Psychiatry · Medical Literature
Brain Aging in Specific Phobia: An ENIGMA-Anxiety Mega-Analysis.
Abstract
Specific phobia (SPH) is a prevalent anxiety disorder and may involve advanced biological aging. However, limited brain age research has been conducted in anxiety disorders. This mega-analysis investigated brain aging in SPH participants within the ENIGMA-Anxiety Working Group. 3D brain structural MRI scans from 17 international samples (600 SPH individuals, of whom 504 formally diagnosed and 96 questionnaire-based cases; 1134 controls; age range: 22-75 years) were processed with FreeSurfer. Brain age was estimated from 77 subcortical and cortical regions with a publicly available ENIGMA brain age model. The brain-predicted age difference (brain-PAD) was calculated as brain age minus chronological age. Linear mixed-effects models examined group differences in brain-PAD and moderation by age. No significant group difference in brain-PAD manifested (βdiagnosis [SE] = 0.37 years [0.43], p = 0.39). A negative diagnosis-by-age interaction was identified, which was most pronounced in formally diagnosed SPH (βdiagnosis-by-age = -0.08 [0.03], pFDR = 0.02). This interaction remained significant when excluding participants with anxiety comorbidities, depressive comorbidities, and medication use. Post hoc analyses revealed a group difference for formal SPH diagnosis in younger participants (22-35 years; βdiagnosis = 1.20 [0.60], p < 0.05, mixed-effects d [95% confidence interval] = 0.14 [0.00-0.28]), but not older participants (36-75 years; βdiagnosis = 0.07 [0.65], p = 0.91). Brain aging did not relate to SPH in the full sample. However, a diagnosis-by-age interaction was observed across analyses, and was strongest in formally diagnosed SPH. Post hoc analyses showed subtle advanced brain aging in young adults with formally diagnosed SPH. Taken together, these findings indicate the importance of clinical severity, impairment, and persistence, and may suggest a slightly earlier end to maturational processes or subtle decline of brain structure in SPH.
Clinical relevance
Does specific phobia (SPH) in adults associate with accelerated brain aging, as measured by the brain-predicted age difference (brain-PAD), and does chronological age moderate this relationship? __SNAPSHOT__ {"studyDesign":"Cross-sectional mega-analysis using individual-level data (linear mixed-effects models) within the ENIGMA-Anxiety Working Group framework","setting":"17 international research sites contributing neuroimaging data; multinational, multi-institutional academic settings","sampleSize":"n = 1,734 total (600 SPH [504 formally diagnosed, 96 questionnaire-based]; 1,134 healthy controls); age range 22–75 years","population":"Adults aged 22–75 years with a diagnosis of specific phobia (current or lifetime; formal DSM/ICD or questionnaire-based) and healthy controls free of all current and past mental disorders. SPH participants were excluded if they had a lifetime diagnosis of psychosis, schizophrenia, or bipolar disorder but retained if they had other comorbidities.","intervention":"Not applicable (observational exposure: DSM/ICD formal diagnosis or questionnaire-based case identification of specific phobia)","comparator":"Healthy controls (no current or past mental disorder)","primaryOutcome":"Brain-predicted age difference (brain-PAD = MRI-estimated brain age minus chronological age), derived from 77 FreeSurfer-processed subcortical and cortical regions using the publicly available ENIGMA brain age model; group difference in brain-PAD between SPH participants and healthy controls","followUp":"Not applicable (cross-sectional design)","fundingSource":"Multi-source public/non-profit funding (multiple national research councils, academic foundations); no single industry sponsor reported. Lead author (KVB) supported by Oppenheimer Memorial Trust and Boehringer Ingelheim Fonds."}
Key findings
PRIMARY OUTCOME: No statistically significant difference in brain-PAD was detected between SPH participants and healthy controls in the full sample (β = 0.37 years [SE 0.43], p = 0.39). DIAGNOSIS-BY-AGE INTERACTION: A statistically significant negative diagnosis-by-age interaction was identified in the full SPH group (β = −0.08 [SE 0.03], pFDR = 0.02), indicating that the relationship between SPH diagnosis and brain-PAD varied as a function of chronological age—with younger SPH participants showing relatively higher brain-PAD and older SPH participants showing lower brain-PAD relative to controls. This interaction was most pronounced in formally diagnosed SPH participants and remained significant after excluding those with comorbid anxiety disorders, depressive disorders, and current medication use. POST HOC ANALYSES (exploratory, median-split): In formally diagnosed SPH participants aged 22–35 years, brain-PAD was approximately +1.20 years higher than controls (SE 0.60, p < 0.05; mixed-effects Cohen's d = 0.14 [95% CI: 0.00–0.28]). No significant brain-PAD difference was detected in older formally diagnosed SPH participants (36–75 years; β = 0.07 [SE 0.65], p = 0.91). NNT/NNH: Not calculable from reported data. SYMPTOM SEVERITY: Brain-PAD was not significantly associated with SPH symptom severity centile scores (β = 0.18 [SE 0.24], p = 0.46) or STAI-T scores (specific coefficient not fully reported in abstract). Effect size context: The observed Cohen's d of 0.14 in younger formally diagnosed participants is small; for comparison, brain-PAD effects in MDD are approximately +1 year, in bipolar disorder approximately +2 years, and in psychotic disorders approximately +3 years, per referenced literature.
Practice implications
This mega-analysis established that, across a broad adult age range (22–75 years), specific phobia as a whole is NOT associated with globally accelerated brain aging as measured by brain-PAD. This is an important null finding for the field. However, the study identified a statistically significant and robust age-moderation effect: younger adults (22–35 years) with a formal clinical diagnosis of SPH show subtle advanced brain aging (~+1.20 years, d = 0.14), while this difference attenuates and disappears in older adults with SPH. This pattern could reflect earlier cessation of brain maturation or subtle early structural decline in formally diagnosed younger patients, though the cross-sectional design precludes causal or longitudinal inference. The findings apply specifically to adults aged 22–75 with formally diagnosed SPH seen in academic/research settings; children, adolescents, and community-identified cases were not represented. Questionnaire-based SPH cases showed a less pronounced interaction, underscoring the relevance of diagnostic rigor and clinical severity. The small effect size (d = 0.14) in younger patients, the post hoc and exploratory nature of the age-stratified analyses, and the cross-sectional design mean these findings cannot currently guide individual clinical decision-making or alter screening or treatment protocols. No association between brain-PAD and symptom severity was found, limiting the utility of brain-PAD as an individual prognostic biomarker in SPH. NOTE: This summary is based on the published abstract and supplementary data available from the journal and preprint; full-text access was confirmed via Wiley and medRxiv sources, though some granular table-level data may not be fully captured. __LIMITATIONS__ Cross-sectional design precludes determination of whether observed brain age differences precede, follow, or co-evolve with SPH onset or course.,Age-stratified analyses (22–35 vs. 36–75 years) were post hoc and exploratory (median-split), not pre-specified primary analyses; these findings should be interpreted as hypothesis-generating.,Mixed diagnostic ascertainment (504 formally diagnosed vs. 96 questionnaire-based), introducing heterogeneity in case definition and clinical severity across sites.,Comorbidity data were not available from all 17 research sites, limiting the completeness of comorbidity-adjusted sensitivity analyses.,The ENIGMA brain age model was trained on a separate normative population; model generalizability across diverse demographic and cultural backgrounds represented in 17 international sites is uncertain.,Effect sizes are small (Cohen's d = 0.14 in the key subgroup), raising questions about clinical significance even where statistical significance is achieved.,No children or adolescents were included (minimum age 22 years), limiting generalizability to the age group in which SPH most commonly onsets.,Healthy controls were required to be free of all past and current mental disorders, creating a highly selected comparator group that may not reflect typical clinical populations.,Brain-PAD is a global, aggregate metric; region-specific brain age differences in SPH may be missed by this approach.,Potential residual confounding from medication use and comorbid psychopathology not captured across all sites.,Multi-source public funding reduces but does not eliminate potential conflicts; lead author funding from Boehringer Ingelheim Fonds (pharmaceutical industry-adjacent foundation) should be noted. __BOTTOM_LINE_CATEGORY__ promising_but_preliminary __BOTTOM_LINE__ In this large international mega-analysis, specific phobia was not associated with global accelerated brain aging across the full adult age spectrum, representing an important null finding. However, a robust diagnosis-by-age interaction—most evident in formally diagnosed younger adults (22–35 years)—suggests a subtle advanced brain-PAD of approximately +1.2 years (d = 0.14) that warrants longitudinal investigation but is too small and exploratory to inform current clinical practice. Clinicians should not use brain age metrics to screen, risk-stratify, or monitor patients with specific phobia at this time.