📄 psychiatry and clinical psychology

Personality Change After Traumatic Brain Injury: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis of 101 studies reveals that personality change is a common (affecting up to 68.1% of patients) and persistent consequence of traumatic brain injury, yet critical gaps remain in understanding its precise characteristics, lesion associations, and effective treatments due to inconsistent definitions and a lack of high-quality research.

Original authors: Burns, L., Jones, K., Kerr, K., Brennan, N., Clapshaw, N., Green, H., Farrimond, H., Stone, C., Wilkinson, S., Members of Headway London,, Bell, V.

Published 2026-07-02

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: Burns, L., Jones, K., Kerr, K., Brennan, N., Clapshaw, N., Green, H., Farrimond, H., Stone, C., Wilkinson, S., Members of Headway London,, Bell, V.

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ⚕️ This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer

The Big Picture: A "Software Glitch" After a "Hardware Crash"

Imagine your brain is a highly sophisticated computer. When someone suffers a Traumatic Brain Injury (TBI), it's like that computer has been dropped, smashed, or hit by a lightning bolt. The physical damage (the "hardware") is obvious, but this study focuses on the "software" that runs afterwards: personality.

The researchers wanted to answer three big questions:

How often does the "software" change after the crash?
What does that change actually look like?
Can we fix it?

The Findings: How Common is the Change?

The team looked at 101 different studies (a massive library of research) to get a clear picture. They found that personality changes are incredibly common, but measuring them is tricky because everyone uses different rulers.

The "Strict" Ruler: If you look only for a formal diagnosis of a "Personality Disorder" (like a specific error code), about 29% of people get it.
The "Broad" Ruler: If you look for any noticeable shift in how a person acts, feels, or interacts, the number jumps to about 68%.

The Catch: The "Broad" number is a bit wobbly. The researchers compared it to a house built on shifting sand; when they adjusted for flaws in the studies or removed one weird outlier, the number dropped significantly. So, while we know personality changes happen a lot, the exact percentage is hard to pin down. However, a safe bet is that roughly one in three to one in two people will experience some form of personality shift after a brain injury.

What Does the "Glitch" Look Like?

The study didn't just find one type of change; it found a whole menu of symptoms. Think of it like a car that used to drive smoothly but now has a few different issues:

The "Short Fuse": Irritability, anger outbursts, and frustration are the most common complaints.
The "Emotional Rollercoaster": Mood swings, anxiety, and depression.
The "Social Withdrawal": People pulling away from friends and family, or acting socially awkward.
The "Impulse Control Failure": Doing things without thinking, being restless, or making poor decisions.
The "Energy Drain": Fatigue and lack of motivation.

A Key Insight from Real People: The researchers worked with people who have actually lived through brain injuries. These "experts by experience" pointed out that fatigue and depression are huge parts of the personality change. They explained that when you are exhausted and sad, you naturally have less patience and energy for socializing, which looks like a personality change even if the core "self" is just tired.

The Mystery of the "Broken Circuit" (Lesion Location)

You might think, "If the front of the brain is hit, the personality changes." While that's often true, the study found the map is much messier than expected.

The Old Map: Doctors used to think only the frontal lobe (the CEO of the brain) was responsible for personality.
The New Reality: The study found that changes can happen with damage to the temporal lobes (sides), bilateral (both sides), and even other areas.
The Problem: The studies looking at this were often small or poorly designed. It's like trying to figure out which specific wire caused a house fire by looking at a blurry photo. The researchers concluded that we simply don't have a clear map yet connecting specific brain damage to specific personality traits.

The Treatment Gap: "We Know It's Broken, But We Don't Have the Fix"

This is the most concerning part of the paper.

Medication: There are no high-quality trials proving that specific drugs fix "personality change" as a whole. Doctors are currently just guessing, using mood stabilizers or antipsychotics to treat individual symptoms (like anger or anxiety) rather than the root personality issue.
Therapy: There is almost no research on psychological therapies specifically designed to fix post-injury personality changes.
The Family Factor: The study noted that families often struggle because the person with the injury and their loved ones often disagree on what has changed. One person might feel fine, while their spouse feels they are living with a stranger.

The Bottom Line

Personality change after a brain injury is common, persistent, and often permanent. It doesn't just fade away after a few months; it can last for years or decades.

However, the medical world is currently flying blind. We don't have a standard definition for what "personality change" means, we don't have a perfect map of which brain damage causes which change, and we have very few proven treatments to help people and their families cope with it.

The researchers conclude that while we know the problem is huge, we urgently need better tools to define it and better methods to treat it. Until then, families are often left trying to navigate a new, difficult reality without a manual.

Technical Summary: Personality Change After Traumatic Brain Injury

Problem Statement
Personality change following traumatic brain injury (TBI) is recognized as a debilitating consequence that significantly impacts social adjustment, family life, and rehabilitation outcomes. Despite its clinical significance, the condition remains poorly understood due to inconsistent definitions, a lack of systematic synthesis regarding long-term prognosis, and an absence of evidence-based treatment protocols. Furthermore, while acquired personality change is traditionally linked to prefrontal cortex damage, the specific lesion locations associated with post-TBI personality change remain unclear, particularly given that other forms of acquired brain injury suggest a broader range of associated lesions. There is a critical need to synthesize existing literature to clarify the prevalence, characteristics, persistence, and neuroanatomical correlates of this condition.

Methodology
This study is a pre-registered (CRD42023440990) systematic review and meta-analysis conducted in compliance with PRISMA 2020 guidelines. The authors searched four databases (MEDLINE, PsycINFO, EMBASE, and CINAHL) for peer-reviewed primary studies published in English between July 1980 and November 2023 (updated June 2025).

Inclusion Criteria: Studies involving adult human participants (16+) with TBI (ranging from mild to severe, including closed or penetrating injuries) that explicitly assessed personality change, secondary personality disorder, or specific personality constructs.
Exclusion Criteria: Reviews, non-English publications, animal studies, pediatric-exclusive research, and studies focusing solely on impulsivity, identity, or cognition without explicit mention of personality change.
Data Synthesis: The review included 101 studies. Prevalence estimates were derived using a random-effects meta-analysis with the Paule–Mandel estimator. Heterogeneity was assessed using $I^2$ and $\tau^2$ . Publication bias was evaluated using Doi plots and the LFK index, as funnel plots are deemed inappropriate for prevalence meta-analyses. Robustness analyses included outlier removal, leave-one-out sensitivity analyses, trim-and-fill adjustments, and meta-regression to account for risk of bias and study design variables. Risk of bias was assessed using the Joanna Briggs Institute (JBI) critical appraisal tools.

Key Contributions and Results

Conceptualization and Symptoms:
The review identified 101 studies, revealing significant inconsistency in how personality change is defined. However, a narrative synthesis of symptoms (Table 1) highlighted common domains:
- Mood/Emotional Regulation: Irritability/frustration ( $k=21$ ), mood swings/emotional instability ( $k=17$ ), anger outbursts ( $k=14$ ), and anxiety ( $k=12$ ).
- Behavioral Dysregulation: Impulsivity ( $k=13$ ), restlessness/sleep disturbance ( $k=10$ ), and aberrant motor behaviors ( $k=10$ ).
- Social/Interpersonal: Decreased social interaction and withdrawal ( $k=13$ ).
- Psychopathology: Depression ( $k=17$ ) and various personality disorder diagnoses were frequently reported.
  Notably, the authors observed that constructs such as fatigue, depression, and addiction were often included under the umbrella of personality change, despite not being traditional personality traits.
Prevalence Estimates:
Meta-analysis was performed on 17 studies. The authors distinguished between "broad personality change" and "secondary personality disorder diagnosis" due to high heterogeneity ( $I^2 = 95.1\%$ ) when combined.
- Secondary Personality Disorder: The estimated prevalence was 29.1% (95% CI: 22.5% – 36.2%). This estimate remained relatively stable across robustness analyses, including adjustments for risk of bias and publication bias.
- Broad Personality Change: The initial estimate was 68.1% (95% CI: 53.4% – 81.2%). However, this figure proved highly unstable. After removing a significant outlier, the estimate rose to 73.7% with reduced heterogeneity. Conversely, adjusting for publication bias (trim-and-fill) lowered the estimate to 42.5%. Adjusting for risk of bias further altered the estimate to 51.2%. The authors conclude that the broad personality change estimate is unreliable and should be treated with caution.
Longitudinal Outcomes:
Longitudinal studies, though often small and of varying quality, consistently indicated that personality changes remain stable over long follow-up periods (ranging from 2 years to over 60 years in case studies). Changes do not appear to be transient; rather, they persist into the chronic phase, with some studies showing rates of change remaining high (e.g., 60–74%) even 5 to 10 years post-injury.
Lesion Location:
The relationship between specific lesion locations and personality dimensions remains unclear due to poor methodological quality and small sample sizes in existing studies. While frontal lobe involvement was common across dimensions, specific patterns emerged in case studies:
- Orbitofrontal lesions were frequently associated with emotional lability and disinhibition.
- Temporal lobe lesions appeared in cases of irritability and aggression.
- Bilateral lesions were common in aggression and mood changes.
  However, the authors state that firm conclusions regarding lesion-personality mapping cannot be drawn from the current literature.
Treatment Evidence:
The review found a striking lack of systematic evidence for treatments.
- Pharmacology: No controlled trials were identified. Retrospective data suggested the use of mood stabilizers, antipsychotics, and antidepressants for symptom management, but these were not systematic investigations of personality change as a primary outcome.
- Non-Pharmacological: Evidence is limited to uncontrolled studies and case reports involving neurorehabilitation, psychotherapy, and repetitive transcranial magnetic stimulation (rTMS). No reports of psychological interventions specifically targeting post-TBI personality change were found.

Significance and Claims
The paper claims that personality change is a common and persistent consequence of TBI, affecting roughly one-third to one-half of patients based on conservative estimates. The authors emphasize that the condition is as common as, if not more common than, cognitive impairment or affective disorders post-TBI.

The primary significance of this work lies in highlighting critical gaps in the field:

Definitional Ambiguity: The lack of a unified definition hinders comparable prevalence reporting and clinical consensus.
Methodological Limitations: The instability of the broad prevalence estimate and the inability to map lesions reliably underscore the need for higher-quality, standardized studies.
Treatment Void: The most concerning finding is the scarcity of systematic studies addressing treatment. The authors note that current clinical practice often treats component symptoms (e.g., irritability) rather than the overarching personality syndrome.

The authors conclude that while personality change is a major source of disability, it remains poorly addressed clinically. They advocate for the development of targeted interventions for both individuals and their families, noting that family dynamics and relationship deterioration are significant priorities identified by lived experience collaborators. The paper does not propose new experimental protocols but calls for the establishment of evidence-based therapies and better outcome measures to guide future research.