Organic Personality Disorder: Brain Injury, Executive Functions, and Behavioural Changes

The human brain is the seat of our personality, cognition, and behaviour. When the brain sustains damage, whether through injury or illness, the consequences can ripple through every aspect of a person's life, sometimes leading to significant changes in how they think, feel, and interact with the world. This raises questions about how we classify these changes. The WHO ICD-10 diagnostic criteria classify this as "organic personality disorder." Is this term accurate? Is it truly a personality disorder in the way clinicians typically define personality disorders, or does it fall into a different category?

This article explores the complex relationship between brain function, particularly executive functions, and changes in behaviour and personality following brain damage.

The Link Between Brain Lesions and Personality Changes

Neuropsychological research, particularly studies involving patients with specific brain injuries, offers crucial insights. Studies of individuals with "circumscribed lesions to areas of prefrontal cortex" have shown that such damage can lead to a "variety of striking changes in cognition, behavior and perceived 'personality'" (Stuss and Benson, 1984). This highlights a direct link between the physical state of the brain, specifically the prefrontal cortex which is heavily involved in higher-level control, and aspects of what we consider personality.

Stuss and Benson (1984) further identified common features observed in patients following such injuries, including:

• The separation of action from knowledge (knowing what to do but being unable to do it).
• Difficulty sequencing language and behaviour.
• Problems forming and shifting cognitive "set" (adapting thinking to new rules or tasks).
• Reduced resistance to interference (easily distracted).
• Impaired monitoring of behaviour.
• An acquired attitude of indifference or apathy.

These features clearly impact how a person interacts with their environment and others, often leading observers to perceive a fundamental change in their personality.

Traumatic Brain Injury (TBI) and Interpersonal Function

Traumatic brain injury (TBI) is a significant cause of acquired brain damage. Research indicates that TBI can lead to difficulties that are often interpreted as personality shifts or deficits in social skills. For instance, individuals with TBI may experience language difficulties beyond simple aphasia, suggesting a "broader problem with communication" (Kinsella, Packer, & Olver, 1991). These communication issues, such as "over-talkativeness, tangential [speech], and inappropriate use of humour," along with traits like "self-centredness" and "a failure to ask question[s]," are frequently "construed as personality change or reduced interpersonal function" by both relatives and clinicians (Bond & Godfrey, 1997; Flanagan, McDonald, & Togher, 1995; Kinsella, Packer, & Olver, 1991; McDonald, Flanagan, Martin, & Saunders, 2004).

The Central Role of Executive Functions (EF)

Many of the cognitive and behavioural changes seen after brain injury fall under the umbrella of executive functions (EF). EF refers to a set of higher-order mental processes that control and regulate other cognitive functions and behaviours. They are essential for goal-directed activity, planning, problem-solving, self-monitoring, and adapting to new situations.

• "a number of higher-order top-down processes enabling the individual to regulate, modulate and control thoughts, behavior, and emotion in a goal-directed manner" (Cicerone et al., 2006; Friedman and Miyake, 2017).

Dysfunction in these crucial processes, often termed 'dysexecutive syndrome', is strongly linked to the behavioural and personality changes observed after brain injury. The Dysexecutive Questionnaire (DEX), a tool used to identify EF deficits in daily life, specifically inquires about everyday problems related to "emotional, personality, motivational, behavioral, or cognitive" domains (Wilson et al., 1996; Bennett et al., 2005). This reinforces the idea that problems with executive control manifest across multiple areas, including those typically associated with personality.

Impaired executive function can lead to difficulties such as:

• Problems initiating or inhibiting actions.
• Reduced ability to plan and organise.
• Inflexibility in thinking and adapting to change ("problems in forming and shifting cognitive 'set'") (Stuss and Benson, 1984).
• Poor self-monitoring and error correction.
• Difficulties with emotional regulation.
• Impaired social cognition, including understanding others' mental states (Spiers, Pouk, & Santoro, 1994; Carrion, 2010).

These EF deficits are not exclusive to acquired brain injury; they are also a component of various neurodevelopmental and mental health disorders, including attention deficit hyperactivity disorder (ADHD), schizophrenia, and bipolar disorder. This overlap suggests that executive dysfunction represents a core dimension of difficulty that cuts across traditional diagnostic categories.

Effortful Control (EC): A Related Concept

Closely related to EF is the concept of Effortful Control (EC), which originates from developmental psychology and temperament research. EC is defined as a "dispositional trait-level construct that represents the tendency to employ top-down control to self-regulate, including attentional focusing, attentional shifting, and inhibition/activation of behavior" (Nigg, 2017; Rothbart et al., 2003). It is considered a key aspect of temperament, reflecting "biologically based individual differences in reactivity and self-regulation" (Moran et al., 2013). Like EF, EC involves the deliberate control of thoughts and actions, highlighting the fundamental role of self-regulation in behaviour and, by extension, personality expression.

ICD-10 Classification of Organic Personality Disorder

The International Classification of Diseases, 10th Edition (ICD-10), provides a specific classification for "organic personality disorder." According to ICD-10, this disorder (classified as F07.0) is:

• "A disorder characterized by a significant alteration of the habitual patterns of behaviour displayed by the subject premorbidly, involving the expression of emotions, needs and impulses. Impairment of cognitive and thought functions, and altered sexuality may also be part of the clinical picture."

The ICD-10 recognises that personality changes can arise from identifiable organic causes and distinguishes these changes from what are typically considered "personality disorders." Specifically, ICD-10 classifies organic personality disorder within the category of "Mental disorders due to known physiological conditions" (F07), rather than grouping it with "specific personality disorders."

Conclusion

Organic brain damage, particularly to areas like the prefrontal cortex involved in executive functions, can cause significant changes often perceived as alterations in personality (Stuss and Benson, 1984; Kinsella, Packer, & Olver, 1991). These changes are closely tied to impairments in executive function, affecting self-regulation, emotional control, social interaction, and communication (Bond & Godfrey, 1997; Flanagan, McDonald, & Togher, 1995; McDonald, Flanagan, Martin, & Saunders, 2004; Wilson et al., 1996).

Organic Personality Disorder is a recognised condition, but it is categorised based on its aetiology—as a mental disorder due to a known physiological condition—rather than as a "specific personality disorder."

References

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