Traumatic brain injury (TBI) is defined as temporary or permanent altered neurological states or deficits due to external forces and includes concussions, contusions and hemorrhages. In the United States, over 1.7 million people suffer from TBI and severe TBIs are the leading causes of injury-induced death and disability (Georges, 2023). Globally, an estimated 50% of the population will experience a TBI, amounting to a cost of around 400 billion USD every year (Chan, 2022). TBI-related emergency department visits and hospitalizations have also risen in the past decade, mostly due to the medicalization of brain injuries and the growing awareness of the severity of TBIs.
There are two types of injuries that can cause TBIs. Primary injuries involve direct impact on the brain, like when an athlete bumps his head against a hard surface. Secondary injuries usually occur some time after a primary injury and the brain damage is exacerbated due to some molecular or inflammatory cascade. For instance, after a brain injury, excitatory neurotransmitters are released. These neurotransmitters cause an increase in the level of intracellular calcium, leading to the activation of molecules that degrade neurons. This degradation of neurons can even lead to a breach in the blood-brain barrier (Galgano, 2017). The symptoms of TBIs include nausea, dizziness, blurred vision/hearing, memory/cognitive deficit, and emotional distress like irritability, depression or anxiety.
The most common causes of TBIs are falls and car accidents. Other causes can include sports injuries, military injuries (explosives), and physical assault. The highest occurrence of TBIs tends to occur in the 0-4 age group and the 65+ age group (Galgano, 2017). Babies are at higher risk of falling at home, and some brain injuries occur before or during delivery of the baby. Shaken baby syndrome is another potential cause of TBIs in infants. The older population are at particular risk for TBIs and TBI-related consequences, as severe injuries due to falls are much more likely and the older generation are less likely to seek professional health care after a brain injury (Kureshi, 2023). This is due to age-related physical or cognitive problems that hinder healthcare access. The adolescent age group (15-24) is also at a high risk for TBIs as they are usually the most active and more likely to be involved in sports injuries. The sports with the highest incidence of TBIs include cycling, football, baseball and basketball.
TBIs have a very broad spectrum of symptoms. Mild TBIs, known as concussion, usually do not have severe symptoms and don’t require extensive treatment. Usually there is an altered mental state after the injury, ranging from confusion to unconsciousness, but the symptoms are usually transient. Repeated concussions, however, can lead to chronic traumatic encephalopathy (CTE), which have more severe psychological and cognitive consequences. Disorganized speech, tremors, difficulty with attention and memory, and mental health disorders are some of the symptoms of CTE. Currently, there is no conclusive way of diagnosing CTE, except for a brain autopsy, which has to be done after death. CTE has also been associated with aggressive and suicidal behavior, often seen in retired boxers and NFL players (Antonius, 2014). These psychiatric disorders are responsible for a lot of the suicidal behavior seen in retired athletes, particularly boxers (Galgano, 2017).
There are other more severe TBIs that cause direct damage to brain structures and components. For instance, extra-axial hematoma results from bleeding of an artery or a vein in the brain, often caused by skull fractures. Diffuse axonal injuries (DAIs) are characterized by shearing of neuronal axons due to rapid rotational acceleration/deceleration of the head and can cause altered consciousness or even an inability to regain consciousness (Georges, 2023).
TBIs and mental health disorders have been highly linked to one another. In the first year after an injury, 77% have received a diagnosis for psychiatric disorders, like depression, anxiety, PTSD, schizophrenia and alcohol use disorder. Individuals with a history of TBIs were twice as likely to experience anxiety or depression (Kureshi, 2023). This was especially true in war veterans that experienced TBIs from combat. Military personnel that experienced TBIs were more likely to experience PTSD and have higher suicide rates (Chan, 2022).
The relationship between TBIs and mental health disorders are complex. Oftentimes, they have overlapping symptoms. Fatigue, dizziness, memory/attention deficit, and emotional instability are common symptoms of TBIs, but are also characteristic symptoms of anxiety and depression. TBIs and mental health disorders often exacerbate each other, with the causal relationship going both ways. TBIs can cause mental health disorders, and vice versa. For instance, emotional trauma from a TBI can lead to PTSD. On the other hand, behavioral problems and cognitive deficits from mental health disorders may make an individual more likely to be involved in an accident and experience a TBI.
Another complication is that both TBIs and mental health disorders have very broad spectrums in terms of their symptoms and causes. And in both cases, diagnosing a TBI or mental health disorders is often difficult as there is no universally agreed upon method of diagnosis. Unfortunately, in the current healthcare system, TBIs and mental health disorders are mostly disconnected. It is crucial to recognize that TBIs and mental health are deeply interconnected and healthcare professionals must be able to clearly communicate with one another to understand their complex relationship and effectively be able to treat both.