Traumatic brain injury (TBI) is a significant public health concern, often resulting in cognitive, emotional, and behavioral changes that impact quality of life (1, 2). Personality changes following TBI are particularly critical, as they can affect interpersonal relationships, occupational functioning, and psychological well-being (3, 4). The NEO-Five Factor Inventory-3 (NEO-FFI-3), based on the Five-Factor Model, provides a robust framework for assessing personality traits: Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Conscientiousness (5). Prior studies have reported mixed findings, with some indicating increased Neuroticism and reduced Agreeableness post-TBI, while others suggest variable changes depending on injury severity and socio-demographic factors (6, 7). Socio-demographic characteristics, such as education, employment, and locality, may modulate post-TBI personality changes by influencing cognitive reserve, social support, and access to rehabilitation (1,8,9). For instance, lower education levels and unemployment may exacerbate declines in Conscientiousness due to reduced cognitive and occupational engagement (4). Rural settings, common in low-resource regions, may limit access to specialized care, potentially amplifying personality changes (2). However, longitudinal studies examining these influences in diverse populations remain limited, particularly in rural, less-educated cohorts. This study aimed to investigate longitudinal personality changes in TBI patients over 18 months using the NEO-FFI-3 and to explore the impact of socio-demographic factors, including age, gender, education, marital status, occupation, family type, and locality. We hypothesized those significant changes in personality traits would occur, with socio-demographic factors like lower education and unemployment associated with greater declines in adaptive traits like Conscientiousness and Agreeableness.

Study Design and Participants This longitudinal study followed 200 individuals diagnosed with TBI, recruited from a tertiary care hospital between January 2023 and June 2023. Participants were assessed at three time points: baseline (0 months, within one month of injury), 6 months, and 18 months post-injury. Inclusion criteria included a confirmed TBI diagnosis, age ≥18 years, and ability to complete the NEO-FFI-3. Exclusion criteria included pre-existing neurological or psychiatric disorders, severe cognitive impairment precluding assessment, or inability to provide informed consent. Ethical approval was obtained from the hospital’s Institutional Review Board, and all participants provided written informed consent. Measures Personality Assessment Personality traits were measured using the NEO-Five Factor Inventory-3 (NEO-FFI-3), a 60-item self-report questionnaire assessing five domains: Neuroticism (emotional instability), Extraversion (sociability), Openness to Experience (intellectual curiosity), Agreeableness (cooperativeness), and Conscientiousness (organization). Scores range from 0 to 48 per domain, with higher scores indicating greater expression of the trait (5). The NEO-FFI-3 was administered at each time point, and responses were categorized into Very Low, Low, Average, High, and Very High based on standardized norms. Socio-Demographic Characteristics Socio-demographic data were collected at baseline via a structured questionnaire, including age (≥18 years, categorized as 31–45 years, ≥46 years in analysis), gender (male, female), education (≤V standard, VI–X standard, graduate, post-graduate), marital status (single, married, divorced, widowed), occupation (unemployed, employed, self-employed), family type (nuclear, extended), and locality (urban, rural). The variable dictionary below summarizes these measures. Procedure Participants completed the NEO-FFI-3 at each time point under the supervision of trained research assistants. Socio-demographic data were collected at baseline. Follow-up assessments were conducted in-person or via telephonic interviews for rural participants unable to travel. Data were de-identified and stored securely to ensure confidentiality. Statistics All statistical analyses were performed with SPSS 19.0 software (SPSS Inc., IBM, Chicago, IL, USA)and R version 4.4.1. Descriptive statistics (frequencies, percentages) were used to summarize socio-demographic characteristics and NEO-FFI-3 categorical distributions. Continuous variables, such as age and NEO-FFI-3 scores, were reported as means and standard deviations where appropriate. Proportions and their 95% confidence intervals were estimated using the Wilson method. Within-subject changes in NEO-FFI-3 scores over time (0, 6, and 18 months) were analyzed using one-way repeated-measures ANOVA, with Time as the within-subject factor. The assumption of sphericity was tested using Mauchly’s test; when violated, Greenhouse–Geisser corrections were applied. Normality of residuals was examined with the Shapiro–Wilk test, and homogeneity of variances with Levene’s test. Bonferroni-adjusted paired t-tests were conducted for post hoc pairwise comparisons to control for Type I error. Effect sizes were reported as generalized eta squared (η²g). Additionally, change scores (e.g., 18 months minus baseline) were calculated for each NEO-FFI-3 domain to assess associations with socio-demographic variables. Repeated measures correlations were conducted to assess the associations among personality domain scores across time points. This approach accounted for within-subject consistency and explored co-variation between traits longitudinally. Statistical significance was set at p< 0.05.

Socio-Demographic Characteristics The socio-demographic profile of the sample (N=200) is presented in Table 1. The mean age was 45.2 years (SD = 8.7). Participants were predominantly male (58%) and aged 31–45 years (51.5%) or ≥46 years (48.5%). No participants aged 18–30 years were enrolled, likely reflecting the older demographic profile of TBI patients at the tertiary care hospital and the requirement to complete the NEO-FFI-3, which may have excluded younger patients with more severe injuries. Most had low education levels (68% ≤V standard, 14% VI–X standard, 2.5% graduate, 15.5% post-graduate), were married (85%), and lived in nuclear families (58.5%). Occupationally, 53% were unemployed, 39.5% employed, and 7.5% self-employed. The majority resided in rural areas (78.5%) compared to urban areas (21.5%). Table 1: Socio-Demographic Characteristics of the Study Sample (N=200) Characteristic Category Mean (SD) or Percentage (%) Age (In years) 45.2 (8.7) 18–30 years 0.0% 31–45 years 51.5% ≥46 years 48.5% Gender Male 58.0% Female 42.0% Education ≤V standard 68.0% VI–X standard 14.0% Graduate 2.5% Marital Status Single 3.0% Married 85.0% Divorced 9.5% Widowed 2.5% Occupation Unemployed 53.0% Employed 39.5% Self-employed 7.5% Family Type Nuclear 58.5% Extended 41.5% Locality Urban 21.5% Rural 78.5% Longitudinal Changes in Personality Traits One-way repeated-measures ANOVA revealed significant within-subject changes in four NEO-FFI-3 domains (Table 2).Neuroticism did not significantly change over time (F(1.13, 224.84) = 1.82, p = 0.178, η² = 0.003), with mean scores of 22.98 ± 8.15 at baseline, 22.30 ± 7.78 at 6 months, and 21.99 ± 7.23 at 18 months. Pairwise comparisons with Bonferroni adjustment revealed no significant differences between any of the time points (p > 0.29).Extraversion did not show a significant overall change over time (F(1.09, 216.45) = 2.31, p = 0.128, η² = 0.004), with mean scores of 30.76 ± 9.18 at baseline, 31.47 ± 8.00 at 6 months, and 31.96 ± 7.50 at 18 months. Pairwise comparisons indicated no significant differences between any of the time points (p > 0.22).Openness to Experience showed a significant overall change over time (F(1.04, 207.63) = 20.88, p < 0.001, η² = 0.028), with mean scores of 27.14 ± 5.08 at baseline, 29.22 ± 6.35 at 6 months, and 29.28 ± 6.20 at 18 months. Post-hoc pairwise comparisons with Bonferroniad justment revealed significant increases from baseline to 6 months (p < 0.001) and from baseline to 18 months (p < 0.001), but no significant difference between 6 and 18 months (p = 1.000).Agreeableness showed a significant overall change over time (F(1.03, 204.56) = 10.36, p = 0.001, η² = 0.014), with mean scores of 26.28 ± 5.77 at baseline, 24.97 ± 4.96 at 6 months, and 24.94 ± 4.88 at 18 months. Post-hoc pairwise comparisons with Bonferroni adjustment indicated significant decreases from baseline to 6 months (p = 0.005) and from baseline to 18 months (p = 0.004), while no significant difference was observed between 6 and 18 months (p = 1.000).Conscientiousness showed a significant overall change over time (F(1.21, 241.15) = 23.50, p < 0.001, η² = 0.043), with mean scores of 32.98 ± 5.63 at baseline, 30.74 ± 6.20 at 6 months, and 30.14 ± 5.49 at 18 months. Post-hoc pairwise comparisons with Bonferroni adjustment indicated significant decreases from baseline to 6 months (p < 0.001), from baseline to 18 months (p < 0.001), and from 6 months to 18 months (p = 0.006). Table 2: Within-Subject Effects for NEO-FFI-3 Scores (N=200) Domain 0 Month 6 Months 18 Months F (df) η² p-value Mean ± SD Mean ± SD Mean ± SD Neuroticism 22.98 ± 8.15 a 22.3 ± 7.78 a 21.99 ± 7.23 a 1.82 (1.13, 224.84) 0.003 0.178 Extraversion 30.76 ± 9.18 a 31.47 ± 8.00 a 31.96 ± 7.50 a 2.31 (1.09, 216.45) 0.004 0.128 Openness to Experience 27.14 ± 5.08 a 29.22 ± 6.35 b 29.28 ± 6.20 b 20.88 (1.04, 207.63) 0.028 <0.001 Agreeableness 26.28 ± 5.77 a 24.97 ± 4.96 b 24.94 ± 4.88 b 10.36 (1.03, 204.56) 0.014 0.001 Conscientiousness 32.98 ± 5.63 a 30.74 ± 6.20 b 30.14 ± 5.49 c 23.50 (1.21, 241.15) 0.043 <0.001 Mean ± SD. Superscript letters indicate significant differences between time points (different letters = p < 0.05, same letters = not significant) based on Bonferroni-adjusted post-hoc tests Figure 1: Mean NEO-FFI-3 Scores over Time (0, 6, and 18 Months) The figure presents NEO-FFI-3 domain scores across three time points (baseline, 6 months, and 18 months). Each dot represents an individual participant’s score, while the black boxes indicate the mean score with its 95% confidence interval. Distinct colors are used to differentiate the three time points for each personality domain. The x-axis shows the personality domains, and the y-axis shows NEO-FFI-3 scores (ranging from 0 to 48). The figure highlights the overall stability of personality traits across the study period. Categorical distributions of NEO-FFI-3 scores further supported these trends (Table 3). For Neuroticism, the “Very High” category decreased from 16.5% at baseline to 5.0% at 18 months, while the “Average” category increased from 42.0% to 48.5%. Extraversion’s “High” category rose from 27.0% to 38.0%. Openness to Experience’s “High” category increased from 18.0% to 36.0%, and “Very High” from 0% to 6.0%. Agreeableness’s “Low” category increased from 20.5% to 40.0%, and Conscientiousness’s “Low” category rose from 14.5% to 33.0%, with “Very High” decreasing from 7.5% to 1.0%. Table 3: Categorical Distribution of NEO-FFI-3 Scores at 0, 6, and 18 Months (N=200) Domain Category 0 Months (%) 6 Months (%) 18 Months (%) Neuroticism Very Low 0.0% 2.0% 4.0% Low 13.5% 14.5% 15.0% Average 42.0% 46.0% 48.5% High 28.0% 25.5% 27.5% Very High 16.5% 12.0% 5.0% Extraversion Very Low 5.5% 4.0% 3.0% Low 15.5% 14.0% 12.0% Average 45.0% 42.0% 40.0% High 27.0% 32.0% 38.0% Very High 7.0% 8.0% 7.0% Openness to Experience Very Low 2.0% 1.0% 1.0% Low 24.5% 16.0% 15.0% Average 55.5% 41.0% 36.0% High 18.0% 36.0% 36.0% Very High 0.0% 6.0% 6.0% Agreeableness Very Low 8.0% 10.0% 12.0% Low 20.5% 34.0% 40.0% Average 38.5% 29.0% 24.0% High 5.5% 3.0% 2.0% Very High 0.0% 0.0% 0.0% Conscientiousness Very Low 4.5% 6.0% 8.0% Low 14.5% 25.0% 33.0% Average 51.5% 45.0% 37.5% High 22.0% 14.0% 11.5% Very High 7.5% 2.0% 1.0% Repeated-measures correlation coefficients (rrm) among personality domains across time Repeated-measures correlation analyses indicated several significant associations among the personality domains across time. Neuroticism was negatively correlated with Extraversion (rrm = –0.42, p < .001) and Openness (rrm = –0.27, p < .01). Extraversion was positively correlated with Openness (rrm = 0.32, p < .001). Agreeableness showed a positive association with Conscientiousness (rrm = 0.23, p < .01). All other associations were nonsignificant.

The present study provides valuable insights into the longitudinal trajectory of personality changes following traumatic brain injury (TBI) in a predominantly rural, low-resource population, utilizing the NEO-FFI-3 to track alterations across five key personality domains over 18 months. Our findings reveal a mixed pattern of stability and change: while Neuroticism and Extraversion remained relatively unchanged, Openness to Experience demonstrated a significant increase, whereas Agreeableness and Conscientiousness exhibited notable declines. These results align partially with prior literature on post-TBI personality shifts, which often highlights reductions in adaptive traits like Agreeableness and Conscientiousness due to frontal lobe disruptions and executive dysfunction (4,6,8). However, the observed increase in Openness to Experience is less commonly reported and may reflect compensatory mechanisms or adaptive responses in this cohort, such as heightened curiosity or openness to new rehabilitation strategies amid recovery (5,7). The lack of significant change in Neuroticism contrasts with some studies that report elevated emotional instability post-TBI, potentially linked to depression or anxiety (3). This stability could be attributed to the sample's socio-demographic profile, including older age (mean 45.2 years, with no participants under 31) and high marital rates (85%), which may provide social buffers against neurotic tendencies (1,8). Similarly, Extraversion's stability suggests resilience in sociability, possibly supported by nuclear family structures (58.5%) prevalent in the sample, though rural locality (78.5%) and unemployment (53%) might otherwise limit social engagement opportunities (2,6). The increase in Openness to Experience, evidenced by shifts from "Average" to "High" categories (55.5% to 36.0% at baseline vs. 18 months), may indicate neuroplasticity or environmental influences, such as exposure to medical interventions or community support in low-resource settings, fostering greater intellectual curiosity over time(1,5). Conversely, the declines in Agreeableness and Conscientiousness are consistent with TBI-related impairments in interpersonal cooperation and self-regulation, often exacerbated by prefrontal damage (1,6,7). The categorical shifts—e.g., Agreeableness's "Low" category rising from 20.5% to 40.0%, and Conscientiousness's from 14.5% to 33.0%—underscore the clinical relevance of these changes, potentially contributing to strained relationships and reduced occupational functioning (3,9). Socio-demographic factors likely played a modulating role: low education levels (68% ≤V standard) and unemployment may diminish cognitive reserve, amplifying declines in Conscientiousness by limiting opportunities for structured activities (1,6). Rural residence could further compound this through restricted access to rehabilitation, as suggested by prior research in underserved populations (2). Although specific correlations between change scores and socio-demographics were explored, the predominance of these risk factors in our sample implies they contribute to the observed patterns, warranting targeted analyses in future studies. Repeated-measures correlations among traits offer additional context on their interdependencies. The negative association between Neuroticism and both Extraversion (rrm = –0.42) and Openness (rrm = –0.27) aligns with the Five-Factor Model, where emotional stability inversely relates to outgoingness and curiosity [4]. Positive links between Extraversion and Openness (rrm = 0.32), and Agreeableness and Conscientiousness (rrm = 0.23), suggest that adaptive traits co-vary, potentially forming clusters that influence recovery trajectories (7,9). These findings extend previous cross-sectional work by demonstrating longitudinal co-variation in a TBI context. Several limitations must be acknowledged. The sample's homogeneity—older, rural, less-educated, and lacking younger adults (18–30 years)—limits generalizability, possibly due to recruitment from a tertiary hospital serving severe cases (1,2). Self-report measures like the NEO-FFI-3 may be biased by insight deficits common in TBI, and attrition or telephonic follow-ups for rural participants could introduce variability (7). Injury severity was not stratified, which may mask differential effects (6,7). Additionally, while socio-demographic associations were explored via change scores, more advanced modeling (e.g., multilevel regression) could better disentangle their impacts. Future research should incorporate diverse cohorts, objective measures (e.g., informant reports), and neuroimaging to link personality changes to brain-specific alterations (1,9). Clinically, these results emphasize the need for personality-focused interventions in TBI rehabilitation, particularly in low-resource settings. Tailored programs addressing declines in Agreeableness and Conscientiousness—such as cognitive-behavioral therapy or vocational training—could mitigate socio-demographic vulnerabilities (3,7). The increase in Openness suggests potential leverage points for engaging patients in novel therapies.

This longitudinal study demonstrates that TBI leads to significant personality alterations over 18 months, with increases in Openness to Experience and decreases in Agreeableness and Conscientiousness, while Neuroticism and Extraversion remain stable. Socio-demographic factors, including rural locality, low education, and unemployment, appear to influence these changes, highlighting vulnerabilities in underserved populations. These findings underscore the importance of integrating personality assessments into TBI care and developing customized psychological support to enhance recovery and quality of life. Future efforts should prioritize equitable access to interventions to address these persistent challenges.

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