnostic criteria earlier than DSM-IV
- Focusing on conditions other than ADHD
- Presenting only aggregated data for males and females
- Reporting data from the same dataset as another included study (in which case the most recent/largest sample was used)
Extraction of Data
Two independent reviewers extracted data into an Excel spreadsheet, including:
- Study details (author, year, location)
- Sample characteristics (size, age, sex, setting)
- Assessment methods (rater source, tools used)
- Diagnostic criteria
- Symptom severity scores and standard deviations
For consistency, only parent-rated data was included for children. Studies were categorized as child or adult based on mean sample age (<17 years = child).
Statistical measures
The researchers used Jamovi statistical software to conduct random-effects meta-analyses.
Standardized mean differences were calculated as effect sizes. Heterogeneity was assessed using I2 statistics, with I2 >75% considered high heterogeneity.
Publication bias was evaluated using funnel plots and Egger’s test. Sensitivity analyses were conducted excluding poor-quality studies.
Results
The researchers conducted 15 separate meta-analyses examining:
- Total sample data (aggregating rating scales and clinical interviews across lifespan)
- Rating scale data only
- Clinical interview data only
For each category, they analyzed:
- Inattention symptoms
- Hyperactivity/impulsivity symptoms
- Combined ADHD presentation
Key findings
Total sample:
- No significant gender differences in inattention severity
- Males had significantly more severe hyperactivity/impulsivity symptoms (small effect size)
- No significant differences in combined presentation
Rating scales:
Children:
- No significant gender differences in inattention
- Boys had significantly more severe hyperactivity/impulsivity symptoms (small effect size)
- No significant differences in combined presentation
Adults:
- Men had significantly more severe inattention symptoms (small effect size)
- No significant gender differences in hyperactivity/impulsivity
- No significant differences in combined presentation
Clinical interviews:
- No significant gender differences for any symptom domain in children or adults
All significant differences had small effect sizes (standardized mean difference <0.50).
High heterogeneity was found in most analyses. Publication bias was detected for some total sample and rating scale analyses.
Insight
This study challenges previous assumptions about substantial gender differences in ADHD symptom presentation and severity.
The finding of no significant differences when using clinical diagnostic interviews for both children and adults is particularly noteworthy.
This suggests that when thorough clinical assessments are conducted, males and females with ADHD may present with similar symptom severity.
The discrepancy between clinical interview and rating scale results raises important questions about potential biases in ADHD assessment and referral processes.
Rating scales, which are often used for screening or monitoring symptoms, may be more susceptible to gender stereotypes or differing behavioral expectations for males and females.
This could lead to over-identification of externalizing symptoms in males and under-recognition of ADHD in females.
The small but significant gender differences found in rating scale data align with some previous research showing higher rates of hyperactivity/impulsivity in boys and more inattention in adult men.
However, the effect sizes were small, emphasizing that individual variation is likely more important than gender in determining symptom presentation.
These findings extend previous research by providing a more nuanced understanding of potential gender differences across development and assessment methods.
They highlight the importance of comprehensive clinical evaluations and caution against relying solely on rating scales for diagnosis.
Further research is needed to:
- Investigate factors contributing to discrepancies between rating scale and clinical interview results
- Examine how gender biases may influence ADHD referral and assessment processes
- Explore potential differences in functional impairment or comorbidities between males and females with ADHD
- Develop and validate gender-sensitive ADHD assessment tools
Implications
The results have significant implications for ADHD assessment, diagnosis, and treatment across clinical and educational settings.
The lack of substantial gender differences in symptom severity when using clinical interviews suggests that current diagnostic criteria may be appropriate for both males and females.
However, clinicians should be aware that rating scales may overestimate gender differences and should not be used as the sole basis for diagnosis.
The findings emphasize the need for increased awareness of ADHD presentation in females, who may be underdiagnosed due to biases in referral processes or expectations about symptom expression.
Educators, parents, and healthcare providers should be educated about potential gender differences in ADHD manifestation to improve identification of affected females.
The small effect sizes for gender differences highlight the importance of individualized assessment and treatment planning.
Clinicians should focus on each person’s unique symptom profile and functional impairments rather than making assumptions based on gender.
The discrepancy between rating scale and clinical interview results underscores the value of comprehensive, multi-method assessments for ADHD.
Best practice should include thorough clinical interviews, consideration of developmental history, and gathering information from multiple informants when possible.
For researchers, these findings suggest that gender should be carefully considered as a variable in ADHD studies.
Separate analyses for males and females may reveal important nuances in symptom presentation or treatment response that could be obscured in combined samples.
Strengths
The study had many methodological strengths including:
- Large sample size (18,408 participants across 52 studies)
- Inclusion of both child and adult populations
- Separate analyses for rating scales and clinical interviews
- Use of current diagnostic criteria (DSM-IV and later)
- Adherence to PRISMA and MOOSE guidelines for systematic reviews and meta-analyses
- Comprehensive search strategy across multiple databases
- Independent data extraction by multiple reviewers
- Assessment of study quality using validated tools
- Sensitivity analyses excluding poor-quality studies
- Examination of publication bias
Limitations
This study also had several methodological limitations, including:
- High heterogeneity across studies limits the generalizability of some findings
- Potential publication bias detected for some analyses
- Inclusion of only English-language studies may have excluded relevant research
- Inability to control for all potential confounding variables (e.g., ADHD subtype, comorbidities)
- Lack of data on functional impairment or quality of life outcomes
- Limited number of studies for some subgroup analyses, particularly for adults
- Inability to conduct meta-regression due to insufficient data
- Exclusion of unpublished studies may have introduced bias
- Reliance on mean ages to categorize child vs. adult studies may have led to some misclassification
The limitations related to heterogeneity and potential publication bias suggest that the results should be interpreted cautiously, particularly for subgroup analyses with fewer studies.
The focus on symptom severity alone, without consideration of functional impairment or comorbidities, may not capture the full complexity of gender differences in ADHD presentation.
Additionally, the lack of non-English studies and unpublished data could limit the global applicability of the findings.
References
Primary reference
Young, S., Uysal, O., Kahle, J., Gudjonsson, G. H., Hollingdale, J., Cortese, S., Sakalli-Kani, A., Greer, B., Cocallis, K., Sylver, N., Yilmaz, U. E., Semerci, B., & Kilic, O. (2024). A systematic review and meta-analysis comparing the severity of core symptoms of attention-deficit hyperactivity disorder in females and males. Psychological Medicine. Advance online publication. https://doi.org/10.1017/S0033291724001600
Other references
Gaub, M., & Carlson, C. L. (1997). Gender differences in ADHD: A meta-analysis and critical review. Journal of the American Academy of Child & Adolescent Psychiatry, 36(8), 1036-1045. https://doi.org/10.1097/00004583-199708000-00011
Gershon, J., & Gershon, J. (2002). A meta-analytic review of gender differences in ADHD. Journal of attention disorders, 5(3), 143-154. https://doi.org/10.1177/108705470200500302
Willcutt, E. G. (2012). The prevalence of DSM-IV attention-deficit/hyperactivity disorder: a meta-analytic review. Neurotherapeutics, 9(3), 490-499. https://doi.org/10.1007/s13311-012-0135-8
Keep Learning
- How might societal gender expectations influence the identification and diagnosis of ADHD in males versus females?
- What factors could contribute to the discrepancy between rating scale and clinical interview results for gender differences in ADHD symptoms?
- How could the findings of this study impact current ADHD assessment practices in schools and clinical settings?
- What are potential explanations for the shift in gender differences from hyperactivity/impulsivity in childhood to inattention in adulthood observed in rating scale data?
- How might these results inform the development of more gender-sensitive ADHD diagnostic criteria or assessment tools?
- What ethical considerations should researchers and clinicians keep in mind when studying or discussing gender differences in ADHD?
- How could unconscious biases among parents, teachers, or clinicians affect the referral and diagnosis process for ADHD in males versus females?
- What implications do these findings have for understanding the true prevalence of ADHD in females compared to current estimates?
- How might the results of this study impact public perception and awareness of ADHD in females?
- What are potential long-term consequences of underdiagnosis or misdiagnosis of ADHD in females based on gender biases in assessment?
