Rebecca Girlinghouse, MA
WKPIC Doctoral Intern
This study sought to replicate findings from the literature on psychotic disorder due to traumatic brain injury (PD-TBI) and explore characteristics that may assist in differentiating PD-TBI from schizophrenia. The authors argue that studies conducted over the past few decades have demonstrated that TBI, coupled with a genetic predisposition for schizophrenia, increases the odds for developing a psychotic disorder. However, other authors criticized these findings, arguing that past studies were unreliable due to methodological weaknesses. They argued that psychosis is a risk factor for sustaining a TBI and not vice versa. Given these criticisms, the authors of the current study sought to update their findings on PD-TBI, which were published in the early 2000s.
For their study, the authors obtained case studies from various psychiatric and neurological publications. Case studies were included if the subject developed psychosis following TBI and met the DSM-IV criteria for Psychotic Disorder Due to a General Medical Condition. Exclusion criteria were subjects with a history of psychosis before TBI, cases originally used in the authors’ previous studies, and case studies published in journals written in another language other than English.
The authors examined a total of 30 articles with 64 cases. The severity of TBI was based on established criteria in which a head injury is considered mild if duration of loss of consciousness is 30 minutes or less. The sample consisted of 56 men and 8 women. Causes of TBI, in order of frequency, were motor vehicle accidents, assault, falls, gunshot wounds, and unspecified. Most (91%) were closed head injuries.
After analysis of the cases, the authors reported a variety of findings that, overall, supported their previous studies. First, they found that PD-TBI can result from all TBIs, regardless of severity. However, most individuals who developed psychosis following TBI experienced loss of consciousness after their injury. Second, the data suggested the mean latency for onset of psychotic disorder following TBI was 3.6 years. Third, the authors noted that males have a significantly higher risk to develop PD-TBI, even when analyses were controlled for the overrepresentation of men in the sample. Additionally, those with a family history were found to be more at risk of developing psychotic disorder following TBI.
The authors also found that seizures are more common in those who develop a psychotic disorder following TBI than those who do not. Additionally, data suggested those with PD-TBI most often experience delusions (92%), with persecutory content (77%) as well as hallucinations (87%) that are auditory in nature (92%). Of note, individuals with PD-TBI are less likely to experience negative symptoms (37%) when compared to those with schizophrenia. Furthermore, when negative symptoms are present in those with PD-TBI, the most common type is blunted affect while the most common type in those with schizophrenia is social withdrawal. Individuals with PD-TBI, like those with schizophrenia, also tend to show impairment in neuropsychological functioning, most commonly in the areas of executive functioning and memory. However, they do not often evidence deficits in vocabulary and verbal skills.
Results of neurological testing also suggest differences between those with PD-TBI and schizophrenia. Individuals diagnosed with PD-TBI are more likely to show positive findings on MRI/CT scans. Further, these findings tend to be more focal in nature, with lesions in the frontal and temporal lobes being most prevalent. In contrast, those with schizophrenia show whole-brain involvement, hippocampal atrophy, and enlarged ventricles. Additionally, the most common EEG finding in those with PD-TBI is temporal spiking or slowing, whereas individuals diagnosed with schizophrenia show general slowing.
Given the findings from this study, as well as similar findings in the literature, the authors argue that there is evidence suggesting PD-TBI is a distinct subtype of psychotic disorder. Further, PD-TBI tends to have a less severe presentation than schizophrenia, as negative symptoms and difficulties with verbal abilities are less common. This is likely due to the fact that those with schizophrenia evidence global brain abnormalities while those with PD-TBI often have abnormalities in specific regions of the brain. However, even though there appears to be underlying differences in the disease process between those with PD-TBI and schizophrenia, the authors conclude the most efficacious treatment continues to be decreasing positive symptoms with antipsychotic medication.
There are several limitations to this study that should be mentioned. First, the authors noted there were missing data due to differences in the way cases were described in the various studies they analyzed. Therefore, the sample sizes for specific characteristics of PD-TBI were highly variable and often less than 64. This limitation, then, can threaten internal and external validity. Second, metanalysis always comes with an increased risk of bias, as oftentimes only articles reporting significant findings are published. Third, the authors had to base their comparisons of PD-TBI and schizophrenia on descriptive statistics used in each study they analyzed and, therefore, were not able to use inferential statistical analysis.
Overall, the article was helpful in further building the case that PD-TBI is a disorder separate from schizophrenia. Additionally, it provides valuable information regarding possible characteristics for differential diagnosis between PD-TBI and schizophrenia. Future research could add to the already existing literature by continuing to build evidence supporting PD-TBI as its own disorder and identifying characteristics helpful for differential diagnosis. Additionally, it would be interesting to determine if these findings hold up when using the criteria in the DSM-V. The authors also propose that research examine possible prodromal symptoms that may occur between TBI and onset of psychosis and determine if they mirror the prodromal period preceding first episode psychosis in schizophrenia. Furthermore, it may be helpful to examine if there are therapeutic interventions that may be efficacious for those with PD-TBI, now that the literature provides a better understanding of the etiology and characteristics of the disorder.
Fujii, D. & Fujii, D. (2012). Psychotic disorder due to traumatic brain injury: Analysis of case studies in the literature. The Journal of Neuropsychiatry and Clinical Neurosciences, 24(3), 278-289.