Early childhood trauma refers to psychological trauma experienced in early childhood, in a critical developmental period in a child’s life spanning from conception to the age of five. Trauma experienced in early childhood can manifest across the lifespan and is believed to be associated with a variety of health problems in later life.

Development of psychological resilience is believed to significantly reduce the effects of a childhood trauma on a child’s development.

Psychological trauma is a type of damage to the mind that occurs as a result of a severely distressing event. Trauma is often the result of an overwhelming amount of stress that exceeds one's ability to cope, or integrate the emotions involved with that experience. A traumatic event involves one's experience, or repeating events of being overwhelmed that can be precipitated in weeks, years, or even decades as the person struggles to cope with the immediate circumstances, eventually leading to serious, long-term negative consequences.

However, trauma differs between individuals, according to their subjective experiences. People will react to similar events differently. In other words, not all people who experience a potentially traumatic event will actually become psychologically traumatized. However, it is possible to develop posttraumatic stress disorder (PTSD) after being exposed to a potentially traumatic event.

This discrepancy in risk rate can be attributed to protective factors some individuals may have that enable them to cope with trauma; they are related to temperamental and environmental factors. Some examples are mild exposure to stress early in life, resilience characteristics, and active seeking of help.

People who go through these types of extremely traumatic experiences often have certain symptoms and problems afterward. The severity of these symptoms depends on the person, the type of trauma involved, and the emotional support they receive from others. Reactions to and symptoms of trauma can be wide and varied, and differ in severity from person to person. A traumatized individual may experience one or several of them.

After a traumatic experience, a person may re-experience the trauma mentally and physically, hence trauma reminders, also called triggers, can be uncomfortable and even painful. It can damage people’s sense of safety, self, self-efficacy, as well as the ability to regulate emotions and navigate relationships. They may turn to psychoactive substances including alcohol to try to escape or dampen the feelings. These triggers cause flashbacks, which are dissociative experiences where the person feels as though the events is reoccurring. They can range from distracting to complete dissociation or loss of awareness of the current context. Re-experiencing symptoms are a sign that the body and mind are actively struggling to cope with the traumatic experience.

Triggers and cues act as reminders of the trauma, and can cause anxiety and other associated emotions. Often the person can be completely unaware of what these triggers are. In many cases this may lead a person suffering from traumatic disorders to engage in disruptive or self-destructive coping mechanisms, often without being fully aware of the nature or causes of their own actions. Panic attacks are an example of a psychosomatic response to such emotional triggers.

Consequently, intense feelings of anger may frequently surface, sometimes in inappropriate or unexpected situations, as danger may always seem to be present, as much as it is actually present and experienced from past events. Upsetting memories such as images, thoughts, or flashbacks may haunt the person, and nightmares may be frequent. Insomnia may occur as lurking fears and insecurity keep the person vigilant and on the lookout for danger, both day and night. Trauma doesn't only cause changes in one's daily functions but could also lead to morphological changes. Such epigenetic changes can be passed on to the next generations, thus making genetics as one of the components of the causes of psychological trauma. However, some people are born with or later develop protective factors such as genetics and sex that help lower their risk of psychological trauma.

The person may not remember what actually happened, while emotions experienced during the trauma may be re-experienced without the person understanding why (see Repressed memory). This can lead to the traumatic events being constantly experienced as if they were happening in the present, preventing the subject from gaining perspective on the experience. This can produce a pattern of prolonged periods of acute arousal punctuated by periods of physical and mental exhaustion. This can lead to mental health disorders like acute stress and anxiety disorder, traumatic grief, undifferentiated somatoform disorder, conversion disorders, brief psychotic disorder, borderline personality disorder, adjustment disorder...etc.

In time, emotional exhaustion may set in, leading to distraction, and clear thinking may be difficult or impossible. Emotional detachment, as well as dissociation or "numbing out", can frequently occur. Dissociating from the painful emotion includes numbing all emotion, and the person may seem emotionally flat, preoccupied, distant, or cold. Dissociation includes depersonalisation disorder, dissociative amnesia, dissociative fugue, dissociative identity disorder, etc. Exposure to and re-experiencing trauma can cause neurophysiological changes like slowed myelination, abnormalities in synaptic pruning, shrinking of the hippocampus, cognitive and affective impairment. This is significant in brain scan studies done regarding higher order function assessment with children and youth who were in vulnerable environments.

Some traumatized people may feel permanently damaged when trauma symptoms do not go away and they do not believe their situation will improve. This can lead to feelings of despair, transient paranoid ideation, loss of self-esteem, profound emptiness, suicidality, and frequently depression. If important aspects of the person's self and world understanding have been violated, the person may call their own identity into question. Often despite their best efforts, traumatized parents may have difficulty assisting their child with emotion regulation, attribution of meaning, and containment of post-traumatic fear in the wake of the child's traumatization, leading to adverse consequences for the child. In such instances, it is in the interest of the parent(s) and child for the parent(s) to seek consultation as well as to have their child receive appropriate mental health services.

Symptoms of PTSD generally begin within the first 3 months after the inciting traumatic event, but may not begin until years later. In the typical case, the individual with PTSD persistently avoids trauma-related thoughts and emotions, and discussion of the traumatic event, and may even have amnesia of the event. However, the event is commonly relived by the individual through intrusive, recurrent recollections, flashbacks, and nightmares. While it is common to have symptoms after any traumatic event, these must persist to a sufficient degree (i.e., causing dysfunction in life or clinical levels of distress) for longer than one month after the trauma to be classified as PTSD (clinically significant dysfunction or distress for less than one month after the trauma may be acute stress disorder).

The diagnosis of PTSD was originally developed for adults who had suffered from a single event trauma, such as rape, or a traumatic experience during a war. However, the situation for many children is quite different. Children can suffer chronic trauma such as maltreatment, family violence, and a disruption in attachment to their primary caregiver. In many cases, it is the child's caregiver who caused the trauma. The diagnosis of PTSD does not take into account how the developmental stages of children may affect their symptoms and how trauma can affect a child’s development.

The term developmental trauma disorder (DTD) has also been suggested. This developmental form of trauma places children at risk for developing psychiatric and medical disorders. Bessel van der Kolk explains DTD as numerous encounters with interpersonal trauma such as physical assault, sexual assault, violence or death. It can also be characterized by subjective events like betrayal, defeat or shame.

Repeated traumatization during childhood leads to symptoms that differ from those described for PTSD. Cook and others describe symptoms and behavioural characteristics in seven domains:

- "Attachment" – "problems with relationship boundaries, lack of trust, social isolation, difficulty perceiving and responding to others' emotional states"

- "Biology" – "sensory-motor developmental dysfunction, sensory-integration difficulties, somatization, and increased medical problems"

- "Affect or emotional regulation" – "poor affect regulation, difficulty identifying and expressing emotions and internal states, and difficulties communicating needs, wants, and wishes"

- "Dissociation" – "amnesia, depersonalization, discrete states of consciousness with discrete memories, affect, and functioning, and impaired memory for state-based events"

- "Behavioural control" – "problems with impulse control, aggression, pathological self-soothing, and sleep problems"

- "Cognition" – "difficulty regulating attention, problems with a variety of 'executive functions' such as planning, judgement, initiation, use of materials, and self-monitoring, difficulty processing new information, difficulty focusing and completing tasks, poor object constancy, problems with 'cause-effect' thinking, and language developmental problems such as a gap between receptive and expressive communication abilities."

- "Self-concept" – "fragmented and disconnected autobiographical narrative, disturbed body image, low self-esteem, excessive shame, and negative internal working models of self".

Adults with C-PTSD have sometimes experienced prolonged interpersonal traumatization as children as well as prolonged trauma as adults. This early injury interrupts the development of a robust sense of self and of others. Because physical and emotional pain or neglect was often inflicted by attachment figures such as caregivers or older siblings, these individuals may develop a sense that they are fundamentally flawed and that others cannot be relied upon.

This can become a pervasive way of relating to others in adult life described as insecure attachment. The diagnosis of dissociative disorder and PTSD in the current DSM-5 (2013) do not include insecure attachment as a symptom. Individuals with Complex PTSD also demonstrate lasting personality disturbances with a significant risk of revictimization.

Six clusters of symptoms have been suggested for diagnosis of C-PTSD:

- alterations in regulation of affect and impulses;

- alterations in attention or consciousness;

- alterations in self-perception;

- alterations in relations with others;

- somatization;

- alterations in systems of meaning.

Experiences in these areas may include:

- Difficulties regulating emotions, including symptoms such as persistent dysphoria, chronic suicidal preoccupation, self injury, explosive or extremely inhibited anger (may alternate), or compulsive or extremely inhibited sexuality (may alternate).

- Variations in consciousness, including forgetting traumatic events (i.e., psychogenic amnesia), reliving experiences (either in the form of intrusive PTSD symptoms or in ruminative preoccupation), or having episodes of dissociation.

- Changes in self-perception, such as a chronic and pervasive sense of helplessness, paralysis of initiative, shame, guilt, self-blame, a sense of defilement or stigma, and a sense of being completely different from other human beings.

- Varied changes in the perception of the perpetrator, such as attributing total power to the perpetrator, becoming preoccupied with the relationship to the perpetrator, including a preoccupation with revenge, idealization or paradoxical gratitude, seeking approval from the perpetrator, a sense of a special relationship with the perpetrator or acceptance of the perpetrator's belief system or rationalizations.

- Alterations in relations with others, including isolation and withdrawal, persistent distrust, anger and hostility, a repeated search for a rescuer, disruption in intimate relationships and repeated failures of self-protection.

- Loss of, or changes in, one's system of meanings, which may include a loss of sustaining faith or a sense of hopelessness and despair.

- Disconnection from surroundings accompanied by feelings of terror and confusion.

Posttraumatic stress disorder (PTSD) is a mental disorder that can develop after a person is exposed to a traumatic event, such as sexual assault, warfare, traffic collisions, or other threats on a person's life. Symptoms may include disturbing thoughts, feelings, or dreams related to the events, mental or physical distress to trauma-related cues, attempts to avoid trauma-related cues, alterations in how a person thinks and feels, and an increase in the fight-or-flight response. These symptoms last for more than a month after the event. Young children are less likely to show distress but instead may express their memories through play. A person with PTSD is at a higher risk for suicide and intentional self-harm.

Most people who have experienced a traumatic event will not develop PTSD. People who experience interpersonal trauma (for example rape or child abuse) are more likely to develop PTSD, as compared to people who experience non-assault based trauma such as accidents and natural disasters. About half of people develop PTSD following rape. Children are less likely than adults to develop PTSD after trauma, especially if they are under ten years of age. Diagnosis is based on the presence of specific symptoms following a traumatic event.

Prevention may be possible when therapy is targeted at those with early symptoms but is not effective when carried out among all people following trauma. The main treatments for people with PTSD are counselling and medication. A number of different types of therapy may be useful. This may occur one-on-one or in a group. Antidepressants of the selective serotonin reuptake inhibitor type are the first-line medications for PTSD and result in benefit in about half of people. These benefits are less than those seen with therapy. It is unclear if using medications and therapy together has greater benefit. Other medications do not have enough evidence to support their use and in the case of benzodiazepines may worsen outcomes.

In the United States about 3.5% of adults have PTSD in a given year, and 9% of people develop it at some point in their life. In much of the rest of the world, rates during a given year are between 0.5% and 1%. Higher rates may occur in regions of armed conflict. It is more common in women than men. Symptoms of trauma-related mental disorders have been documented since at least the time of the ancient Greeks. During the World Wars study increased and it was known under various terms including "shell shock" and "combat neurosis". The term "posttraumatic stress disorder" came into use in the 1970s in large part due to the diagnoses of U.S. military veterans of the Vietnam War. It was officially recognized by the American Psychiatric Association in 1980 in the third edition of the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-III).

Chronic illness can affect a child’s development at any stage. During infancy and childhood chronic illness can be detrimental to the development of secure attachment, interpersonal trust, self-regulation, and/or peer relation skills. During middle adolescence, chronic illness can prevent a child from being in school on a regular basis. This can affect a child’s academic and social competence. During adolescence, chronic illness can affect the development of autonomy and self-image. It can also interfere with peer & romantic relationships, and the desire for independence can lead to poor treatment compliance.

"See Adverse Childhood Experiences Study"

Adverse childhood experiences (ACEs) are potentially traumatic events that can have negative, lasting effects on health and well-being. Adverse childhood experiences range from abuse to neglect to living in a household where the mother is treated violently or there is a parent with a mental illness. Kaiser Permanente and the Centers for Disease Control and Prevention's 1998 study on adverse childhood experiences determined that traumatic experiences during childhood are a root cause of many social, emotional, and cognitive impairments that lead to increased risk of unhealthy behaviors, risk of violence or re-victimization, chronic health conditions, low life potential and premature mortality. As the number of adverse experiences increases, the risk of problems from childhood through adulthood also rises. Nearly 30 years of study following the initial study has confirmed this. Many states, health providers, and other groups now routinely screen parents and children for ACEs.

Emotional dysregulation in children can be associated with internalizing behaviors including

- exhibiting emotions too intense for a situation

- difficulty calming down when upset

- difficulty decreasing negative emotions

- being less able to calm themselves

- difficulty understanding emotional experiences

- becoming avoidant or aggressive when dealing with negative emotions

- experiencing more negative emotions

Some common childhood onset chronic illnesses are cystic fibrosis, cerebral palsy, juvenile diabetes, juvenile rheumatoid arthritis, and cancer. Chronic illness is often a risk factor for developing psychopathologies, due to the psychological toll it takes on the children and their developing brains. Approximately 10 million children in the United States suffer from a childhood onset chronic illness.

Research has shown that failures in emotional regulation may be related to the display of acting out, externalizing disorders, or behavior problems. When presented with challenging tasks, children who were found to have defects in emotional regulation (high-risk) spent less time attending to tasks and more time throwing tantrums or fretting than children without emotional regulation problems (low-risk). These high-risk children had difficulty with self-regulation and had difficulty complying with requests from caregivers and were more defiant. Emotional dysregulation has also been associated with childhood social withdrawal. Common signs of emotional dysregulation in early childhood include isolation, throwing things, screaming, lack of eye contact, refusing to speak, rocking, running away, crying, dissociating, high levels of anxiety, or inability to be flexible.

Mental retardation is coded on Axis II of the DSM-IV-TR. The diagnostic criteria necessary in order to diagnose intellectual disability consists of:

There are varying degrees of intellectual disability, which are identified by an IQ test.

Mental retardation, Severity Unspecified: This unspecified diagnosis is given when there is a strong assumption that the child is mentally retarded, but cannot be tested because the individual is too impaired, not willing to take the IQ test or is an infant.

Mental disorders diagnosed in childhood are divided into two categories: childhood disorders and learning disorders. These disorders are usually first diagnosed in infancy, childhood, or adolescence, as laid out in the DSM IV TR and in the ICD-10. The DSM-IV-TR includes ten subcategories of disorders including Mental retardation, Learning Disorders, Motor Skills Disorders, Communication Disorders, Pervasive Developmental Disorders, Attention-Deficit and Disruptive Behavior Disorders, Feeding and Eating Disorders, Tic Disorders, Elimination Disorders, and Other Disorders of Infancy, Childhood, or Adolescence.

Dissociative disorders (DD) are conditions that involve disruptions or breakdowns of memory, awareness, identity, or perception. People with dissociative disorders use dissociation, as a defence mechanism, pathologically and involuntarily. Dissociative disorders are sometimes triggered by psychological trauma, but may be preceded only by stress, psychoactive substances, or no identifiable trigger at all.

The dissociative disorders listed in the American Psychiatric Association's DSM-5 are as follows:

- Dissociative identity disorder (formerly multiple personality disorder): the alternation of two or more distinct personality states with impaired recall among personality states. In extreme cases, the host personality is unaware of the other, alternating personalities; however, the alternate personalities can be aware of all the existing personalities. This category now includes the old derealization disorder category.

- Dissociative amnesia (formerly psychogenic amnesia): the temporary loss of recall memory, specifically episodic memory, due to a traumatic or stressful event. It is considered the most common dissociative disorder amongst those documented. This disorder can occur abruptly or gradually and may last minutes to years depending on the severity of the trauma and the patient.

- Dissociative fugue (formerly psychogenic fugue) is now subsumed under the dissociative amnesia category. It is described as reversible amnesia for personal identity, usually involving unplanned travel or wandering, sometimes accompanied by the establishment of a new identity. This state is typically associated with stressful life circumstances and can be short or lengthy.

- Depersonalization disorder: periods of detachment from self or surrounding which may be experienced as "unreal" (lacking in control of or "outside" self) while retaining awareness that this is only a feeling and not a reality.

- The old category of dissociative disorder not otherwise specified is now split into two: Other specified dissociative disorder, and unspecified dissociative disorder. These categories are used for forms of pathological dissociation that do not fully meet the criteria of the other specified dissociative disorders, or if the correct category has not been determined.

Both dissociative amnesia and dissociative fugue usually emerge in adulthood and rarely occur after the age of 50. The ICD-10 classifies conversion disorder as a dissociative disorder while the DSM-IV classifies it as a somatoform disorder.

Dissociative identity disorder (multiple personality disorder)

Cause: People with dissociative identity disorder usually have close relatives who have also had similar experiences.

Treatment: Long-term psychotherapy that helps the patient merge his/her multiple personalities into one personality. “The trauma of the past has to be explored and resolved with proper emotional expression. Hospitalization may be required if behavior becomes bizarre or destructive”. Dissociative identity disorder has a tendency to recur over a period of several years, and may become less of a problem after mid-life.

Dissociative amnesia

Cause: A way to cope with trauma.

Treatment: Psychotherapy (e.g. talk therapy) counseling or psychosocial therapy which involves talking about your disorder and related issues with a mental health provider. Psychotherapy often involves hypnosis (help you remember and work through the trauma); creative art therapy (using creative process to help a person who cannot express his or her thoughts); cognitive therapy (talk therapy to identify unhealthy and negative beliefs/behaviors); and medications (antidepressants, anti-anxiety medications or tranquilizers). These medications help control the mental health symptoms associated with the disorders, but there are no medications that specifically treat dissociative disorders. However, the medication Pentothal can sometimes help to restore the memories. The length of an event of dissociative amnesia may be a few minutes or several years. If an episode is associated with a traumatic event, the amnesia may clear up when the person is removed from the traumatic situation.

Dissociative fugue

Cause: A stressful event that happens in adulthood.

Treatment: Hypnosis is often used to help patient recall true identity and remember events of the past. Psychotherapy is helpful for the person who has traumatic, past events to resolve. Once dissociative fugue is discovered and treated, many people recover quickly. The problem may never happen again.

Depersonalization disorder

Cause: Dissociative disorders usually develop as a way to cope with trauma. The disorders most often form in children subjected to chronic physical, sexual or emotional abuse or, less frequently, a home environment that is otherwise frightening or highly unpredictable; however, this disorder can also acutely form due to severe traumas such as war or the death of a loved one.

Treatment: Same treatment as dissociative amnesia, and same drugs. An episode of depersonalization disorder can be as brief as a few seconds or continue for several years.

Compulsive hoarding, also known as hoarding disorder, is a pattern of behavior that is characterized by excessive acquisition and an inability or unwillingness to discard large quantities of objects that cover the living areas of the home and cause significant distress or impairment. Compulsive hoarding behavior has been associated with health risks, impaired functioning, economic burden, and adverse effects on friends and family members. When clinically significant enough to impair functioning, hoarding can prevent typical uses of space, enough so that it can limit activities such as cooking, cleaning, moving through the house, and sleeping. It can also put the individual and others at risk of fires, falling, poor sanitation, and other health concerns. Compulsive hoarders may be aware of their irrational behavior, but the emotional attachment to the hoarded objects far exceeds the motive to discard the items.

Researchers have only recently begun to study hoarding, and it was first defined as a mental disorder in the 5th edition of the DSM in 2013. It was not clear whether compulsive hoarding is a separate, isolated disorder, or rather a symptom of another condition, such as OCD, but the current DSM lists hoarding disorder as both a mental disability and a possible symptom for OCD. Prevalence rates have been estimated at 2% to 5% in adults, though the condition typically manifests in childhood with symptoms worsening in advanced age, at which point collected items have grown excessive and family members who would otherwise help to maintain and control the levels of clutter have either died or moved away. Hoarding appears to be more common in people with psychological disorders such as depression, anxiety and attention deficit hyperactivity disorder (ADHD). Other factors often associated with hoarding include alcohol dependence, paranoid schizotypal and avoidance traits.

In 2008, a study was conducted to determine if there is a significant link between hoarding and interference in occupational and social functioning. Hoarding behavior is often severe because hoarders do not recognize it as a problem. It is much harder for behavioral therapy to successfully treat compulsive hoarders with poor insight about their disorder. Results show that hoarders were significantly less likely to see a problem in a hoarding situation than a friend or a relative might. This is independent of OCD symptoms, as people with OCD are often very aware of their disorder, which suggests a possible association with OCPD where the behavior are ego-syntonic. The opposite condition is compulsive decluttering.

In the mid 1970s, PTS was first classified by Bryan Jennett into early and late seizures, those occurring within the first week of injury and those occurring after a week, respectively. Though the seven-day cutoff for early seizures is used widely, it is arbitrary; seizures occurring after the first week but within the first month of injury may share characteristics with early seizures. Some studies use a 30‑day cutoff for early seizures instead. Later it became accepted to further divide seizures into immediate PTS, seizures occurring within 24 hours of injury; early PTS, with seizures between a day and a week after trauma; and late PTS, seizures more than one week after trauma. Some consider late PTS to be synonymous with post-traumatic epilepsy.

Early PTS occur at least once in about 4 or 5% of people hospitalized with TBI, and late PTS occur at some point in 5% of them. Of the seizures that occur within the first week of trauma, about half occur within the first 24 hours. In children, early seizures are more likely to occur within an hour and a day of injury than in adults. Of the seizures that occur within the first four weeks of head trauma, about 10% occur after the first week. Late seizures occur at the highest rate in the first few weeks after injury. About 40% of late seizures start within six months of injury, and 50% start within a year.

Especially in children and people with severe TBI, the life-threatening condition of persistent seizure called status epilepticus is a risk in early seizures; 10 to 20% of PTS develop into the condition. In one study, 22% of children under 5 years old developed status seizures, while 11% of the whole TBI population studied did. Status seizures early after a TBI may heighten the chances that a person will suffer unprovoked seizures later.

Factitious disorder imposed on self, also known as Munchausen syndrome, is a factitious disorder wherein those affected feign disease, illness, or psychological trauma to draw attention, sympathy, or reassurance to themselves. Munchausen syndrome fits within the subclass of factitious disorder with predominantly physical signs and symptoms, but patients also have a history of recurrent hospitalization, travelling, and dramatic, extremely improbable tales of their past experiences. The condition derives its name from Baron Munchausen.

Factitious disorder imposed on self is related to factitious disorder imposed on another, which refers to the abuse of another person, typically a child, in order to seek attention or sympathy for the abuser. This drive to create symptoms for the victim can result in unnecessary and costly diagnostic or corrective procedures.

Seizures may occur after traumatic brain injury; these are known as post-traumatic seizures (PTS). However, not everyone who has post-traumatic seizures will continue to have post-traumatic epilepsy, because the latter is a chronic condition. However, the terms PTS and PTE are used interchangeably in medical literature. Seizures due to post-traumatic epilepsy are differentiated from non-epileptic post-traumatic seizures based on their cause and timing after the trauma.

A person with PTE suffers late seizures, those occurring more than a week after the initial trauma. Late seizures are considered to be unprovoked, while early seizures (those occurring within a week of trauma) are thought to result from direct effects of the injury. A provoked seizure is one that results from an exceptional, nonrecurring cause such as the immediate effects of trauma rather than a defect in the brain; it is not an indication of epilepsy. Thus for a diagnosis of PTE, seizures must be unprovoked.

Disagreement exists about whether to define PTE as the occurrence of one or more late, unprovoked seizures, or whether the condition should only be diagnosed in people with two or more. Medical sources usually consider PTE to be present if even one unprovoked seizure occurs, but more recently it has become accepted to restrict the definition of all types of epilepsy to include only conditions in which more than one occur. Requiring more than one seizure for a diagnosis of PTE is more in line with the modern definition of epilepsy, but it eliminates people for whom seizures are controlled by medication after the first seizure.

As with other forms of epilepsy, seizure types in PTE may be partial (affecting only part of one hemisphere of the brain) or generalized (affecting both hemispheres and associated with loss of consciousness). In about a third of cases, people with PTE have partial seizures; these may be simple or complex. In simple partial seizures, level of consciousness is not altered, while in complex partial seizures consciousness is impaired. When generalized seizures occur, they may start out as partial seizures and then spread to become generalized.

Post-traumatic seizures (PTS) are seizures that result from traumatic brain injury (TBI), brain damage caused by physical trauma. PTS may be a risk factor for post-traumatic epilepsy (PTE), but a person who has a seizure or seizures due to traumatic brain injury does not necessarily have PTE, which is a form of epilepsy, a chronic condition in which seizures occur repeatedly. However, "PTS" and "PTE" may be used interchangeably in medical literature.

Seizures are usually an indication of a more severe TBI. Seizures that occur shortly after a person suffers a brain injury may further damage the already vulnerable brain. They may reduce the amount of oxygen available to the brain, cause excitatory neurotransmitters to be released in excess, increase the brain's metabolic need, and raise the pressure within the intracranial space, further contributing to damage. Thus, people who suffer severe head trauma are given anticonvulsant medications as a precaution against seizures.

Around 5–7% of people hospitalized with TBI have at least one seizure. PTS are more likely to occur in more severe injuries, and certain types of injuries increase the risk further. The risk that a person will suffer PTS becomes progressively lower as time passes after the injury. However, TBI survivors may still be at risk over 15 years after the injury. Children and older adults are at a higher risk for PTS.

Post-traumatic epilepsy (PTE) is a form of epilepsy that results from brain damage caused by physical trauma to the brain (traumatic brain injury, abbreviated TBI). A person with PTE suffers repeated post-traumatic seizures (PTS, seizures that result from TBI) more than a week after the initial injury. PTE is estimated to constitute 5% of all cases of epilepsy and over 20% of cases of symptomatic epilepsy (in which seizures are caused by an identifiable organic brain condition).

It is not known how to predict who will develop epilepsy after TBI and who will not. However, the likelihood that a person will develop PTE is influenced by the severity and type of injury; for example penetrating injuries and those that involve bleeding within the brain confer a higher risk. The onset of PTE can occur within a short time of the physical trauma that causes it, or months or years after. People with head trauma may remain at a higher risk for seizures than the general population even decades after the injury. PTE may be caused by several biochemical processes that occur in the brain after trauma, including overexcitation of brain cells and damage to brain tissues by free radicals.

Diagnostic measures include electroencephalography (EEG) and brain imaging techniques such as magnetic resonance imaging, but these are not totally reliable. Antiepileptic drugs do not prevent the development of PTE after head injury, but may be used to treat the condition if it does occur. When medication does not work to control the seizures, surgery may be needed. Modern surgical techniques for PTE have their roots in the 19th century, but trepanation (cutting a hole in the skull) may have been used for the condition in ancient cultures.

According to the fifth "Diagnostic and Statistical Manual of Mental Disorders" ("DSM-5"), DID symptoms include "the presence of two or more distinct personality states" accompanied by the inability to recall personal information, beyond what is expected through normal forgetfulness. Other DSM-5 symptoms include a loss of identity as related to individual distinct personality states, and loss referring to time, sense of self and consciousness. In each individual, the clinical presentation varies and the level of functioning can change from severely impaired to adequate. The symptoms of dissociative amnesia are subsumed under the DID diagnosis but can be diagnosed separately. Individuals with DID may experience distress from both the symptoms of DID (intrusive thoughts or emotions) and the consequences of the accompanying symptoms (dissociation rendering them unable to remember specific information). The majority of patients with DID report childhood sexual or physical abuse, though the accuracy of these reports is controversial. Identities may be unaware of each other and compartmentalize knowledge and memories, resulting in chaotic personal lives. Individuals with DID may be reluctant to discuss symptoms due to associations with abuse, shame, and fear. DID patients may also frequently and intensely experience time disturbances.

Around half of people with DID have fewer than 10 identities and most have fewer than 100; as many as 4,500 have been reported. The average number of identities has increased over the past few decades, from two or three to now an average of approximately 16. However, it is unclear whether this is due to an actual increase in identities, or simply that the psychiatric community has become more accepting of a high number of compartmentalized memory components. The primary identity, which often has the patient's given name, tends to be "passive, dependent, guilty and depressed" with other personalities being more active, aggressive or hostile, and often containing a current time line that lacks childhood memory. Most identities are of ordinary people, though fictional, mythical, celebrity and animal parts have been reported.

Symptoms of a dissociative fugue include mild confusion, and once the fugue ends, possible depression, grief, shame and discomfort. People have also experienced a post-fugue anger.

The psychiatric history frequently contains multiple previous diagnoses of various disorders and treatment failures. The most common presenting complaint of DID is depression, with headaches being a common neurological symptom. Comorbid disorders can include substance abuse, eating disorders, anxiety, post traumatic stress disorder (PTSD), and personality disorders. A significant percentage of those diagnosed with DID have histories of borderline personality disorder and bipolar disorder. Further, data supports a high level of psychotic symptoms in individuals with DID, and that both individuals diagnosed with schizophrenia and those diagnosed with DID have histories of trauma. Other disorders that have been found to be comorbid with DID are somatization disorders, major depressive disorder, as well as history of a past suicide attempt, in comparison to those without a DID diagnosis. Individuals diagnosed with DID demonstrate the highest hypnotizability of any clinical population. The large number of symptoms presented by individuals diagnosed with DID has led some clinicians to suggest that, rather than being a separate disorder, diagnosis of DID is actually an indication of the severity of the other disorders diagnosed in the patient.