Organic personality disorder (OPD) or secondary personality change, is a condition described in the ICD-10 and ICD-11 respectively. It is characterized by a significant personality change featuring abnormal behavior due to an underlying traumatic brain injury or another pathophysiological medical condition affecting the brain. Abnormal behavior can include but is not limited to apathy, paranoia and disinhibition. In the ICD-10, it is described as a mental disorder and not included in the classification group of personality disorders. In the ICD-11, it is described as a syndrome. The condition has not been described in any edition of the Diagnostic and Statistical Manual of Mental Disorders. Signs and symptoms OPD is associated with a large variety of symptoms, such as deficits in cognitive function, dysfunctional/abnormal behaviour, psychosis, neurosis, higher irritability and altered emotional expression. Those with OPD can experience emotional lability, meaning that their emotional expressions are unstable and fluctuating. In addition, patients may show a reduction in ability of perseverance with goals and they disinhibition, often characterised by inappropriate sexual and antisocial behavior. Those affected can experience cognitive disturbances, suspiciousness and paranoia. Altered language processing in the brain can also occur. Furthermore, patients may show changes in their sexual preference and hyposexuality symptoms. Causes OPD is associated with "personality change due to general medical condition". The OPD is included in a group of personality and behavioural disorders - in the ICD-10 this is "Personality and behavioural disorders due to brain disease, damage and dysfunction", and in the ICD-11 this is "Secondary Mental or Behavioural Syndromes Associated with Disorders or Diseases Classified Elsewhere". This mental health disorder can be caused by disease, brain damages or dysfunctions in specific brain areas in frontal lobe. The most common reason for this profound change in personality is the traumatic brain injury. Children whose brain areas have been injured or damaged, may present with attention deficit hyperactivity disorder (ADHD), oppositional defiant disorder or OPD. OPD is most often caused by lesions in three brain areas of frontal lobe: traumatic brain injuries in orbitofrontal cortex, anterior cingulate cortex and dorsolateral prefrontal cortex. OPD may also be caused by lesions in other circumscribed brain areas. Another common feature of personality of patients with OPD is their dysfunctional and maladaptive behaviour that causes serious problems in these patients, because they face problems with pursuit and achievement of their goals. Patients with OPD express a feeling of unreasonable satisfaction and